[libvirt PATCH 00/10] docs: Convert hacking to rst, split and rework it
hacking.html is the canonical entry point for people looking to help with libvirt's development, but its sheer size makes it a farily ineffective tool. Move most non-critical information off to separate pages and brush up what's left so that it works as a quick introduction. As a prerequisite, convert the existing page to reStructuredText. I have compared the HTML version and the conversion visually and didn't spot any massive differences, save for a few spacing changes that are not specific to the page itself but rather to the HTML generated by docutils and which will require CSS tweaks to address, which is a job I'm leaving to someone else. I have also spent very little time actually changing the contents, and mostly just moved them around. There's plenty of opportunities for improvement there, but once again that's someone else's job. Andrea Bolognani (10): docs: Convert hacking.html to reStructuredText docs: Add glib-adoption.rst docs: Add coding-style.rst docs: Add programming-languages.rst docs: Add developer-tooling.rst docs: Add committer-guidelines.rst docs: Add advanced-tests.rst docs: Add submitting-patches.rst docs: Add best-practices.rst docs: Update hacking.rst build-aux/syntax-check.mk | 4 +- docs/advanced-tests.rst | 178 ++++ docs/best-practices.rst | 37 + docs/coding-style.rst | 919 +++++++++++++++++++ docs/committer-guidelines.rst | 33 + docs/developer-tooling.rst | 13 + docs/glib-adoption.rst | 96 ++ docs/hacking.html.in | 1555 -------------------------------- docs/hacking.rst | 79 ++ docs/programming-languages.rst | 21 + docs/submitting-patches.rst | 88 ++ 11 files changed, 1466 insertions(+), 1557 deletions(-) create mode 100644 docs/advanced-tests.rst create mode 100644 docs/best-practices.rst create mode 100644 docs/coding-style.rst create mode 100644 docs/committer-guidelines.rst create mode 100644 docs/developer-tooling.rst create mode 100644 docs/glib-adoption.rst delete mode 100644 docs/hacking.html.in create mode 100644 docs/hacking.rst create mode 100644 docs/programming-languages.rst create mode 100644 docs/submitting-patches.rst -- 2.25.1
The conversion has been performed by using pandoc as a first pass, and then tweaking the result manually until it looked satisfactory. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- build-aux/syntax-check.mk | 4 +- docs/hacking.html.in | 1555 ------------------------------------- docs/hacking.rst | 1400 +++++++++++++++++++++++++++++++++ 3 files changed, 1402 insertions(+), 1557 deletions(-) delete mode 100644 docs/hacking.html.in create mode 100644 docs/hacking.rst diff --git a/build-aux/syntax-check.mk b/build-aux/syntax-check.mk index c7c938ac92..6ffea7afb9 100644 --- a/build-aux/syntax-check.mk +++ b/build-aux/syntax-check.mk @@ -2040,7 +2040,7 @@ exclude_file_name_regexp--sc_prohibit_canonicalize_file_name = \ ^(build-aux/syntax-check\.mk|tests/virfilemock\.c)$$ exclude_file_name_regexp--sc_prohibit_raw_allocation = \ - ^(docs/hacking\.html\.in|src/util/viralloc\.[ch]|examples/.*|tests/(securityselinuxhelper|(vircgroup|nss)mock|commandhelper)\.c|tools/wireshark/src/packet-libvirt\.c|tools/nss/libvirt_nss(_leases|_macs)?\.c|build-aux/useless-if-before-free)$$ + ^(docs/hacking\.rst|src/util/viralloc\.[ch]|examples/.*|tests/(securityselinuxhelper|(vircgroup|nss)mock|commandhelper)\.c|tools/wireshark/src/packet-libvirt\.c|tools/nss/libvirt_nss(_leases|_macs)?\.c|build-aux/useless-if-before-free)$$ exclude_file_name_regexp--sc_prohibit_readlink = \ ^src/(util/virutil|lxc/lxc_container)\.c$$ @@ -2048,7 +2048,7 @@ exclude_file_name_regexp--sc_prohibit_readlink = \ exclude_file_name_regexp--sc_prohibit_setuid = ^src/util/virutil\.c|tools/virt-login-shell\.c$$ exclude_file_name_regexp--sc_prohibit_snprintf = \ - ^(build-aux/syntax-check\.mk|docs/hacking\.html\.in|tools/virt-login-shell\.c)$$ + ^(build-aux/syntax-check\.mk|docs/hacking\.rst|tools/virt-login-shell\.c)$$ exclude_file_name_regexp--sc_prohibit_strtol = ^examples/.*$$ diff --git a/docs/hacking.html.in b/docs/hacking.html.in deleted file mode 100644 index 1756e84fc4..0000000000 --- a/docs/hacking.html.in +++ /dev/null @@ -1,1555 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE html> -<html xmlns="http://www.w3.org/1999/xhtml"> - <body> - <h1>Contributor guidelines</h1> - - <ul id="toc"></ul> - - <h2><a id="patches">General tips for contributing patches</a></h2> - <ol> - <li> - <p>Discuss any large changes on the mailing list first. Post patches - early and listen to feedback.</p> - </li> - - <li> - <p>Official upstream repository is kept in git - (<code>https://libvirt.org/git/libvirt.git</code>) and is browsable - along with other libvirt-related repositories - (e.g. libvirt-python) <a href="https://libvirt.org/git/">online</a>.</p> - </li> - - <li> - <p>Patches to translations are maintained via - the <a href="https://fedora.zanata.org/">zanata project</a>. - If you want to fix a translation in a .po file, join the - appropriate language team. The libvirt release process - automatically pulls the latest version of each translation - file from zanata.</p> - </li> - - <li><p>The simplest way to send patches is to use the - <a href="https://github.com/stefanha/git-publish"><code>git-publish</code></a> - tool. All libvirt-related repositories contain a config file that - tells git-publish to use the correct mailing list and subject prefix.</p> - <p>Alternatively, you may send patches using <code>git send-email</code>.</p> - <p>Also, for code motion patches, you may find that <code>git - diff --patience</code> provides an easier-to-read patch. - However, the usual workflow of libvirt developer is:</p> -<pre> - git checkout master - git pull - git checkout -t origin -b workbranch - Hack, committing any changes along the way -</pre> - <p>More hints on compiling can be - found <a href="compiling.html">here</a>. When you want to - post your patches:</p> -<pre> - git pull --rebase - (fix any conflicts) - git send-email --cover-letter --no-chain-reply-to --annotate \ - --confirm=always --to=libvir-list@redhat.com master -</pre> - <p>For a single patch you can omit - <code>--cover-letter</code>, but a series of two or more - patches needs a cover letter.</p> - <p>Note that the <code>git send-email</code> subcommand may not - be in the main git package and using it may require installation - of a separate package, for example the "git-email" package in - Fedora and Debian. If this is your first time using - <code>git send-email</code>, you might need to configure it to - point it to your SMTP server with something like:</p> -<pre> - git config --global sendemail.smtpServer stmp.youremailprovider.net -</pre> - <p>If you get tired of typing - <code>--to=libvir-list@redhat.com</code> all the time, you can - configure that to be automatically handled as well:</p> -<pre> - git config sendemail.to libvir-list@redhat.com -</pre> - <p>As a rule, patches should be sent to the mailing list only: all - developers are subscribed to libvir-list and read it regularly, so - <strong>please don't CC individual developers</strong> unless - they've explicitly asked you to.</p> - <p>Avoid using mail clients for sending patches, as most of them - will mangle the messages in some way, making them unusable for our - purposes. Gmail and other Web-based mail clients are particularly - bad at this.</p> - <p>If everything went well, your patch should show up on the - <a href="https://www.redhat.com/archives/libvir-list/">libvir-list - archives</a> in a matter of minutes; if you still can't find it on - there after an hour or so, you should double-check your setup. - <strong>Note that, if you are not already a subscriber, your very - first post to the mailing list will be - subject to moderation</strong>, and it's not uncommon for that to - take around a day.</p> - <p>Please follow this as close as you can, especially the rebase and - <code>git send-email</code> part, as it makes life easier for other - developers to review your patch set.</p> - <p>One should avoid sending patches as attachments, - but rather send them in email body along with commit message. If a - developer is sending another version of the patch (e.g. to address - review comments), they are advised to note differences to previous - versions after the <code>---</code> line in the patch so that it helps - reviewers but doesn't become part of git history. Moreover, such patch - needs to be prefixed correctly with - <code>--subject-prefix=PATCHv2</code> appended to <code>git - send-email</code> (substitute <code>v2</code> with the correct - version if needed though).</p> - </li> - - <li><p>In your commit message, make the summary line reasonably - short (60 characters is typical), followed by a blank line, - followed by any longer description of why your patch makes - sense. If the patch fixes a regression, and you know what - commit introduced the problem, mentioning that is useful. - If the patch resolves a bugzilla report, mentioning the URL - of the bug number is useful; but also summarize the issue - rather than making all readers follow the link. You can use - 'git shortlog -30' to get an idea of typical summary lines. - </p> - </li> - - <li><p>Contributors to libvirt projects <strong>must</strong> - assert that they are in compliance with the - <a href="https://developercertificate.org/">Developer - Certificate of Origin 1.1</a>. This is achieved by adding - a "Signed-off-by" line containing the contributor's name - and e-mail to every commit message. The presence - of this line attests that the contributor has read the - above lined DCO and agrees with its statements. - </p></li> - - <li><p>Split large changes into a series of smaller patches, - self-contained if possible, with an explanation of each patch - and an explanation of how the sequence of patches fits - together. Moreover, please keep in mind that it's required to - be able to compile cleanly (<b>including</b> <code>make - check</code> and <code>make syntax-check</code>) after each - patch. A feature does not have to work until the end of a - series, but intermediate patches must compile and not cause - test-suite failures (this is to preserve the usefulness - of <code>git bisect</code>, among other things).</p> - </li> - - <li> - <p>Make sure your patches apply against libvirt GIT. Developers - only follow GIT and don't care much about released versions.</p> - </li> - - <li><p>Run the automated tests on your code before submitting any changes. - That is: - </p> -<pre> - make check - make syntax-check - make -C tests valgrind -</pre> - <p><a href="http://valgrind.org/">Valgrind</a> is a test that checks - for memory management issues, such as leaks or use of uninitialized - variables. - </p> - - <p> - Some tests are skipped by default in a development environment, - based on the time they take in comparison to the likelihood - that those tests will turn up problems during incremental builds. - These tests default to being run when building from a - tarball or with the configure option --enable-expensive-tests; - you can also force a one-time toggle of these tests by - setting VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in: - </p> -<pre> - make check VIR_TEST_EXPENSIVE=1 -</pre> - <p> - If you encounter any failing tests, the VIR_TEST_DEBUG - environment variable may provide extra information to debug - the failures. Larger values of VIR_TEST_DEBUG may provide - larger amounts of information: - </p> - -<pre> - VIR_TEST_DEBUG=1 make check (or) - VIR_TEST_DEBUG=2 make check -</pre> - - <p> - When debugging failures during development, it is possible - to focus in on just the failing subtests by using - VIR_TEST_RANGE. I.e. to run all tests from 3 to 20 with the - exception of tests 6 and 16, use: - </p> - -<pre> - VIR_TEST_DEBUG=1 VIR_TEST_RANGE=3-5,7-20,^16 ./run tests/qemuxml2argvtest -</pre> - - <p> - Also, individual tests can be run from inside the <code>tests/</code> - directory, like: - </p> -<pre> - ./qemuxml2xmltest -</pre> - - <p> - If you are adding new test cases, or making changes that alter - existing test output, you can use the environment variable - VIR_TEST_REGENERATE_OUTPUT to quickly update the saved test data. - Of course you still need to review the changes VERY CAREFULLY to - ensure they are correct. - </p> -<pre> - VIR_TEST_REGENERATE_OUTPUT=1 ./qemuxml2argvtest -</pre> - - <p>There is also a <code>./run</code> script at the top level, - to make it easier to run programs that have not yet been - installed, as well as to wrap invocations of various tests - under gdb or Valgrind. - </p> - - <p>When running our test suite it may happen that the test result is - nondeterministic because of the test suite relying on a particular file - in the system being accessible or having some specific value. To catch - this kind of errors, the test suite has a module for that prints any - path touched that fulfils constraints described above - into a file. To enable it just set - <code>VIR_TEST_FILE_ACCESS</code> environment variable. - Then <code>VIR_TEST_FILE_ACCESS_OUTPUT</code> environment - variable can alter location where the file is stored.</p> -<pre> - VIR_TEST_FILE_ACCESS=1 VIR_TEST_FILE_ACCESS_OUTPUT="/tmp/file_access.txt" ./qemuxml2argvtest -</pre> - - </li> - <li><p>The Valgrind test should produce similar output to - <code>make check</code>. If the output has traces within libvirt - API's, then investigation is required in order to determine the - cause of the issue. Output such as the following indicates some - sort of leak: - </p> -<pre> -==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89 -==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270) -==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8) -==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410) -==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188) -==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640) -==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590) -==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100) -==5414== by 0x41E20F: virtTestRun (testutils.c:161) -==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866) -==5414== by 0x41E84A: virtTestMain (testutils.c:723) -==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so) -</pre> - <p>In this example, the <code>virDomainDefParseXML()</code> had - an error path where the <code>virDomainVideoDefPtr video</code> - pointer was not properly disposed. By simply adding a - <code>virDomainVideoDefFree(video);</code> in the error path, - the issue was resolved. - </p> - - <p>Another common mistake is calling a printing function, such as - <code>VIR_DEBUG()</code> without initializing a variable to be - printed. The following example involved a call which could return - an error, but not set variables passed by reference to the call. - The solution was to initialize the variables prior to the call. - </p> -<pre> -==4749== Use of uninitialised value of size 8 -==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so) -==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so) -==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so) -==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199) -==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814) -==4749== by 0x4C8AA96: virLogMessage (virlog.c:751) -==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225) -==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439) -==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562) -==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927) -==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467) -==4749== by 0x40AB8F: virtTestRun (testutils.c:161) -</pre> - <p>Valgrind will also find some false positives or code paths - which cannot be resolved by making changes to the libvirt code. - For these paths, it is possible to add a filter to avoid the - errors. For example: - </p> -<pre> -==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20 -==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270) -==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so) -==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1) -==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1) -==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so) -==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so) -==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so) - -</pre> - <p>In this instance, it is acceptable to modify the - <code>tests/.valgrind.supp</code> file in order to add a - suppression filter. The filter should be unique enough to - not suppress real leaks, but it should be generic enough to - cover multiple code paths. The format of the entry can be - found in the documentation found at the - <a href="http://valgrind.org/">Valgrind home page</a>. - The following trace was added to <code>tests/.valgrind.supp</code> - in order to suppress the warning: - </p> -<pre> -{ - dlInitMemoryLeak1 - Memcheck:Leak - fun:?alloc - ... - fun:call_init.part.0 - fun:_dl_init - ... - obj:*/lib*/ld-2.*so* -} -</pre> - </li> - - <li> - <p>Update tests and/or documentation, particularly if you are adding - a new feature or changing the output of a program.</p> - </li> - - <li> - <p>Don't forget to update the <a href="news.html">release notes</a> - by changing <code>docs/news.xml</code> if your changes are - significant. All user-visible changes, such as adding new XML elements - or fixing all but the most obscure bugs, must be (briefly) described - in a release notes entry; changes that are only relevant to other - libvirt developers, such as code refactoring, don't belong in the - release notes. Note that <code>docs/news.xml</code> should be updated - in its own commit not to get in the way of backports.</p> - </li> - </ol> - - <p> - There is more on this subject, including lots of links to background - reading on the subject, on - <a href="http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/"> - Richard Jones' guide to working with open source projects</a>. - </p> - - <h2><a id="lang">Language Usage</a></h2> - - <p> - The libvirt repository makes use of a large number of programming - languages. It is anticipated that in the future libvirt will adopt - use of other new languages. To reduce the overall burden on developers, - there is thus a general desire to phase out usage of some of the - existing languages. - </p> - - <p> - The preferred languages at this time are: - </p> - - <ul> - <li>C - for the main libvirt codebase. Dialect supported by - GCC/CLang only.</li> - <li>Python - for supporting build scripts / tools. Code must - run with both version 2.7 and 3.x at this time.</li> - </ul> - - <p> - Languages that should not be used for any new contributions: - </p> - - <ul> - <li>Perl - build scripts must be written in Python instead.</li> - <li>Shell - build scripts must be written in Python instead.</li> - </ul> - - <h2><a id="tooling">Tooling</a></h2> - - <p> - libvirt includes support for some useful development tools right in its - source repository, meaning users will be able to take advantage of them - without little or no configuration. Examples include: - </p> - - <ul> - <li> - <a href="https://github.com/jeaye/color_coded">color_coded</a>, - a vim plugin for libclang-powered semantic syntax highlighting; - </li> - - <li> - <a href="http://valloric.github.io/YouCompleteMe/">YouCompleteMe</a>, - a vim plugin for libclang-powered semantic code completion. - </li> - </ul> - - <h2><a id="naming">Naming conventions</a></h2> - - <p> - When reading libvirt code, a number of different naming conventions will - be evident due to various changes in thinking over the course of the - project's lifetime. The conventions documented below should be followed - when creating any entirely new files in libvirt. When working on existing - files, while it is desirable to apply these conventions, keeping a - consistent style with existing code in that particular file is generally - more important. The overall guiding principal is that every file, enum, - struct, function, macro and typedef name must have a 'vir' or 'VIR' prefix. - All local scope variable names are exempt, and global variables are exempt, - unless exported in a header file. - </p> - - <dl> - <dt>File names</dt> - <dd> - <p> - File naming varies depending on the subdirectory. The preferred - style is to have a 'vir' prefix, followed by a name which matches - the name of the functions / objects inside the file. For example, - a file containing an object 'virHashtable' is stored in files - 'virhashtable.c' and 'virhashtable.h'. Sometimes, methods which - would otherwise be declared 'static' need to be exported for use - by a test suite. For this purpose a second header file should be - added with a suffix of 'priv', e.g. 'virhashtablepriv.h'. Use of - underscores in file names is discouraged when using the 'vir' - prefix style. The 'vir' prefix naming applies to src/util, - src/rpc and tests/ directories. Most other directories do not - follow this convention. - </p> - </dd> - <dt>Enum type & field names</dt> - <dd> - <p> - All enums should have a 'vir' prefix in their typedef name, - and each following word should have its first letter in - uppercase. The enum name should match the typedef name with - a leading underscore. The enum member names should be in all - uppercase, and use an underscore to separate each word. The - enum member name prefix should match the enum typedef name. - </p> - <pre> - typedef enum _virSocketType virSocketType; - enum _virSocketType { - VIR_SOCKET_TYPE_IPV4, - VIR_SOCKET_TYPE_IPV6, - };</pre> - </dd> - <dt>Struct type names</dt> - <dd> - <p> - All structs should have a 'vir' prefix in their typedef name, - and each following word should have its first letter in - uppercase. The struct name should be the same as the typedef - name with a leading underscore. A second typedef should be - given for a pointer to the struct with a 'Ptr' suffix. - </p> - <pre> - typedef struct _virHashTable virHashTable; - typedef virHashTable *virHashTablePtr; - struct _virHashTable { - ... - };</pre> - </dd> - <dt>Function names</dt> - <dd> - <p> - All functions should have a 'vir' prefix in their name, - followed by one or more words with first letter of each - word capitalized. Underscores should not be used in function - names. If the function is operating on an object, then the - function name prefix should match the object typedef name, - otherwise it should match the filename. Following this - comes the verb / action name, and finally an optional - subject name. For example, given an object 'virHashTable', - all functions should have a name 'virHashTable$VERB' or - 'virHashTable$VERB$SUBJECT", e.g. 'virHashTableLookup' - or 'virHashTableGetValue'. - </p> - </dd> - <dt>Macro names</dt> - <dd> - <p> - All macros should have a "VIR" prefix in their name, followed - by one or more uppercase words separated by underscores. The - macro argument names should be in lowercase. Aside from having - a "VIR" prefix there are no common practices for the rest of - the macro name. - </p> - </dd> - </dl> - - <h2><a id="indent">Code indentation</a></h2> - <p> - Libvirt's C source code generally adheres to some basic code-formatting - conventions. The existing code base is not totally consistent on this - front, but we do prefer that contributed code be formatted similarly. - In short, use spaces-not-TABs for indentation, use 4 spaces for each - indentation level, and other than that, follow the K&R style. - </p> - - <p> - If you use Emacs, the project includes a file .dir-locals.el - that sets up the preferred indentation. If you use vim, - append the following to your ~/.vimrc file: - </p> -<pre> - set nocompatible - filetype on - set autoindent - set smartindent - set cindent - set tabstop=8 - set shiftwidth=4 - set expandtab - set cinoptions=(0,:0,l1,t0,L3 - filetype plugin indent on - au FileType make setlocal noexpandtab - au BufRead,BufNewFile *.am setlocal noexpandtab - match ErrorMsg /\s\+$\| \+\ze\t/ -</pre> - <p> - Or if you don't want to mess your ~/.vimrc up, you can save the above - into a file called .lvimrc (not .vimrc) located at the root of libvirt - source, then install a vim script from - http://www.vim.org/scripts/script.php?script_id=1408, - which will load the .lvimrc only when you edit libvirt code. - </p> - - <h2><a id="formatting">Code formatting (especially for new code)</a></h2> - - <p> - With new code, we can be even more strict. - Please apply the following function (using GNU indent) to any new code. - Note that this also gives you an idea of the type of spacing we prefer - around operators and keywords: - </p> - -<pre> - indent-libvirt() - { - indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \ - -sbi4 -psl -saf -sai -saw -sbi4 -ss -sc -cdw -cli4 -npcs -nbc \ - --no-tabs "$@" - } -</pre> - - <p> - Note that sometimes you'll have to post-process that output further, by - piping it through <code>expand -i</code>, since some leading TABs can get through. - Usually they're in macro definitions or strings, and should be converted - anyhow. - </p> - - <p> - Libvirt requires a C99 compiler for various reasons. However, - most of the code base prefers to stick to C89 syntax unless - there is a compelling reason otherwise. For example, it is - preferable to use <code>/* */</code> comments rather - than <code>//</code>. Also, when declaring local variables, the - prevailing style has been to declare them at the beginning of a - scope, rather than immediately before use. - </p> - - - <h2><a id="bracket_spacing">Bracket spacing</a></h2> - - <p> - The keywords <code>if</code>, <code>for</code>, <code>while</code>, - and <code>switch</code> must have a single space following them - before the opening bracket. E.g. - </p> - <pre> - if(foo) // Bad - if (foo) // Good -</pre> - - <p> - Function implementations must <strong>not</strong> have any whitespace - between the function name and the opening bracket. E.g. - </p> - <pre> - int foo (int wizz) // Bad - int foo(int wizz) // Good -</pre> - - <p> - Function calls must <strong>not</strong> have any whitespace - between the function name and the opening bracket. E.g. - </p> - <pre> - bar = foo (wizz); // Bad - bar = foo(wizz); // Good -</pre> - - <p> - Function typedefs must <strong>not</strong> have any whitespace - between the closing bracket of the function name and opening - bracket of the arg list. E.g. - </p> - <pre> - typedef int (*foo) (int wizz); // Bad - typedef int (*foo)(int wizz); // Good -</pre> - - <p> - There must not be any whitespace immediately following any - opening bracket, or immediately prior to any closing bracket. E.g. - </p> - <pre> - int foo( int wizz ); // Bad - int foo(int wizz); // Good -</pre> - - <h2><a id="comma">Commas</a></h2> - - <p> - Commas should always be followed by a space or end of line, and - never have leading space; this is enforced during 'make - syntax-check'. - </p> - <pre> - call(a,b ,c);// Bad - call(a, b, c); // Good -</pre> - - <p> - When declaring an enum or using a struct initializer that - occupies more than one line, use a trailing comma. That way, - future edits to extend the list only have to add a line, rather - than modify an existing line to add the intermediate comma. Any - sentinel enumerator value with a name ending in _LAST is exempt, - since you would extend such an enum before the _LAST element. - Another reason to favor trailing commas is that it requires less - effort to produce via code generators. Note that the syntax - checker is unable to enforce a style of trailing commas, so - there are counterexamples in existing code which do not use it; - also, while C99 allows trailing commas, remember that JSON and - XDR do not. - </p> - <pre> - enum { - VALUE_ONE, - VALUE_TWO // Bad - }; - enum { - VALUE_THREE, - VALUE_FOUR, // Good - }; -</pre> - - <h2><a id="semicolon">Semicolons</a></h2> - - <p> - Semicolons should never have a space beforehand. Inside the - condition of a <code>for</code> loop, there should always be a - space or line break after each semicolon, except for the special - case of an infinite loop (although more infinite loops - use <code>while</code>). While not enforced, loop counters - generally use post-increment. - </p> - <pre> - for (i = 0 ;i < limit ; ++i) { // Bad - for (i = 0; i < limit; i++) { // Good - for (;;) { // ok - while (1) { // Better -</pre> - <p> - Empty loop bodies are better represented with curly braces and a - comment, although use of a semicolon is not currently rejected. - </p> - <pre> - while ((rc = waitpid(pid, &st, 0) == -1) && - errno == EINTR); // ok - while ((rc = waitpid(pid, &st, 0) == -1) && - errno == EINTR) { // Better - /* nothing */ - } -</pre> - - <h2><a id="curly_braces">Curly braces</a></h2> - - <p> - Omit the curly braces around an <code>if</code>, <code>while</code>, - <code>for</code> etc. body only when both that body and the condition - itself occupy a single line. In every other case we require - the braces. This ensures that it is trivially easy to identify a - single-<i>statement</i> loop: each has only one <i>line</i> in its body. - </p> - -<pre> - while (expr) // single line body; {} is forbidden - single_line_stmt(); -</pre> - -<pre> - while (expr(arg1, - arg2)) // indentation makes it obvious it is single line, - single_line_stmt(); // {} is optional (not enforced either way) -</pre> - -<pre> - while (expr1 && - expr2) { // multi-line, at same indentation, {} required - single_line_stmt(); - } -</pre> - - <p> - However, the moment your loop/if/else body extends on to a second - line, for whatever reason (even if it's just an added comment), then - you should add braces. Otherwise, it would be too easy to insert a - statement just before that comment (without adding braces), thinking - it is already a multi-statement loop: - </p> - -<pre> - while (true) // BAD! multi-line body with no braces - /* comment... */ - single_line_stmt(); -</pre> - <p> - Do this instead: - </p> -<pre> - while (true) { // Always put braces around a multi-line body. - /* comment... */ - single_line_stmt(); - } -</pre> - <p> - There is one exception: when the second body line is not at the same - indentation level as the first body line: - </p> -<pre> - if (expr) - die("a diagnostic that would make this line" - " extend past the 80-column limit")); -</pre> - - <p> - It is safe to omit the braces in the code above, since the - further-indented second body line makes it obvious that this is still - a single-statement body. - </p> - - <p> - To reiterate, don't do this: - </p> - -<pre> - if (expr) // BAD: no braces around... - while (expr_2) { // ... a multi-line body - ... - } -</pre> - - <p> - Do this, instead: - </p> - -<pre> - if (expr) { - while (expr_2) { - ... - } - } -</pre> - - <p> - However, there is one exception in the other direction, when even a - one-line block should have braces. That occurs when that one-line, - brace-less block is an <code>if</code> or <code>else</code> - block, and the counterpart block <b>does</b> use braces. In - that case, put braces around both blocks. Also, if - the <code>else</code> block is much shorter than - the <code>if</code> block, consider negating the - <code>if</code>-condition and swapping the bodies, putting the - short block first and making the longer, multi-line block be the - <code>else</code> block. - </p> - -<pre> - if (expr) { - ... - ... - } - else - x = y; // BAD: braceless "else" with braced "then", - // and short block last - - if (expr) - x = y; // BAD: braceless "if" with braced "else" - else { - ... - ... - } -</pre> - - <p> - Keeping braces consistent and putting the short block first is - preferred, especially when the multi-line body is more than a - few lines long, because it is easier to read and grasp the semantics of - an if-then-else block when the simpler block occurs first, rather than - after the more involved block: - </p> - -<pre> - if (!expr) { - x = y; // putting the smaller block first is more readable - } else { - ... - ... - } -</pre> - - <p> - But if negating a complex condition is too ugly, then at least - add braces: - </p> - -<pre> - if (complex expr not worth negating) { - ... - ... - } else { - x = y; - } -</pre> - - <p>Use hanging braces for compound statements: the opening brace - of a compound statement should be on the same line as the - condition being tested. Only top-level function bodies, nested - scopes, and compound structure declarations should ever have { - on a line by itself. - </p> - -<pre> - void - foo(int a, int b) - { // correct - function body - int 2d[][] = { - { // correct - complex initialization - 1, 2, - }, - }; - if (a) - { // BAD: compound brace on its own line - do_stuff(); - } - { // correct - nested scope - int tmp; - if (a < b) { // correct - hanging brace - tmp = b; - b = a; - a = tmp; - } - } - } -</pre> - - <h2><a id="conditions">Conditional expressions</a></h2> - <p>For readability reasons new code should avoid shortening comparisons - to 0 for numeric types. Boolean and pointer comparisions may be - shortened. All long forms are okay: - </p> -<pre> - virFooPtr foos = NULL; - size nfoos = 0; - bool hasFoos = false; - -GOOD: - if (!foos) - if (!hasFoos) - if (nfoos == 0) - if (foos == NULL) - if (hasFoos == true) - -BAD: - if (!nfoos) - if (nfoos) -</pre> - <p>New code should avoid the ternary operator as much as possible. - Specifically it must never span more than one line or nest: - </p> -<pre> -BAD: - char *foo = baz ? - virDoSomethingReallyComplex(driver, vm, something, baz->foo) : - NULL; - - char *foo = bar ? bar->baz ? bar->baz->foo : "nobaz" : "nobar"; -</pre> - - <h2><a id="preprocessor">Preprocessor</a></h2> - - <p>Macros defined with an ALL_CAPS name should generally be - assumed to be unsafe with regards to arguments with side-effects - (that is, MAX(a++, b--) might increment a or decrement b too - many or too few times). Exceptions to this rule are explicitly - documented for macros in viralloc.h and virstring.h. - </p> - - <p> - For variadic macros, stick with C99 syntax: - </p> -<pre> - #define vshPrint(_ctl, ...) fprintf(stdout, __VA_ARGS__) -</pre> - - <p>Use parenthesis when checking if a macro is defined, and use - indentation to track nesting: - </p> -<pre> - #if defined(HAVE_POSIX_FALLOCATE) && !defined(HAVE_FALLOCATE) - # define fallocate(a, ignored, b, c) posix_fallocate(a, b, c) - #endif -</pre> - - <h2><a id="types">C types</a></h2> - - <p> - Use the right type. - </p> - - <h3>Scalars</h3> - - <ul> - <li>If you're using <code>int</code> or <code>long</code>, odds are - good that there's a better type.</li> - <li>If a variable is counting something, be sure to declare it with an - unsigned type.</li> - <li>If it's memory-size-related, use <code>size_t</code> (use - <code>ssize_t</code> only if required).</li> - <li>If it's file-size related, use uintmax_t, or maybe <code>off_t</code>.</li> - <li>If it's file-offset related (i.e., signed), use <code>off_t</code>.</li> - <li>If it's just counting small numbers use <code>unsigned int</code>; - (on all but oddball embedded systems, you can assume that that - type is at least four bytes wide).</li> - <li>If a variable has boolean semantics, give it the <code>bool</code> type - and use the corresponding <code>true</code> and <code>false</code> macros. - </li> - <li>In the unusual event that you require a specific width, use a - standard type like <code>int32_t</code>, <code>uint32_t</code>, - <code>uint64_t</code>, etc.</li> - <li>While using <code>bool</code> is good for readability, it comes with - minor caveats: - <ul> - <li>Don't use <code>bool</code> in places where the type size must be constant across - all systems, like public interfaces and on-the-wire protocols. Note - that it would be possible (albeit wasteful) to use <code>bool</code> in libvirt's - logical wire protocol, since XDR maps that to its lower-level <code>bool_t</code> - type, which <b>is</b> fixed-size.</li> - <li>Don't compare a bool variable against the literal, <code>true</code>, - since a value with a logical non-false value need not be <code>1</code>. - I.e., don't write <code>if (seen == true) ...</code>. Rather, - write <code>if (seen)...</code>.</li> - </ul> - </li> - </ul> - - <p> - Of course, take all of the above with a grain of salt. If you're about - to use some system interface that requires a type like <code>size_t</code>, - <code>pid_t</code> or <code>off_t</code>, use matching types for any - corresponding variables. - </p> - - <p> - Also, if you try to use e.g., <code>unsigned int</code> as a type, and that - conflicts with the signedness of a related variable, sometimes - it's best just to use the <b>wrong</b> type, if <i>pulling the thread</i> - and fixing all related variables would be too invasive. - </p> - - <p> - Finally, while using descriptive types is important, be careful not to - go overboard. If whatever you're doing causes warnings, or requires - casts, then reconsider or ask for help. - </p> - - <h3>Pointers</h3> - - <p> - Ensure that all of your pointers are <i>const-correct</i>. - Unless a pointer is used to modify the pointed-to storage, - give it the <code>const</code> attribute. That way, the reader knows - up-front that this is a read-only pointer. Perhaps more - importantly, if we're diligent about this, when you see a non-const - pointer, you're guaranteed that it is used to modify the storage - it points to, or it is aliased to another pointer that is. - </p> - - <h2><a id="attribute_annotations">Attribute annotations</a></h2> - <p> - Use the following annotations to help the compiler and/or static - analysis tools understand the code better: - </p> - - <table class="top_table"> - <tr><th>Macro</th><th>Meaning</th></tr> - <tr><td><code>ATTRIBUTE_NONNULL</code></td><td>passing NULL for this parameter is not allowed</td></tr> - <tr><td><code>ATTRIBUTE_PACKED</code></td><td>force a structure to be packed</td></tr> - <tr><td><code>G_GNUC_FALLTHROUGH</code></td><td>allow code reuse by multiple switch cases</td></tr> - <tr><td><code>G_GNUC_NO_INLINE</code></td><td>the function is mocked in the test suite</td></tr> - <tr><td><code>G_GNUC_NORETURN</code></td><td>the function never returns</td></tr> - <tr><td><code>G_GNUC_NULL_TERMINATED</code></td><td>last parameter must be NULL</td></tr> - <tr><td><code>G_GNUC_PRINTF</code></td><td>validate that the formatting string matches parameters</td></tr> - <tr><td><code>G_GNUC_UNUSED</code></td><td>parameter is unused in this implementation of the function</td></tr> - <tr><td><code>G_GNUC_WARN_UNUSED_RESULT</code></td><td>the return value must be checked</td></tr> - </table> - - <h2><a id="glib">Adoption of GLib APIs</a></h2> - - <p> - Libvirt has adopted use of the - <a href="https://developer.gnome.org/glib/stable/">GLib library</a>. - Due to libvirt's long history of development, there are many APIs - in libvirt, for which GLib provides an alternative solution. The - general rule to follow is that the standard GLib solution will be - preferred over historical libvirt APIs. Existing code will be - ported over to use GLib APIs over time, but new code should use - the GLib APIs straight away where possible. - </p> - - <p> - The following is a list of libvirt APIs that should no longer be - used in new code, and their suggested GLib replacements: - </p> - - <dl> - <dt><code>VIR_ALLOC</code>, <code>VIR_REALLOC</code>, - <code>VIR_RESIZE_N</code>, <code>VIR_EXPAND_N</code>, - <code>VIR_SHRINK_N</code>, <code>VIR_FREE</code>, - <code>VIR_APPEND_ELEMENT</code>, <code>VIR_INSERT_ELEMENT</code>, - <code>VIR_DELETE_ELEMENT</code></dt> - <dd>Prefer the GLib APIs <code>g_new0</code>/<code>g_renew</code>/ - <code>g_free</code> in most cases. There should rarely be a need - to use <code>g_malloc</code>/<code>g_realloc</code>. - Instead of using plain C arrays, it is preferrable to use - one of the GLib types, <code>GArray</code>, <code>GPtrArray</code> - or <code>GByteArray</code>. These - all use a struct to track the array memory and size together - and efficiently resize. <strong>NEVER MIX</strong> use of the - classic libvirt memory allocation APIs and GLib APIs within - a single method. Keep the style consistent, converting existing - code to GLib style in a separate, prior commit.</dd> - - <dt><code>virStrerror</code></dt> - <dd>The GLib <code>g_strerror()</code> function should be used instead, - which has a simpler calling convention as an added benefit.</dd> - - <table class="top_table"> - <tr><th>deprecated version</th><th>GLib version</th><th>Notes</th></tr> - <tr><td><code>VIR_ALLOC(var)</code></td><td><code>g_new0(var_t, 1)</code></td> - <td>the type needs to be passed explicitly</td></tr> - <tr><td><code>VIR_ALLOC_N</code></td><td><code>g_new0(var_t, n)</code></td><td></td></tr> - <tr><td><code>VIR_REALLOC_N</code></td><td><code>g_renew(var_t, ptr, n)</code></td> - <td>the newly added memory is not zeroed</td></tr> - <tr><td><code>VIR_EXPAND_N</code></td><td><code>g_renew(var_t, ptr, n)</code></td> - <td>zero the new memory manually or use an array type</td></tr> - <tr><td><code>VIR_SHRINK_N</code></td><td><code>g_renew(var_t, ptr, n)</code></td> - <td></td></tr> - <tr><td><code>VIR_APPEND_ELEMENT</code></td><td><code>g_array_append_val</code></td> - <td><code>g_ptr_array_add</code> or <code>g_byte_array_append</code></td></tr> - <tr><td><code>VIR_INSERT_ELEMENT</code></td><td><code>g_array_insert_val</code></td> - <td><code>g_ptr_array_insert</code></td></tr> - <tr><td><code>VIR_DELETE_ELEMENT</code></td><td><code>g_array_remove_index</code></td> - <td><code>g_ptr_array_remove_index</code> or <code>g_byte_array_remove_index</code></td></tr> - <tr><td><code>VIR_FREE</code></td><td><code>g_free</code></td> - <td><code>g_free</code> does not zero the pointer</td></tr> - </table> - - <p>String allocation macros and functions:</p> - <table class="top_table"> - <tr><th>deprecated version</th><th>GLib version</th><th>Notes</th></tr> - <tr><td><code>virAsprintf</code></td><td><code>g_strdup_printf</code></td><td></td></tr> - <tr><td><code>virVasprintf</code></td><td><code>g_strdup_vprint</code></td> - <td>use <code>g_vasprintf</code> if you really need to know the returned length</td></tr> - </table> - </dl> - - <p> - The following libvirt APIs have been deleted already: - </p> - <dl> - <dt><code>VIR_AUTOPTR</code>, <code>VIR_AUTOCLEAN</code>, <code>VIR_AUTOFREE</code></dt> - <dd>The GLib macros <code>g_autoptr</code>, <code>g_auto</code> and - <code>g_autofree</code> must be used - instead in all new code. In existing code, the GLib macros must - never be mixed with libvirt macros within a method, nor should - they be mixed with <code>VIR_FREE</code>. If introducing GLib macros to an - existing method, any use of libvirt macros must be converted - in an independent commit. - </dd> - - <dt><code>VIR_DEFINE_AUTOPTR_FUNC</code>, <code>VIR_DEFINE_AUTOCLEAN_FUNC</code></dt> - <dd>The GLib macros <code>G_DEFINE_AUTOPTR_CLEANUP_FUNC</code> and - <code>G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC</code> must be used in all - new code. Existing code should be converted to the - new macros where relevant. It is permissible to use - <code>g_autoptr</code>, <code>g_auto</code> on an object whose cleanup function - is declared with the libvirt macros and vice-versa. - </dd> - - <dt><code>VIR_AUTOUNREF</code></dt> - <dd>The GLib macros <code>g_autoptr</code> and <code>G_DEFINE_AUTOPTR_CLEANUP_FUNC</code> - should be used to manage autoclean of virObject classes. - This matches usage with GObject classes.</dd> - - <dt><code>VIR_STRDUP</code>, <code>VIR_STRNDUP</code></dt> - <dd>Prefer the GLib APIs <code>g_strdup</code> and <code>g_strndup</code>.</dd> - </dl> - <table class="top_table"> - <tr><th>deleted version</th><th>GLib version</th><th>Notes</th></tr> - <tr><td><code>VIR_AUTOPTR</code></td><td><code>g_autoptr</code></td><td></td></tr> - <tr><td><code>VIR_AUTOCLEAN</code></td><td><code>g_auto</code></td><td></td></tr> - <tr><td><code>VIR_AUTOFREE</code></td><td><code>g_autofree</code></td><td>The GLib version does not use parentheses</td></tr> - <tr><td><code>VIR_AUTOUNREF</code></td><td><code>g_autoptr</code></td><td>The cleanup function needs to be defined</td></tr> - <tr><td><code>VIR_DEFINE_AUTOPTR_FUNC</code></td><td><code>G_DEFINE_AUTOPTR_CLEANUP_FUNC</code></td><td></td></tr> - <tr><td><code>VIR_DEFINE_AUTOCLEAN_FUNC</code></td><td><code>G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC</code></td><td></td></tr> - <tr><td><code>VIR_STEAL_PTR</code></td><td><code>g_steal_pointer</code></td> - <td><code>a = f(&b)</code> instead of <code>f(a, b)</code></td></tr> - <tr><td><code>VIR_RETURN_PTR</code></td><td><code>return g_steal_pointer</code></td><td></td></tr> - <tr><td><code>ARRAY_CARDINALITY</code></td><td><code>G_N_ELEMENTS</code></td><td></td></tr> - <tr><td><code>ATTRIBUTE_FALLTHROUGH</code></td><td><code>G_GNUC_FALLTHROUGH</code></td><td></td></tr> - <tr><td><code>ATTRIBUTE_FMT_PRINTF</code></td><td><code>G_GNUC_PRINTF</code></td><td></td></tr> - <tr><td><code>ATTRIBUTE_NOINLINE</code></td><td><code>G_GNUC_NO_INLINE</code></td><td></td></tr> - <tr><td><code>ATTRIBUTE_NORETURN</code></td><td><code>G_GNUC_NORETURN</code></td><td></td></tr> - <tr><td><code>ATTRIBUTE_RETURN_CHECK</code></td><td><code>G_GNUC_WARN_UNUSED_RESULT</code></td><td></td></tr> - <tr><td><code>ATTRIBUTE_SENTINEL</code></td><td><code>G_GNUC_NULL_TERMINATED</code></td><td></td></tr> - <tr><td><code>ATTRIBUTE_UNUSED</code></td><td><code>G_GNUC_UNUSED</code></td><td></td></tr> - <tr><td><code>VIR_STRDUP</code></td><td><code>g_strdup</code></td><td></td></tr> - <tr><td><code>VIR_STRNDUP</code></td><td><code>g_strndup</code></td><td></td></tr> - <tr><td><code>virStrerror</code></td><td><code>g_strerror</code></td><td></td></tr> - </table> - - - <h2><a id="file_handling">File handling</a></h2> - - <p> - Usage of the <code>fdopen()</code>, <code>close()</code>, <code>fclose()</code> - APIs is deprecated in libvirt code base to help avoiding double-closing of files - or file descriptors, which is particularly dangerous in a multi-threaded - application. Instead of these APIs, use the macros from virfile.h - </p> - - <ul> - <li><p>Open a file from a file descriptor:</p> - -<pre> - if ((file = VIR_FDOPEN(fd, "r")) == NULL) { - virReportSystemError(errno, "%s", - _("failed to open file from file descriptor")); - return -1; - } - /* fd is now invalid; only access the file using file variable */ -</pre></li> - - <li><p>Close a file descriptor:</p> -<pre> - if (VIR_CLOSE(fd) < 0) { - virReportSystemError(errno, "%s", _("failed to close file")); - } -</pre></li> - - <li><p>Close a file:</p> - -<pre> - if (VIR_FCLOSE(file) < 0) { - virReportSystemError(errno, "%s", _("failed to close file")); - } -</pre></li> - - <li><p>Close a file or file descriptor in an error path, without losing - the previous <code>errno</code> value:</p> - -<pre> - VIR_FORCE_CLOSE(fd); - VIR_FORCE_FCLOSE(file); -</pre> - </li> - </ul> - - <h2><a id="string_comparision">String comparisons</a></h2> - - <p> - Do not use the strcmp, strncmp, etc functions directly. Instead use - one of the following semantically named macros - </p> - - <ul> - <li><p>For strict equality:</p> -<pre> - STREQ(a,b) - STRNEQ(a,b) -</pre> - </li> - - <li><p>For case insensitive equality:</p> -<pre> - STRCASEEQ(a,b) - STRCASENEQ(a,b) -</pre> - </li> - - <li><p>For strict equality of a substring:</p> -<pre> - STREQLEN(a,b,n) - STRNEQLEN(a,b,n) -</pre> - </li> - - <li><p>For case insensitive equality of a substring:</p> -<pre> - STRCASEEQLEN(a,b,n) - STRCASENEQLEN(a,b,n) -</pre> - </li> - - <li><p>For strict equality of a prefix:</p> -<pre> - STRPREFIX(a,b) -</pre> - </li> - <li><p>To avoid having to check if a or b are NULL:</p> -<pre> - STREQ_NULLABLE(a, b) - STRNEQ_NULLABLE(a, b) -</pre> - </li> - </ul> - - - <h2><a id="string_copying">String copying</a></h2> - - <p> - Do not use the strncpy function. According to the man page, it - does <b>not</b> guarantee a NULL-terminated buffer, which makes - it extremely dangerous to use. Instead, use one of the replacement - functions provided by libvirt: - </p> - -<pre> - virStrncpy(char *dest, const char *src, size_t n, size_t destbytes) -</pre> - <p> - The first two arguments have the same meaning as for strncpy, - namely the destination and source of the copy operation. Unlike - strncpy, the function will always copy exactly the number of bytes - requested and make sure the destination is NULL-terminated, as the - source is required to be; sanity checks are performed to ensure the - size of the destination, as specified by the last argument, is - sufficient for the operation to succeed. On success, 0 is returned; - on failure, a value <0 is returned instead. - </p> - -<pre> - virStrcpy(char *dest, const char *src, size_t destbytes) -</pre> - <p> - Use this variant if you know you want to copy the entire src - string into dest. - </p> - -<pre> - virStrcpyStatic(char *dest, const char *src) -</pre> - <p> - Use this variant if you know you want to copy the entire src - string into dest <b>and</b> you know that your destination string is - a static string (i.e. that sizeof(dest) returns something - meaningful). Note that this is a macro, so arguments could be - evaluated more than once. - </p> - -<pre> - dst = g_strdup(src); - dst = g_strndup(src, n); -</pre> - <p> - You should avoid using strdup or strndup directly as they do not handle - out-of-memory errors, and do not allow a NULL source. - Use <code>g_strdup</code> and <code>g_strndup</code> from GLib which - abort on OOM and handle NULL source by returning NULL. - </p> - - <h2><a id="strbuf">Variable length string buffer</a></h2> - - <p> - If there is a need for complex string concatenations, avoid using - the usual sequence of malloc/strcpy/strcat/snprintf functions and - make use of either the - <a href="https://developer.gnome.org/glib/stable/glib-Strings.html">GString</a> - type from GLib or the virBuffer API. - If formatting XML or QEMU command line is needed, use the virBuffer - API described in virbuffer.h, since it has helper functions for those. - </p> - - <p>Typical usage is as follows:</p> - -<pre> - char * - somefunction(...) - { - g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER; - - ... - - virBufferAddLit(&buf, "<domain>\n"); - virBufferAsprintf(&buf, " <memory>%d</memory>\n", memory); - if (some_error) - return NULL; /* g_auto will free the memory used so far */ - ... - virBufferAddLit(&buf, "</domain>\n"); - - ... - - if (virBufferCheckError(&buf) < 0) - return NULL; - - return virBufferContentAndReset(&buf); - } -</pre> - - - <h2><a id="includes">Include files</a></h2> - - <p> - There are now quite a large number of include files, both libvirt - internal and external, and system includes. To manage all this - complexity it's best to stick to the following general plan for all - *.c source files: - </p> - -<pre> - /* - * Copyright notice - * .... - * .... - * .... - * - */ - - #include <config.h> Must come first in every file. - - #include <stdio.h> Any system includes you need. - #include <string.h> - #include <limits.h> - - #if WITH_NUMACTL Some system includes aren't supported - # include <numa.h> everywhere so need these #if guards. - #endif - - #include "internal.h" Include this first, after system includes. - - #include "util.h" Any libvirt internal header files. - #include "buf.h" - - static int - myInternalFunc() The actual code. - { - ... -</pre> - - <p> - Of particular note: <b>Do not</b> include libvirt/libvirt.h, - libvirt/virterror.h, libvirt/libvirt-qemu.h, or libvirt/libvirt-lxc.h. - They are included by "internal.h" already and there are some special reasons - why you cannot include these files explicitly. One of the special cases, - "libvirt/libvirt.h" is included prior to "internal.h" in "remote_protocol.x", - to avoid exposing *_LAST enum elements. - </p> - - - <h2><a id="printf">Printf-style functions</a></h2> - - <p> - Whenever you add a new printf-style function, i.e., one with a format - string argument and following "..." in its prototype, be sure to use - gcc's printf attribute directive in the prototype. For example, here's - the one for virCommandAddEnvFormat in vircommand.h: - </p> - -<pre> - void virCommandAddEnvFormat(virCommandPtr cmd, const char *format, ...) - G_GNUC_PRINTF(2, 3); -</pre> - - <p> - This makes it so gcc's -Wformat and -Wformat-security options can do - their jobs and cross-check format strings with the number and types - of arguments. - </p> - - <p> - When printing to a string, consider using GString or virBuffer for - incremental allocations, g_strdup_printf for a one-shot allocation, - and g_snprintf for fixed-width buffers. Only use g_sprintf, - if you can prove the buffer won't overflow. - </p> - - <h2><a id="errors">Error message format</a></h2> - - <p> - Error messages visible to the user should be short and descriptive. All - error messages are translated using gettext and thus must be wrapped in - <code>_()</code> macro. To simplify the translation work, the error message - must not be concatenated from various parts. To simplify searching for - the error message in the code the strings should not be broken even - if they result into a line longer than 80 columns and any formatting - modifier should be enclosed by quotes or other obvious separator. - If a string used with <code>%s</code> can be NULL the NULLSTR macro must - be used. - </p> - -<pre> - GOOD: virReportError(VIR_ERR_INTERNAL_ERROR, - _("Failed to connect to remote host '%s'"), hostname) - - BAD: virReportError(VIR_ERR_INTERNAL_ERROR, - _("Failed to %s to remote host '%s'"), - "connect", hostname); - - BAD: virReportError(VIR_ERR_INTERNAL_ERROR, - _("Failed to connect " - "to remote host '%s'), - hostname); -</pre> - - <h2><a id="goto">Use of goto</a></h2> - - <p> - The use of goto is not forbidden, and goto is widely used - throughout libvirt. While the uncontrolled use of goto will - quickly lead to unmaintainable code, there is a place for it in - well structured code where its use increases readability and - maintainability. In general, if goto is used for error - recovery, it's likely to be ok, otherwise, be cautious or avoid - it all together. - </p> - - <p> - The typical use of goto is to jump to cleanup code in the case - of a long list of actions, any of which may fail and cause the - entire operation to fail. In this case, a function will have a - single label at the end of the function. It's almost always ok - to use this style. In particular, if the cleanup code only - involves free'ing memory, then having multiple labels is - overkill. g_free() and most of the functions named XXXFree() in - libvirt is required to handle NULL as its arg. This does not - apply to libvirt's public APIs. Thus you can - safely call free on all the variables even if they were not yet - allocated (yes they have to have been initialized to NULL). - This is much simpler and clearer than having multiple labels. - Note that most of libvirt's type declarations can be marked with - either <code>g_autofree</code> or <code>g_autoptr</code> which uses - the compiler's <code>__attribute__((cleanup))</code> that calls - the appropriate free function when the variable goes out of scope. - </p> - - <p> - There are a couple of signs that a particular use of goto is not - ok: - </p> - - <ul> - <li>You're using multiple labels. If you find yourself using - multiple labels, you're strongly encouraged to rework your code - to eliminate all but one of them.</li> - <li>The goto jumps back up to a point above the current line of - code being executed. Please use some combination of looping - constructs to re-execute code instead; it's almost certainly - going to be more understandable by others. One well-known - exception to this rule is restarting an i/o operation following - EINTR.</li> - <li>The goto jumps down to an arbitrary place in the middle of a - function followed by further potentially failing calls. You - should almost certainly be using a conditional and a block - instead of a goto. Perhaps some of your function's logic would - be better pulled out into a helper function.</li> - </ul> - - <p> - Although libvirt does not encourage the Linux kernel wind/unwind - style of multiple labels, there's a good general discussion of - the issue archived at - <a href="http://kerneltrap.org/node/553/2131">KernelTrap</a> - </p> - - <p> - When using goto, please use one of these standard labels if it - makes sense: - </p> - -<pre> - error: A path only taken upon return with an error code - cleanup: A path taken upon return with success code + optional error - no_memory: A path only taken upon return with an OOM error code - retry: If needing to jump upwards (e.g., retry on EINTR) -</pre> - - <p> - Top-level labels should be indented by one space (putting them on - the beginning of the line confuses function context detection in git): - </p> - -<pre> -int foo() -{ - /* ... do stuff ... */ - cleanup: - /* ... do other stuff ... */ -} -</pre> - - - - <h2><a id="committers">Libvirt committer guidelines</a></h2> - - <p> - The AUTHORS files indicates the list of people with commit access right - who can actually merge the patches. - </p> - - <p> - The general rule for committing a patch is to make sure - it has been reviewed - properly in the mailing-list first, usually if a couple of people gave an - ACK or +1 to a patch and nobody raised an objection on the list it should - be good to go. If the patch touches a part of the code where you're not - the main maintainer, or where you do not have a very clear idea of - how things work, it's better - to wait for a more authoritative feedback though. Before committing, please - also rebuild locally, run 'make check syntax-check', and make sure you - don't raise errors. - </p> - - <p> - An exception to 'review and approval on the list first' is fixing failures - to build: - </p> - <ul> - <li>if a recently committed patch breaks compilation on a platform - or for a given driver, then it's fine to commit a minimal fix - directly without getting the review feedback first</li> - <li>if make check or make syntax-check breaks, if there is - an obvious fix, it's fine to commit immediately. - The patch should still be sent to the list (or tell what the fix was if - trivial), and 'make check syntax-check' should pass too, before committing - anything</li> - <li> - fixes for documentation and code comments can be managed - in the same way, but still make sure they get reviewed if non-trivial. - </li> - <li>(ir)regular pulls from other repositories or automated updates, such - as the keycodemap submodule updates, pulling in new translations or updating - the container images for the CI system - </li> - </ul> - </body> -</html> diff --git a/docs/hacking.rst b/docs/hacking.rst new file mode 100644 index 0000000000..ac02e9ab73 --- /dev/null +++ b/docs/hacking.rst @@ -0,0 +1,1400 @@ +====================== +Contributor guidelines +====================== + +.. contents:: + +General tips for contributing patches +===================================== + +#. Discuss any large changes on the mailing list first. Post + patches early and listen to feedback. + +#. Official upstream repository is kept in git + (``https://libvirt.org/git/libvirt.git``) and is browsable + along with other libvirt-related repositories (e.g. + libvirt-python) `online <https://libvirt.org/git/>`__. + +#. Patches to translations are maintained via the `zanata + project <https://fedora.zanata.org/>`__. If you want to fix a + translation in a .po file, join the appropriate language team. + The libvirt release process automatically pulls the latest + version of each translation file from zanata. + +#. The simplest way to send patches is to use the + `git-publish <https://github.com/stefanha/git-publish>`__ + tool. All libvirt-related repositories contain a config file + that tells git-publish to use the correct mailing list and + subject prefix. + + Alternatively, you may send patches using ``git send-email``. + + Also, for code motion patches, you may find that + ``git diff --patience`` provides an easier-to-read + patch. However, the usual workflow of libvirt developer is: + + :: + + git checkout master + git pull + git checkout -t origin -b workbranch + Hack, committing any changes along the way + + More hints on compiling can be found `here <compiling.html>`__. + When you want to post your patches: + + :: + + git pull --rebase + (fix any conflicts) + git send-email --cover-letter --no-chain-reply-to --annotate \ + --confirm=always --to=libvir-list@redhat.com master + + For a single patch you can omit ``--cover-letter``, but a + series of two or more patches needs a cover letter. + + Note that the ``git send-email`` subcommand may not be in the + main git package and using it may require installation of a + separate package, for example the "git-email" package in Fedora + and Debian. If this is your first time using + ``git send-email``, you might need to configure it to point it + to your SMTP server with something like: + + :: + + git config --global sendemail.smtpServer stmp.youremailprovider.net + + If you get tired of typing ``--to=libvir-list@redhat.com`` all + the time, you can configure that to be automatically handled as + well: + + :: + + git config sendemail.to libvir-list@redhat.com + + As a rule, patches should be sent to the mailing list only: all + developers are subscribed to libvir-list and read it regularly, + so **please don't CC individual developers** unless they've + explicitly asked you to. + + Avoid using mail clients for sending patches, as most of them + will mangle the messages in some way, making them unusable for + our purposes. Gmail and other Web-based mail clients are + particularly bad at this. + + If everything went well, your patch should show up on the + `libvir-list + archives <https://www.redhat.com/archives/libvir-list/>`__ in a + matter of minutes; if you still can't find it on there after an + hour or so, you should double-check your setup. **Note that, if + you are not already a subscriber, your very first post to the + mailing list will be subject to moderation**, and it's not + uncommon for that to take around a day. + + Please follow this as close as you can, especially the rebase + and ``git send-email`` part, as it makes life easier for other + developers to review your patch set. + + One should avoid sending patches as attachments, but rather + send them in email body along with commit message. If a + developer is sending another version of the patch (e.g. to + address review comments), they are advised to note differences + to previous versions after the ``---`` line in the patch so + that it helps reviewers but doesn't become part of git history. + Moreover, such patch needs to be prefixed correctly with + ``--subject-prefix=PATCHv2`` appended to + ``git send-email`` (substitute ``v2`` with the + correct version if needed though). + +#. In your commit message, make the summary line reasonably short + (60 characters is typical), followed by a blank line, followed + by any longer description of why your patch makes sense. If the + patch fixes a regression, and you know what commit introduced + the problem, mentioning that is useful. If the patch resolves a + bugzilla report, mentioning the URL of the bug number is + useful; but also summarize the issue rather than making all + readers follow the link. You can use 'git shortlog -30' to get + an idea of typical summary lines. + +#. Contributors to libvirt projects **must** assert that they are + in compliance with the `Developer Certificate of Origin + 1.1 <https://developercertificate.org/>`__. This is achieved by + adding a "Signed-off-by" line containing the contributor's name + and e-mail to every commit message. The presence of this line + attests that the contributor has read the above lined DCO and + agrees with its statements. + +#. Split large changes into a series of smaller patches, + self-contained if possible, with an explanation of each patch + and an explanation of how the sequence of patches fits + together. Moreover, please keep in mind that it's required to + be able to compile cleanly (**including** + ``make check`` and ``make syntax-check``) after each + patch. A feature does not have to work until the end of a + series, but intermediate patches must compile and not cause + test-suite failures (this is to preserve the usefulness of + ``git bisect``, among other things). + +#. Make sure your patches apply against libvirt GIT. Developers + only follow GIT and don't care much about released versions. + +#. Run the automated tests on your code before submitting any + changes. That is: + + :: + + make check + make syntax-check + make -C tests valgrind + + `Valgrind <http://valgrind.org/>`__ is a test that checks for + memory management issues, such as leaks or use of uninitialized + variables. + + Some tests are skipped by default in a development environment, + based on the time they take in comparison to the likelihood + that those tests will turn up problems during incremental + builds. These tests default to being run when building from a + tarball or with the configure option --enable-expensive-tests; + you can also force a one-time toggle of these tests by setting + VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in: + + :: + + make check VIR_TEST_EXPENSIVE=1 + + If you encounter any failing tests, the VIR_TEST_DEBUG + environment variable may provide extra information to debug the + failures. Larger values of VIR_TEST_DEBUG may provide larger + amounts of information: + + :: + + VIR_TEST_DEBUG=1 make check (or) + VIR_TEST_DEBUG=2 make check + + When debugging failures during development, it is possible to + focus in on just the failing subtests by using VIR_TEST_RANGE. + I.e. to run all tests from 3 to 20 with the exception of tests + 6 and 16, use: + + :: + + VIR_TEST_DEBUG=1 VIR_TEST_RANGE=3-5,7-20,^16 ./run tests/qemuxml2argvtest + + Also, individual tests can be run from inside the ``tests/`` + directory, like: + + :: + + ./qemuxml2xmltest + + If you are adding new test cases, or making changes that alter + existing test output, you can use the environment variable + VIR_TEST_REGENERATE_OUTPUT to quickly update the saved test + data. Of course you still need to review the changes VERY + CAREFULLY to ensure they are correct. + + :: + + VIR_TEST_REGENERATE_OUTPUT=1 ./qemuxml2argvtest + + There is also a ``./run`` script at the top level, to make it + easier to run programs that have not yet been installed, as + well as to wrap invocations of various tests under gdb or + Valgrind. + + When running our test suite it may happen that the test result + is nondeterministic because of the test suite relying on a + particular file in the system being accessible or having some + specific value. To catch this kind of errors, the test suite + has a module for that prints any path touched that fulfils + constraints described above into a file. To enable it just set + ``VIR_TEST_FILE_ACCESS`` environment variable. Then + ``VIR_TEST_FILE_ACCESS_OUTPUT`` environment variable can alter + location where the file is stored. + + :: + + VIR_TEST_FILE_ACCESS=1 VIR_TEST_FILE_ACCESS_OUTPUT="/tmp/file_access.txt" ./qemuxml2argvtest + +#. The Valgrind test should produce similar output to + ``make check``. If the output has traces within libvirt API's, + then investigation is required in order to determine the cause + of the issue. Output such as the following indicates some sort + of leak: + + :: + + ==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89 + ==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270) + ==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8) + ==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410) + ==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188) + ==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640) + ==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590) + ==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100) + ==5414== by 0x41E20F: virtTestRun (testutils.c:161) + ==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866) + ==5414== by 0x41E84A: virtTestMain (testutils.c:723) + ==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so) + + In this example, the ``virDomainDefParseXML()`` had an error + path where the ``virDomainVideoDefPtr video`` pointer was not + properly disposed. By simply adding a + ``virDomainVideoDefFree(video);`` in the error path, the issue + was resolved. + + Another common mistake is calling a printing function, such as + ``VIR_DEBUG()`` without initializing a variable to be printed. + The following example involved a call which could return an + error, but not set variables passed by reference to the call. + The solution was to initialize the variables prior to the call. + + :: + + ==4749== Use of uninitialised value of size 8 + ==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so) + ==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so) + ==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so) + ==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199) + ==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814) + ==4749== by 0x4C8AA96: virLogMessage (virlog.c:751) + ==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225) + ==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439) + ==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562) + ==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927) + ==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467) + ==4749== by 0x40AB8F: virtTestRun (testutils.c:161) + + Valgrind will also find some false positives or code paths + which cannot be resolved by making changes to the libvirt code. + For these paths, it is possible to add a filter to avoid the + errors. For example: + + :: + + ==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20 + ==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270) + ==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so) + ==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1) + ==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1) + ==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so) + ==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so) + ==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so) + + In this instance, it is acceptable to modify the + ``tests/.valgrind.supp`` file in order to add a suppression + filter. The filter should be unique enough to not suppress real + leaks, but it should be generic enough to cover multiple code + paths. The format of the entry can be found in the + documentation found at the `Valgrind home + page <http://valgrind.org/>`__. The following trace was added + to ``tests/.valgrind.supp`` in order to suppress the warning: + + :: + + { + dlInitMemoryLeak1 + Memcheck:Leak + fun:?alloc + ... + fun:call_init.part.0 + fun:_dl_init + ... + obj:*/lib*/ld-2.*so* + } + +#. Update tests and/or documentation, particularly if you are + adding a new feature or changing the output of a program. + +#. Don't forget to update the `release notes <news.html>`__ by + changing ``docs/news.xml`` if your changes are significant. All + user-visible changes, such as adding new XML elements or fixing + all but the most obscure bugs, must be (briefly) described in a + release notes entry; changes that are only relevant to other + libvirt developers, such as code refactoring, don't belong in + the release notes. Note that ``docs/news.xml`` should be + updated in its own commit not to get in the way of backports. + +There is more on this subject, including lots of links to +background reading on the subject, on `Richard Jones' guide to +working with open source +projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. + +Language Usage +============== + +The libvirt repository makes use of a large number of programming +languages. It is anticipated that in the future libvirt will adopt +use of other new languages. To reduce the overall burden on +developers, there is thus a general desire to phase out usage of +some of the existing languages. + +The preferred languages at this time are: + +- C - for the main libvirt codebase. Dialect supported by + GCC/CLang only. +- Python - for supporting build scripts / tools. Code must run + with both version 2.7 and 3.x at this time. + +Languages that should not be used for any new contributions: + +- Perl - build scripts must be written in Python instead. +- Shell - build scripts must be written in Python instead. + +Tooling +======= + +libvirt includes support for some useful development tools right +in its source repository, meaning users will be able to take +advantage of them without little or no configuration. Examples +include: + +- `color_coded <https://github.com/jeaye/color_coded>`__, a vim + plugin for libclang-powered semantic syntax highlighting; +- `YouCompleteMe <http://valloric.github.io/YouCompleteMe/>`__, a + vim plugin for libclang-powered semantic code completion. + +Naming conventions +================== + +When reading libvirt code, a number of different naming +conventions will be evident due to various changes in thinking +over the course of the project's lifetime. The conventions +documented below should be followed when creating any entirely new +files in libvirt. When working on existing files, while it is +desirable to apply these conventions, keeping a consistent style +with existing code in that particular file is generally more +important. The overall guiding principal is that every file, enum, +struct, function, macro and typedef name must have a 'vir' or +'VIR' prefix. All local scope variable names are exempt, and +global variables are exempt, unless exported in a header file. + +File names + File naming varies depending on the subdirectory. The preferred + style is to have a 'vir' prefix, followed by a name which + matches the name of the functions / objects inside the file. + For example, a file containing an object 'virHashtable' is + stored in files 'virhashtable.c' and 'virhashtable.h'. + Sometimes, methods which would otherwise be declared 'static' + need to be exported for use by a test suite. For this purpose a + second header file should be added with a suffix of 'priv', + e.g. 'virhashtablepriv.h'. Use of underscores in file names is + discouraged when using the 'vir' prefix style. The 'vir' prefix + naming applies to src/util, src/rpc and tests/ directories. + Most other directories do not follow this convention. + +Enum type & field names + All enums should have a 'vir' prefix in their typedef name, and + each following word should have its first letter in uppercase. + The enum name should match the typedef name with a leading + underscore. The enum member names should be in all uppercase, + and use an underscore to separate each word. The enum member + name prefix should match the enum typedef name. + + :: + + typedef enum _virSocketType virSocketType; + enum _virSocketType { + VIR_SOCKET_TYPE_IPV4, + VIR_SOCKET_TYPE_IPV6, + }; + +Struct type names + All structs should have a 'vir' prefix in their typedef name, + and each following word should have its first letter in + uppercase. The struct name should be the same as the typedef + name with a leading underscore. A second typedef should be + given for a pointer to the struct with a 'Ptr' suffix. + + :: + + typedef struct _virHashTable virHashTable; + typedef virHashTable *virHashTablePtr; + struct _virHashTable { + ... + }; + +Function names + All functions should have a 'vir' prefix in their name, + followed by one or more words with first letter of each word + capitalized. Underscores should not be used in function names. + If the function is operating on an object, then the function + name prefix should match the object typedef name, otherwise it + should match the filename. Following this comes the verb / + action name, and finally an optional subject name. For example, + given an object 'virHashTable', all functions should have a + name 'virHashTable$VERB' or 'virHashTable$VERB$SUBJECT", e.g. + 'virHashTableLookup' or 'virHashTableGetValue'. + +Macro names + All macros should have a "VIR" prefix in their name, followed + by one or more uppercase words separated by underscores. The + macro argument names should be in lowercase. Aside from having + a "VIR" prefix there are no common practices for the rest of + the macro name. + +Code indentation +================ + +Libvirt's C source code generally adheres to some basic +code-formatting conventions. The existing code base is not totally +consistent on this front, but we do prefer that contributed code +be formatted similarly. In short, use spaces-not-TABs for +indentation, use 4 spaces for each indentation level, and other +than that, follow the K&R style. + +If you use Emacs, the project includes a file .dir-locals.el that +sets up the preferred indentation. If you use vim, append the +following to your ~/.vimrc file: + +:: + + set nocompatible + filetype on + set autoindent + set smartindent + set cindent + set tabstop=8 + set shiftwidth=4 + set expandtab + set cinoptions=(0,:0,l1,t0,L3 + filetype plugin indent on + au FileType make setlocal noexpandtab + au BufRead,BufNewFile *.am setlocal noexpandtab + match ErrorMsg /\s\+$\| \+\ze\t/ + +Or if you don't want to mess your ~/.vimrc up, you can save the +above into a file called .lvimrc (not .vimrc) located at the root +of libvirt source, then install a vim script from +http://www.vim.org/scripts/script.php?script_id=1408, which will +load the .lvimrc only when you edit libvirt code. + +Code formatting (especially for new code) +========================================= + +With new code, we can be even more strict. Please apply the +following function (using GNU indent) to any new code. Note that +this also gives you an idea of the type of spacing we prefer +around operators and keywords: + +:: + + indent-libvirt() + { + indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \ + -sbi4 -psl -saf -sai -saw -sbi4 -ss -sc -cdw -cli4 -npcs -nbc \ + --no-tabs "$@" + } + +Note that sometimes you'll have to post-process that output +further, by piping it through ``expand -i``, since some leading +TABs can get through. Usually they're in macro definitions or +strings, and should be converted anyhow. + +Libvirt requires a C99 compiler for various reasons. However, most +of the code base prefers to stick to C89 syntax unless there is a +compelling reason otherwise. For example, it is preferable to use +``/* */`` comments rather than ``//``. Also, when declaring local +variables, the prevailing style has been to declare them at the +beginning of a scope, rather than immediately before use. + +Bracket spacing +--------------- + +The keywords ``if``, ``for``, ``while``, and ``switch`` must have +a single space following them before the opening bracket. E.g. + +:: + + if(foo) // Bad + if (foo) // Good + +Function implementations must **not** have any whitespace between +the function name and the opening bracket. E.g. + +:: + + int foo (int wizz) // Bad + int foo(int wizz) // Good + +Function calls must **not** have any whitespace between the +function name and the opening bracket. E.g. + +:: + + bar = foo (wizz); // Bad + bar = foo(wizz); // Good + +Function typedefs must **not** have any whitespace between the +closing bracket of the function name and opening bracket of the +arg list. E.g. + +:: + + typedef int (*foo) (int wizz); // Bad + typedef int (*foo)(int wizz); // Good + +There must not be any whitespace immediately following any opening +bracket, or immediately prior to any closing bracket. E.g. + +:: + + int foo( int wizz ); // Bad + int foo(int wizz); // Good + +Commas +------ + +Commas should always be followed by a space or end of line, and +never have leading space; this is enforced during 'make +syntax-check'. + +:: + + call(a,b ,c);// Bad + call(a, b, c); // Good + +When declaring an enum or using a struct initializer that occupies +more than one line, use a trailing comma. That way, future edits +to extend the list only have to add a line, rather than modify an +existing line to add the intermediate comma. Any sentinel +enumerator value with a name ending in \_LAST is exempt, since you +would extend such an enum before the \_LAST element. Another +reason to favor trailing commas is that it requires less effort to +produce via code generators. Note that the syntax checker is +unable to enforce a style of trailing commas, so there are +counterexamples in existing code which do not use it; also, while +C99 allows trailing commas, remember that JSON and XDR do not. + +:: + + enum { + VALUE_ONE, + VALUE_TWO // Bad + }; + enum { + VALUE_THREE, + VALUE_FOUR, // Good + }; + +Semicolons +---------- + +Semicolons should never have a space beforehand. Inside the +condition of a ``for`` loop, there should always be a space or +line break after each semicolon, except for the special case of an +infinite loop (although more infinite loops use ``while``). While +not enforced, loop counters generally use post-increment. + +:: + + for (i = 0 ;i < limit ; ++i) { // Bad + for (i = 0; i < limit; i++) { // Good + for (;;) { // ok + while (1) { // Better + +Empty loop bodies are better represented with curly braces and a +comment, although use of a semicolon is not currently rejected. + +:: + + while ((rc = waitpid(pid, &st, 0) == -1) && + errno == EINTR); // ok + while ((rc = waitpid(pid, &st, 0) == -1) && + errno == EINTR) { // Better + /* nothing */ + } + +Curly braces +------------ + +Omit the curly braces around an ``if``, ``while``, ``for`` etc. +body only when both that body and the condition itself occupy a +single line. In every other case we require the braces. This +ensures that it is trivially easy to identify a +single-\ *statement* loop: each has only one *line* in its body. + +:: + + while (expr) // single line body; {} is forbidden + single_line_stmt(); + +:: + + while (expr(arg1, + arg2)) // indentation makes it obvious it is single line, + single_line_stmt(); // {} is optional (not enforced either way) + +:: + + while (expr1 && + expr2) { // multi-line, at same indentation, {} required + single_line_stmt(); + } + +However, the moment your loop/if/else body extends on to a second +line, for whatever reason (even if it's just an added comment), +then you should add braces. Otherwise, it would be too easy to +insert a statement just before that comment (without adding +braces), thinking it is already a multi-statement loop: + +:: + + while (true) // BAD! multi-line body with no braces + /* comment... */ + single_line_stmt(); + +Do this instead: + +:: + + while (true) { // Always put braces around a multi-line body. + /* comment... */ + single_line_stmt(); + } + +There is one exception: when the second body line is not at the +same indentation level as the first body line: + +:: + + if (expr) + die("a diagnostic that would make this line" + " extend past the 80-column limit")); + +It is safe to omit the braces in the code above, since the +further-indented second body line makes it obvious that this is +still a single-statement body. + +To reiterate, don't do this: + +:: + + if (expr) // BAD: no braces around... + while (expr_2) { // ... a multi-line body + ... + } + +Do this, instead: + +:: + + if (expr) { + while (expr_2) { + ... + } + } + +However, there is one exception in the other direction, when even +a one-line block should have braces. That occurs when that +one-line, brace-less block is an ``if`` or ``else`` block, and the +counterpart block **does** use braces. In that case, put braces +around both blocks. Also, if the ``else`` block is much shorter +than the ``if`` block, consider negating the ``if``-condition and +swapping the bodies, putting the short block first and making the +longer, multi-line block be the ``else`` block. + +:: + + if (expr) { + ... + ... + } + else + x = y; // BAD: braceless "else" with braced "then", + // and short block last + + if (expr) + x = y; // BAD: braceless "if" with braced "else" + else { + ... + ... + } + +Keeping braces consistent and putting the short block first is +preferred, especially when the multi-line body is more than a few +lines long, because it is easier to read and grasp the semantics +of an if-then-else block when the simpler block occurs first, +rather than after the more involved block: + +:: + + if (!expr) { + x = y; // putting the smaller block first is more readable + } else { + ... + ... + } + +But if negating a complex condition is too ugly, then at least add +braces: + +:: + + if (complex expr not worth negating) { + ... + ... + } else { + x = y; + } + +Use hanging braces for compound statements: the opening brace of a +compound statement should be on the same line as the condition +being tested. Only top-level function bodies, nested scopes, and +compound structure declarations should ever have { on a line by +itself. + +:: + + void + foo(int a, int b) + { // correct - function body + int 2d[][] = { + { // correct - complex initialization + 1, 2, + }, + }; + if (a) + { // BAD: compound brace on its own line + do_stuff(); + } + { // correct - nested scope + int tmp; + if (a < b) { // correct - hanging brace + tmp = b; + b = a; + a = tmp; + } + } + } + +Conditional expressions +----------------------- + +For readability reasons new code should avoid shortening +comparisons to 0 for numeric types. Boolean and pointer +comparisions may be shortened. All long forms are okay: + +:: + + virFooPtr foos = NULL; + size nfoos = 0; + bool hasFoos = false; + + GOOD: + if (!foos) + if (!hasFoos) + if (nfoos == 0) + if (foos == NULL) + if (hasFoos == true) + + BAD: + if (!nfoos) + if (nfoos) + +New code should avoid the ternary operator as much as possible. +Specifically it must never span more than one line or nest: + +:: + + BAD: + char *foo = baz ? + virDoSomethingReallyComplex(driver, vm, something, baz->foo) : + NULL; + + char *foo = bar ? bar->baz ? bar->baz->foo : "nobaz" : "nobar"; + +Preprocessor +------------ + +Macros defined with an ALL_CAPS name should generally be assumed +to be unsafe with regards to arguments with side-effects (that is, +MAX(a++, b--) might increment a or decrement b too many or too few +times). Exceptions to this rule are explicitly documented for +macros in viralloc.h and virstring.h. + +For variadic macros, stick with C99 syntax: + +:: + + #define vshPrint(_ctl, ...) fprintf(stdout, __VA_ARGS__) + +Use parenthesis when checking if a macro is defined, and use +indentation to track nesting: + +:: + + #if defined(HAVE_POSIX_FALLOCATE) && !defined(HAVE_FALLOCATE) + # define fallocate(a, ignored, b, c) posix_fallocate(a, b, c) + #endif + +C types +------- + +Use the right type. + +Scalars +^^^^^^^ + +- If you're using ``int`` or ``long``, odds are good that there's + a better type. +- If a variable is counting something, be sure to declare it with + an unsigned type. +- If it's memory-size-related, use ``size_t`` (use ``ssize_t`` + only if required). +- If it's file-size related, use uintmax_t, or maybe ``off_t``. +- If it's file-offset related (i.e., signed), use ``off_t``. +- If it's just counting small numbers use ``unsigned int``; (on + all but oddball embedded systems, you can assume that that type + is at least four bytes wide). +- If a variable has boolean semantics, give it the ``bool`` type + and use the corresponding ``true`` and ``false`` macros. +- In the unusual event that you require a specific width, use a + standard type like ``int32_t``, ``uint32_t``, ``uint64_t``, + etc. +- While using ``bool`` is good for readability, it comes with + minor caveats: + + - Don't use ``bool`` in places where the type size must be + constant across all systems, like public interfaces and + on-the-wire protocols. Note that it would be possible + (albeit wasteful) to use ``bool`` in libvirt's logical wire + protocol, since XDR maps that to its lower-level ``bool_t`` + type, which **is** fixed-size. + - Don't compare a bool variable against the literal, ``true``, + since a value with a logical non-false value need not be + ``1``. I.e., don't write ``if (seen == true) ...``. Rather, + write ``if (seen)...``. + +Of course, take all of the above with a grain of salt. If you're +about to use some system interface that requires a type like +``size_t``, ``pid_t`` or ``off_t``, use matching types for any +corresponding variables. + +Also, if you try to use e.g., ``unsigned int`` as a type, and that +conflicts with the signedness of a related variable, sometimes +it's best just to use the **wrong** type, if *pulling the thread* +and fixing all related variables would be too invasive. + +Finally, while using descriptive types is important, be careful +not to go overboard. If whatever you're doing causes warnings, or +requires casts, then reconsider or ask for help. + +Pointers +^^^^^^^^ + +Ensure that all of your pointers are *const-correct*. Unless a +pointer is used to modify the pointed-to storage, give it the +``const`` attribute. That way, the reader knows up-front that this +is a read-only pointer. Perhaps more importantly, if we're +diligent about this, when you see a non-const pointer, you're +guaranteed that it is used to modify the storage it points to, or +it is aliased to another pointer that is. + +Attribute annotations +--------------------- + +Use the following annotations to help the compiler and/or static +analysis tools understand the code better: + ++-------------------------------+------------------------------------------------------------+ +| Macro | Meaning | ++===============================+============================================================+ +| ``ATTRIBUTE_NONNULL`` | passing NULL for this parameter is not allowed | ++-------------------------------+------------------------------------------------------------+ +| ``ATTRIBUTE_PACKED`` | force a structure to be packed | ++-------------------------------+------------------------------------------------------------+ +| ``G_GNUC_FALLTHROUGH`` | allow code reuse by multiple switch cases | ++-------------------------------+------------------------------------------------------------+ +| ``G_GNUC_NO_INLINE`` | the function is mocked in the test suite | ++-------------------------------+------------------------------------------------------------+ +| ``G_GNUC_NORETURN`` | the function never returns | ++-------------------------------+------------------------------------------------------------+ +| ``G_GNUC_NULL_TERMINATED`` | last parameter must be NULL | ++-------------------------------+------------------------------------------------------------+ +| ``G_GNUC_PRINTF`` | validate that the formatting string matches parameters | ++-------------------------------+------------------------------------------------------------+ +| ``G_GNUC_UNUSED`` | parameter is unused in this implementation of the function | ++-------------------------------+------------------------------------------------------------+ +| ``G_GNUC_WARN_UNUSED_RESULT`` | the return value must be checked | ++-------------------------------+------------------------------------------------------------+ + +Adoption of GLib APIs +--------------------- + +Libvirt has adopted use of the `GLib +library <https://developer.gnome.org/glib/stable/>`__. Due to +libvirt's long history of development, there are many APIs in +libvirt, for which GLib provides an alternative solution. The +general rule to follow is that the standard GLib solution will be +preferred over historical libvirt APIs. Existing code will be +ported over to use GLib APIs over time, but new code should use +the GLib APIs straight away where possible. + +The following is a list of libvirt APIs that should no longer be +used in new code, and their suggested GLib replacements: + +``VIR_ALLOC``, ``VIR_REALLOC``, ``VIR_RESIZE_N``, ``VIR_EXPAND_N``, ``VIR_SHRINK_N``, ``VIR_FREE``, ``VIR_APPEND_ELEMENT``, ``VIR_INSERT_ELEMENT``, ``VIR_DELETE_ELEMENT`` + Prefer the GLib APIs ``g_new0``/``g_renew``/ ``g_free`` in most + cases. There should rarely be a need to use + ``g_malloc``/``g_realloc``. Instead of using plain C arrays, it + is preferrable to use one of the GLib types, ``GArray``, + ``GPtrArray`` or ``GByteArray``. These all use a struct to + track the array memory and size together and efficiently + resize. **NEVER MIX** use of the classic libvirt memory + allocation APIs and GLib APIs within a single method. Keep the + style consistent, converting existing code to GLib style in a + separate, prior commit. +``virStrerror`` + The GLib ``g_strerror()`` function should be used instead, + which has a simpler calling convention as an added benefit. + +The following libvirt APIs have been deleted already: + +``VIR_AUTOPTR``, ``VIR_AUTOCLEAN``, ``VIR_AUTOFREE`` + The GLib macros ``g_autoptr``, ``g_auto`` and ``g_autofree`` + must be used instead in all new code. In existing code, the + GLib macros must never be mixed with libvirt macros within a + method, nor should they be mixed with ``VIR_FREE``. If + introducing GLib macros to an existing method, any use of + libvirt macros must be converted in an independent commit. +``VIR_DEFINE_AUTOPTR_FUNC``, ``VIR_DEFINE_AUTOCLEAN_FUNC`` + The GLib macros ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` and + ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` must be used in all new + code. Existing code should be converted to the new macros where + relevant. It is permissible to use ``g_autoptr``, ``g_auto`` on + an object whose cleanup function is declared with the libvirt + macros and vice-versa. +``VIR_AUTOUNREF`` + The GLib macros ``g_autoptr`` and + ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` should be used to manage + autoclean of virObject classes. This matches usage with GObject + classes. +``VIR_STRDUP``, ``VIR_STRNDUP`` + Prefer the GLib APIs ``g_strdup`` and ``g_strndup``. + ++-------------------------------+--------------------------------------+-------------------------------------------+ +| deleted version | GLib version | Notes | ++===============================+======================================+===========================================+ +| ``VIR_AUTOPTR`` | ``g_autoptr`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOCLEAN`` | ``g_auto`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOFREE`` | ``g_autofree`` | The GLib version does not use parentheses | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOUNREF`` | ``g_autoptr`` | The cleanup function needs to be defined | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_DEFINE_AUTOPTR_FUNC`` | ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_DEFINE_AUTOCLEAN_FUNC`` | ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STEAL_PTR`` | ``g_steal_pointer`` | ``a = f(&b)`` instead of ``f(a, b)`` | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_RETURN_PTR`` | ``return g_steal_pointer`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ARRAY_CARDINALITY`` | ``G_N_ELEMENTS`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_FALLTHROUGH`` | ``G_GNUC_FALLTHROUGH`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_FMT_PRINTF`` | ``G_GNUC_PRINTF`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_NOINLINE`` | ``G_GNUC_NO_INLINE`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_NORETURN`` | ``G_GNUC_NORETURN`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_RETURN_CHECK`` | ``G_GNUC_WARN_UNUSED_RESULT`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_SENTINEL`` | ``G_GNUC_NULL_TERMINATED`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_UNUSED`` | ``G_GNUC_UNUSED`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STRDUP`` | ``g_strdup`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STRNDUP`` | ``g_strndup`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``virStrerror`` | ``g_strerror`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ + +File handling +------------- + +Usage of the ``fdopen()``, ``close()``, ``fclose()`` APIs is +deprecated in libvirt code base to help avoiding double-closing of +files or file descriptors, which is particularly dangerous in a +multi-threaded application. Instead of these APIs, use the macros +from virfile.h + +- Open a file from a file descriptor: + + :: + + if ((file = VIR_FDOPEN(fd, "r")) == NULL) { + virReportSystemError(errno, "%s", + _("failed to open file from file descriptor")); + return -1; + } + /* fd is now invalid; only access the file using file variable */ + +- Close a file descriptor: + + :: + + if (VIR_CLOSE(fd) < 0) { + virReportSystemError(errno, "%s", _("failed to close file")); + } + +- Close a file: + + :: + + if (VIR_FCLOSE(file) < 0) { + virReportSystemError(errno, "%s", _("failed to close file")); + } + +- Close a file or file descriptor in an error path, without + losing the previous ``errno`` value: + + :: + + VIR_FORCE_CLOSE(fd); + VIR_FORCE_FCLOSE(file); + +String comparisons +------------------ + +Do not use the strcmp, strncmp, etc functions directly. Instead +use one of the following semantically named macros + +- For strict equality: + + :: + + STREQ(a,b) + STRNEQ(a,b) + +- For case insensitive equality: + + :: + + STRCASEEQ(a,b) + STRCASENEQ(a,b) + +- For strict equality of a substring: + + :: + + STREQLEN(a,b,n) + STRNEQLEN(a,b,n) + +- For case insensitive equality of a substring: + + :: + + STRCASEEQLEN(a,b,n) + STRCASENEQLEN(a,b,n) + +- For strict equality of a prefix: + + :: + + STRPREFIX(a,b) + +- To avoid having to check if a or b are NULL: + + :: + + STREQ_NULLABLE(a, b) + STRNEQ_NULLABLE(a, b) + +String copying +-------------- + +Do not use the strncpy function. According to the man page, it +does **not** guarantee a NULL-terminated buffer, which makes it +extremely dangerous to use. Instead, use one of the replacement +functions provided by libvirt: + +:: + + virStrncpy(char *dest, const char *src, size_t n, size_t destbytes) + +The first two arguments have the same meaning as for strncpy, +namely the destination and source of the copy operation. Unlike +strncpy, the function will always copy exactly the number of bytes +requested and make sure the destination is NULL-terminated, as the +source is required to be; sanity checks are performed to ensure +the size of the destination, as specified by the last argument, is +sufficient for the operation to succeed. On success, 0 is +returned; on failure, a value <0 is returned instead. + +:: + + virStrcpy(char *dest, const char *src, size_t destbytes) + +Use this variant if you know you want to copy the entire src +string into dest. + +:: + + virStrcpyStatic(char *dest, const char *src) + +Use this variant if you know you want to copy the entire src +string into dest **and** you know that your destination string is +a static string (i.e. that sizeof(dest) returns something +meaningful). Note that this is a macro, so arguments could be +evaluated more than once. + +:: + + dst = g_strdup(src); + dst = g_strndup(src, n); + +You should avoid using strdup or strndup directly as they do not +handle out-of-memory errors, and do not allow a NULL source. Use +``g_strdup`` and ``g_strndup`` from GLib which abort on OOM and +handle NULL source by returning NULL. + +Variable length string buffer +----------------------------- + +If there is a need for complex string concatenations, avoid using +the usual sequence of malloc/strcpy/strcat/snprintf functions and +make use of either the +`GString <https://developer.gnome.org/glib/stable/glib-Strings.html>`__ +type from GLib or the virBuffer API. If formatting XML or QEMU +command line is needed, use the virBuffer API described in +virbuffer.h, since it has helper functions for those. + +Typical usage is as follows: + +:: + + char * + somefunction(...) + { + g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER; + + ... + + virBufferAddLit(&buf, "<domain>\n"); + + ... + + if (some_error) + return NULL; /* g_auto will free the memory used so far */ + + ... + + virBufferAddLit(&buf, "</domain>\n"); + + ... + + if (virBufferCheckError(&buf) < 0) + return NULL; + + return virBufferContentAndReset(&buf); + } + +Include files +------------- + +There are now quite a large number of include files, both libvirt +internal and external, and system includes. To manage all this +complexity it's best to stick to the following general plan for +all \*.c source files: + +:: + + /* + * Copyright notice + * .... + * .... + * .... + * + */ + + #include <config.h> Must come first in every file. + + #include <stdio.h> Any system includes you need. + #include <string.h> + #include <limits.h> + + #if WITH_NUMACTL Some system includes aren't supported + # include <numa.h> everywhere so need these #if guards. + #endif + + #include "internal.h" Include this first, after system includes. + + #include "util.h" Any libvirt internal header files. + #include "buf.h" + + static int + myInternalFunc() The actual code. + { + ... + +Of particular note: **Do not** include libvirt/libvirt.h, +libvirt/virterror.h, libvirt/libvirt-qemu.h, or +libvirt/libvirt-lxc.h. They are included by "internal.h" already +and there are some special reasons why you cannot include these +files explicitly. One of the special cases, "libvirt/libvirt.h" is +included prior to "internal.h" in "remote_protocol.x", to avoid +exposing \*_LAST enum elements. + +Printf-style functions +---------------------- + +Whenever you add a new printf-style function, i.e., one with a +format string argument and following "..." in its prototype, be +sure to use gcc's printf attribute directive in the prototype. For +example, here's the one for virCommandAddEnvFormat in +vircommand.h: + +:: + + void virCommandAddEnvFormat(virCommandPtr cmd, const char *format, ...) + G_GNUC_PRINTF(2, 3); + +This makes it so gcc's -Wformat and -Wformat-security options can +do their jobs and cross-check format strings with the number and +types of arguments. + +When printing to a string, consider using GString or virBuffer for +incremental allocations, g_strdup_printf for a one-shot +allocation, and g_snprintf for fixed-width buffers. Only use +g_sprintf, if you can prove the buffer won't overflow. + +Error message format +-------------------- + +Error messages visible to the user should be short and +descriptive. All error messages are translated using gettext and +thus must be wrapped in ``_()`` macro. To simplify the translation +work, the error message must not be concatenated from various +parts. To simplify searching for the error message in the code the +strings should not be broken even if they result into a line +longer than 80 columns and any formatting modifier should be +enclosed by quotes or other obvious separator. If a string used +with ``%s`` can be NULL the NULLSTR macro must be used. + +:: + + GOOD: virReportError(VIR_ERR_INTERNAL_ERROR, + _("Failed to connect to remote host '%s'"), hostname) + + BAD: virReportError(VIR_ERR_INTERNAL_ERROR, + _("Failed to %s to remote host '%s'"), + "connect", hostname); + + BAD: virReportError(VIR_ERR_INTERNAL_ERROR, + _("Failed to connect " + "to remote host '%s'), + hostname); + +Use of goto +----------- + +The use of goto is not forbidden, and goto is widely used +throughout libvirt. While the uncontrolled use of goto will +quickly lead to unmaintainable code, there is a place for it in +well structured code where its use increases readability and +maintainability. In general, if goto is used for error recovery, +it's likely to be ok, otherwise, be cautious or avoid it all +together. + +The typical use of goto is to jump to cleanup code in the case of +a long list of actions, any of which may fail and cause the entire +operation to fail. In this case, a function will have a single +label at the end of the function. It's almost always ok to use +this style. In particular, if the cleanup code only involves +free'ing memory, then having multiple labels is overkill. g_free() +and most of the functions named XXXFree() in libvirt is required +to handle NULL as its arg. This does not apply to libvirt's public +APIs. Thus you can safely call free on all the variables even if +they were not yet allocated (yes they have to have been +initialized to NULL). This is much simpler and clearer than having +multiple labels. Note that most of libvirt's type declarations can +be marked with either ``g_autofree`` or ``g_autoptr`` which uses +the compiler's ``__attribute__((cleanup))`` that calls the +appropriate free function when the variable goes out of scope. + +There are a couple of signs that a particular use of goto is not +ok: + +- You're using multiple labels. If you find yourself using + multiple labels, you're strongly encouraged to rework your code + to eliminate all but one of them. +- The goto jumps back up to a point above the current line of + code being executed. Please use some combination of looping + constructs to re-execute code instead; it's almost certainly + going to be more understandable by others. One well-known + exception to this rule is restarting an i/o operation following + EINTR. +- The goto jumps down to an arbitrary place in the middle of a + function followed by further potentially failing calls. You + should almost certainly be using a conditional and a block + instead of a goto. Perhaps some of your function's logic would + be better pulled out into a helper function. + +Although libvirt does not encourage the Linux kernel wind/unwind +style of multiple labels, there's a good general discussion of the +issue archived at +`KernelTrap <http://kerneltrap.org/node/553/2131>`__ + +When using goto, please use one of these standard labels if it +makes sense: + +:: + + error: A path only taken upon return with an error code + cleanup: A path taken upon return with success code + optional error + no_memory: A path only taken upon return with an OOM error code + retry: If needing to jump upwards (e.g., retry on EINTR) + +Top-level labels should be indented by one space (putting them on +the beginning of the line confuses function context detection in +git): + +:: + + int foo() + { + /* ... do stuff ... */ + cleanup: + /* ... do other stuff ... */ + } + +Libvirt committer guidelines +============================ + +The AUTHORS files indicates the list of people with commit access +right who can actually merge the patches. + +The general rule for committing a patch is to make sure it has +been reviewed properly in the mailing-list first, usually if a +couple of people gave an ACK or +1 to a patch and nobody raised an +objection on the list it should be good to go. If the patch +touches a part of the code where you're not the main maintainer, +or where you do not have a very clear idea of how things work, +it's better to wait for a more authoritative feedback though. +Before committing, please also rebuild locally, run 'make check +syntax-check', and make sure you don't raise errors. + +An exception to 'review and approval on the list first' is fixing +failures to build: + +- if a recently committed patch breaks compilation on a platform + or for a given driver, then it's fine to commit a minimal fix + directly without getting the review feedback first +- if make check or make syntax-check breaks, if there is an + obvious fix, it's fine to commit immediately. The patch should + still be sent to the list (or tell what the fix was if + trivial), and 'make check syntax-check' should pass too, before + committing anything +- fixes for documentation and code comments can be managed in the + same way, but still make sure they get reviewed if non-trivial. +- (ir)regular pulls from other repositories or automated updates, + such as the keycodemap submodule updates, pulling in new + translations or updating the container images for the CI system -- 2.25.1
On Mon, Apr 06, 2020 at 06:20:01PM +0200, Andrea Bolognani wrote:
The conversion has been performed by using pandoc as a first pass, and then tweaking the result manually until it looked satisfactory.
Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- build-aux/syntax-check.mk | 4 +- docs/hacking.html.in | 1555 ------------------------------------- docs/hacking.rst | 1400 +++++++++++++++++++++++++++++++++ 3 files changed, 1402 insertions(+), 1557 deletions(-) delete mode 100644 docs/hacking.html.in create mode 100644 docs/hacking.rst
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
diff --git a/docs/hacking.rst b/docs/hacking.rst new file mode 100644 index 0000000000..ac02e9ab73 --- /dev/null +++ b/docs/hacking.rst @@ -0,0 +1,1400 @@ +====================== +Contributor guidelines +====================== + +.. contents:: + +General tips for contributing patches +===================================== + +#. Discuss any large changes on the mailing list first. Post + patches early and listen to feedback. + +#. Official upstream repository is kept in git + (``https://libvirt.org/git/libvirt.git``) and is browsable + along with other libvirt-related repositories (e.g. + libvirt-python) `online <https://libvirt.org/git/>`__. + +#. Patches to translations are maintained via the `zanata + project <https://fedora.zanata.org/>`__. If you want to fix a + translation in a .po file, join the appropriate language team. + The libvirt release process automatically pulls the latest + version of each translation file from zanata. + +#. The simplest way to send patches is to use the + `git-publish <https://github.com/stefanha/git-publish>`__ + tool. All libvirt-related repositories contain a config file + that tells git-publish to use the correct mailing list and + subject prefix. + + Alternatively, you may send patches using ``git send-email``. + + Also, for code motion patches, you may find that + ``git diff --patience`` provides an easier-to-read + patch. However, the usual workflow of libvirt developer is: + + :: + + git checkout master + git pull + git checkout -t origin -b workbranch + Hack, committing any changes along the way + + More hints on compiling can be found `here <compiling.html>`__. + When you want to post your patches: + + :: + + git pull --rebase + (fix any conflicts) + git send-email --cover-letter --no-chain-reply-to --annotate \ + --confirm=always --to=libvir-list@redhat.com master + + For a single patch you can omit ``--cover-letter``, but a + series of two or more patches needs a cover letter. + + Note that the ``git send-email`` subcommand may not be in the + main git package and using it may require installation of a + separate package, for example the "git-email" package in Fedora + and Debian. If this is your first time using + ``git send-email``, you might need to configure it to point it + to your SMTP server with something like: + + :: + + git config --global sendemail.smtpServer stmp.youremailprovider.net + + If you get tired of typing ``--to=libvir-list@redhat.com`` all + the time, you can configure that to be automatically handled as + well: + + :: + + git config sendemail.to libvir-list@redhat.com + + As a rule, patches should be sent to the mailing list only: all + developers are subscribed to libvir-list and read it regularly, + so **please don't CC individual developers** unless they've + explicitly asked you to. + + Avoid using mail clients for sending patches, as most of them + will mangle the messages in some way, making them unusable for + our purposes. Gmail and other Web-based mail clients are + particularly bad at this. + + If everything went well, your patch should show up on the + `libvir-list + archives <https://www.redhat.com/archives/libvir-list/>`__ in a + matter of minutes; if you still can't find it on there after an + hour or so, you should double-check your setup. **Note that, if + you are not already a subscriber, your very first post to the + mailing list will be subject to moderation**, and it's not + uncommon for that to take around a day. + + Please follow this as close as you can, especially the rebase + and ``git send-email`` part, as it makes life easier for other + developers to review your patch set. + + One should avoid sending patches as attachments, but rather + send them in email body along with commit message. If a + developer is sending another version of the patch (e.g. to + address review comments), they are advised to note differences + to previous versions after the ``---`` line in the patch so + that it helps reviewers but doesn't become part of git history. + Moreover, such patch needs to be prefixed correctly with + ``--subject-prefix=PATCHv2`` appended to + ``git send-email`` (substitute ``v2`` with the + correct version if needed though). + +#. In your commit message, make the summary line reasonably short + (60 characters is typical), followed by a blank line, followed + by any longer description of why your patch makes sense. If the + patch fixes a regression, and you know what commit introduced + the problem, mentioning that is useful. If the patch resolves a + bugzilla report, mentioning the URL of the bug number is + useful; but also summarize the issue rather than making all + readers follow the link. You can use 'git shortlog -30' to get + an idea of typical summary lines. + +#. Contributors to libvirt projects **must** assert that they are + in compliance with the `Developer Certificate of Origin + 1.1 <https://developercertificate.org/>`__. This is achieved by + adding a "Signed-off-by" line containing the contributor's name + and e-mail to every commit message. The presence of this line + attests that the contributor has read the above lined DCO and + agrees with its statements. + +#. Split large changes into a series of smaller patches, + self-contained if possible, with an explanation of each patch + and an explanation of how the sequence of patches fits + together. Moreover, please keep in mind that it's required to + be able to compile cleanly (**including** + ``make check`` and ``make syntax-check``) after each + patch. A feature does not have to work until the end of a + series, but intermediate patches must compile and not cause + test-suite failures (this is to preserve the usefulness of + ``git bisect``, among other things). + +#. Make sure your patches apply against libvirt GIT. Developers + only follow GIT and don't care much about released versions. + +#. Run the automated tests on your code before submitting any + changes. That is: + + :: + + make check + make syntax-check + make -C tests valgrind + + `Valgrind <http://valgrind.org/>`__ is a test that checks for + memory management issues, such as leaks or use of uninitialized + variables. + + Some tests are skipped by default in a development environment, + based on the time they take in comparison to the likelihood + that those tests will turn up problems during incremental + builds. These tests default to being run when building from a + tarball or with the configure option --enable-expensive-tests; + you can also force a one-time toggle of these tests by setting + VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in: + + :: + + make check VIR_TEST_EXPENSIVE=1 + + If you encounter any failing tests, the VIR_TEST_DEBUG + environment variable may provide extra information to debug the + failures. Larger values of VIR_TEST_DEBUG may provide larger + amounts of information: + + :: + + VIR_TEST_DEBUG=1 make check (or) + VIR_TEST_DEBUG=2 make check + + When debugging failures during development, it is possible to + focus in on just the failing subtests by using VIR_TEST_RANGE. + I.e. to run all tests from 3 to 20 with the exception of tests + 6 and 16, use: + + :: + + VIR_TEST_DEBUG=1 VIR_TEST_RANGE=3-5,7-20,^16 ./run tests/qemuxml2argvtest + + Also, individual tests can be run from inside the ``tests/`` + directory, like: + + :: + + ./qemuxml2xmltest + + If you are adding new test cases, or making changes that alter + existing test output, you can use the environment variable + VIR_TEST_REGENERATE_OUTPUT to quickly update the saved test + data. Of course you still need to review the changes VERY + CAREFULLY to ensure they are correct. + + :: + + VIR_TEST_REGENERATE_OUTPUT=1 ./qemuxml2argvtest + + There is also a ``./run`` script at the top level, to make it + easier to run programs that have not yet been installed, as + well as to wrap invocations of various tests under gdb or + Valgrind. + + When running our test suite it may happen that the test result + is nondeterministic because of the test suite relying on a + particular file in the system being accessible or having some + specific value. To catch this kind of errors, the test suite + has a module for that prints any path touched that fulfils + constraints described above into a file. To enable it just set + ``VIR_TEST_FILE_ACCESS`` environment variable. Then + ``VIR_TEST_FILE_ACCESS_OUTPUT`` environment variable can alter + location where the file is stored. + + :: + + VIR_TEST_FILE_ACCESS=1 VIR_TEST_FILE_ACCESS_OUTPUT="/tmp/file_access.txt" ./qemuxml2argvtest + +#. The Valgrind test should produce similar output to + ``make check``. If the output has traces within libvirt API's, + then investigation is required in order to determine the cause + of the issue. Output such as the following indicates some sort + of leak: + + :: + + ==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89 + ==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270) + ==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8) + ==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410) + ==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188) + ==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640) + ==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590) + ==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100) + ==5414== by 0x41E20F: virtTestRun (testutils.c:161) + ==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866) + ==5414== by 0x41E84A: virtTestMain (testutils.c:723) + ==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so) + + In this example, the ``virDomainDefParseXML()`` had an error + path where the ``virDomainVideoDefPtr video`` pointer was not + properly disposed. By simply adding a + ``virDomainVideoDefFree(video);`` in the error path, the issue + was resolved. + + Another common mistake is calling a printing function, such as + ``VIR_DEBUG()`` without initializing a variable to be printed. + The following example involved a call which could return an + error, but not set variables passed by reference to the call. + The solution was to initialize the variables prior to the call. + + :: + + ==4749== Use of uninitialised value of size 8 + ==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so) + ==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so) + ==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so) + ==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199) + ==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814) + ==4749== by 0x4C8AA96: virLogMessage (virlog.c:751) + ==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225) + ==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439) + ==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562) + ==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927) + ==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467) + ==4749== by 0x40AB8F: virtTestRun (testutils.c:161) + + Valgrind will also find some false positives or code paths + which cannot be resolved by making changes to the libvirt code. + For these paths, it is possible to add a filter to avoid the + errors. For example: + + :: + + ==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20 + ==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270) + ==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so) + ==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1) + ==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1) + ==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so) + ==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so) + ==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so) + + In this instance, it is acceptable to modify the + ``tests/.valgrind.supp`` file in order to add a suppression + filter. The filter should be unique enough to not suppress real + leaks, but it should be generic enough to cover multiple code + paths. The format of the entry can be found in the + documentation found at the `Valgrind home + page <http://valgrind.org/>`__. The following trace was added + to ``tests/.valgrind.supp`` in order to suppress the warning: + + :: + + { + dlInitMemoryLeak1 + Memcheck:Leak + fun:?alloc + ... + fun:call_init.part.0 + fun:_dl_init + ... + obj:*/lib*/ld-2.*so* + } + +#. Update tests and/or documentation, particularly if you are + adding a new feature or changing the output of a program. + +#. Don't forget to update the `release notes <news.html>`__ by + changing ``docs/news.xml`` if your changes are significant. All + user-visible changes, such as adding new XML elements or fixing + all but the most obscure bugs, must be (briefly) described in a + release notes entry; changes that are only relevant to other + libvirt developers, such as code refactoring, don't belong in + the release notes. Note that ``docs/news.xml`` should be + updated in its own commit not to get in the way of backports. + +There is more on this subject, including lots of links to +background reading on the subject, on `Richard Jones' guide to +working with open source +projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. + +Language Usage +============== + +The libvirt repository makes use of a large number of programming +languages. It is anticipated that in the future libvirt will adopt +use of other new languages. To reduce the overall burden on +developers, there is thus a general desire to phase out usage of +some of the existing languages. + +The preferred languages at this time are: + +- C - for the main libvirt codebase. Dialect supported by + GCC/CLang only. +- Python - for supporting build scripts / tools. Code must run + with both version 2.7 and 3.x at this time. + +Languages that should not be used for any new contributions: + +- Perl - build scripts must be written in Python instead. +- Shell - build scripts must be written in Python instead. + +Tooling +======= + +libvirt includes support for some useful development tools right +in its source repository, meaning users will be able to take +advantage of them without little or no configuration. Examples +include: + +- `color_coded <https://github.com/jeaye/color_coded>`__, a vim + plugin for libclang-powered semantic syntax highlighting; +- `YouCompleteMe <http://valloric.github.io/YouCompleteMe/>`__, a + vim plugin for libclang-powered semantic code completion. + +Naming conventions +================== + +When reading libvirt code, a number of different naming +conventions will be evident due to various changes in thinking +over the course of the project's lifetime. The conventions +documented below should be followed when creating any entirely new +files in libvirt. When working on existing files, while it is +desirable to apply these conventions, keeping a consistent style +with existing code in that particular file is generally more +important. The overall guiding principal is that every file, enum, +struct, function, macro and typedef name must have a 'vir' or +'VIR' prefix. All local scope variable names are exempt, and +global variables are exempt, unless exported in a header file. + +File names + File naming varies depending on the subdirectory. The preferred + style is to have a 'vir' prefix, followed by a name which + matches the name of the functions / objects inside the file. + For example, a file containing an object 'virHashtable' is + stored in files 'virhashtable.c' and 'virhashtable.h'. + Sometimes, methods which would otherwise be declared 'static' + need to be exported for use by a test suite. For this purpose a + second header file should be added with a suffix of 'priv', + e.g. 'virhashtablepriv.h'. Use of underscores in file names is + discouraged when using the 'vir' prefix style. The 'vir' prefix + naming applies to src/util, src/rpc and tests/ directories. + Most other directories do not follow this convention. + +Enum type & field names + All enums should have a 'vir' prefix in their typedef name, and + each following word should have its first letter in uppercase. + The enum name should match the typedef name with a leading + underscore. The enum member names should be in all uppercase, + and use an underscore to separate each word. The enum member + name prefix should match the enum typedef name. + + :: + + typedef enum _virSocketType virSocketType; + enum _virSocketType { + VIR_SOCKET_TYPE_IPV4, + VIR_SOCKET_TYPE_IPV6, + }; + +Struct type names + All structs should have a 'vir' prefix in their typedef name, + and each following word should have its first letter in + uppercase. The struct name should be the same as the typedef + name with a leading underscore. A second typedef should be + given for a pointer to the struct with a 'Ptr' suffix. + + :: + + typedef struct _virHashTable virHashTable; + typedef virHashTable *virHashTablePtr; + struct _virHashTable { + ... + }; + +Function names + All functions should have a 'vir' prefix in their name, + followed by one or more words with first letter of each word + capitalized. Underscores should not be used in function names. + If the function is operating on an object, then the function + name prefix should match the object typedef name, otherwise it + should match the filename. Following this comes the verb / + action name, and finally an optional subject name. For example, + given an object 'virHashTable', all functions should have a + name 'virHashTable$VERB' or 'virHashTable$VERB$SUBJECT", e.g. + 'virHashTableLookup' or 'virHashTableGetValue'. + +Macro names + All macros should have a "VIR" prefix in their name, followed + by one or more uppercase words separated by underscores. The + macro argument names should be in lowercase. Aside from having + a "VIR" prefix there are no common practices for the rest of + the macro name. + +Code indentation +================ + +Libvirt's C source code generally adheres to some basic +code-formatting conventions. The existing code base is not totally +consistent on this front, but we do prefer that contributed code +be formatted similarly. In short, use spaces-not-TABs for +indentation, use 4 spaces for each indentation level, and other +than that, follow the K&R style. + +If you use Emacs, the project includes a file .dir-locals.el that +sets up the preferred indentation. If you use vim, append the +following to your ~/.vimrc file: + +:: + + set nocompatible + filetype on + set autoindent + set smartindent + set cindent + set tabstop=8 + set shiftwidth=4 + set expandtab + set cinoptions=(0,:0,l1,t0,L3 + filetype plugin indent on + au FileType make setlocal noexpandtab + au BufRead,BufNewFile *.am setlocal noexpandtab + match ErrorMsg /\s\+$\| \+\ze\t/ + +Or if you don't want to mess your ~/.vimrc up, you can save the +above into a file called .lvimrc (not .vimrc) located at the root +of libvirt source, then install a vim script from +http://www.vim.org/scripts/script.php?script_id=1408, which will +load the .lvimrc only when you edit libvirt code. + +Code formatting (especially for new code) +========================================= + +With new code, we can be even more strict. Please apply the +following function (using GNU indent) to any new code. Note that +this also gives you an idea of the type of spacing we prefer +around operators and keywords: + +:: + + indent-libvirt() + { + indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \ + -sbi4 -psl -saf -sai -saw -sbi4 -ss -sc -cdw -cli4 -npcs -nbc \ + --no-tabs "$@" + } + +Note that sometimes you'll have to post-process that output +further, by piping it through ``expand -i``, since some leading +TABs can get through. Usually they're in macro definitions or +strings, and should be converted anyhow. + +Libvirt requires a C99 compiler for various reasons. However, most +of the code base prefers to stick to C89 syntax unless there is a +compelling reason otherwise. For example, it is preferable to use +``/* */`` comments rather than ``//``. Also, when declaring local +variables, the prevailing style has been to declare them at the +beginning of a scope, rather than immediately before use. + +Bracket spacing +--------------- + +The keywords ``if``, ``for``, ``while``, and ``switch`` must have +a single space following them before the opening bracket. E.g. + +:: + + if(foo) // Bad + if (foo) // Good + +Function implementations must **not** have any whitespace between +the function name and the opening bracket. E.g. + +:: + + int foo (int wizz) // Bad + int foo(int wizz) // Good + +Function calls must **not** have any whitespace between the +function name and the opening bracket. E.g. + +:: + + bar = foo (wizz); // Bad + bar = foo(wizz); // Good + +Function typedefs must **not** have any whitespace between the +closing bracket of the function name and opening bracket of the +arg list. E.g. + +:: + + typedef int (*foo) (int wizz); // Bad + typedef int (*foo)(int wizz); // Good + +There must not be any whitespace immediately following any opening +bracket, or immediately prior to any closing bracket. E.g. + +:: + + int foo( int wizz ); // Bad + int foo(int wizz); // Good + +Commas +------ + +Commas should always be followed by a space or end of line, and +never have leading space; this is enforced during 'make +syntax-check'. + +:: + + call(a,b ,c);// Bad + call(a, b, c); // Good + +When declaring an enum or using a struct initializer that occupies +more than one line, use a trailing comma. That way, future edits +to extend the list only have to add a line, rather than modify an +existing line to add the intermediate comma. Any sentinel +enumerator value with a name ending in \_LAST is exempt, since you +would extend such an enum before the \_LAST element. Another +reason to favor trailing commas is that it requires less effort to +produce via code generators. Note that the syntax checker is +unable to enforce a style of trailing commas, so there are +counterexamples in existing code which do not use it; also, while +C99 allows trailing commas, remember that JSON and XDR do not. + +:: + + enum { + VALUE_ONE, + VALUE_TWO // Bad + }; + enum { + VALUE_THREE, + VALUE_FOUR, // Good + }; + +Semicolons +---------- + +Semicolons should never have a space beforehand. Inside the +condition of a ``for`` loop, there should always be a space or +line break after each semicolon, except for the special case of an +infinite loop (although more infinite loops use ``while``). While +not enforced, loop counters generally use post-increment. + +:: + + for (i = 0 ;i < limit ; ++i) { // Bad + for (i = 0; i < limit; i++) { // Good + for (;;) { // ok + while (1) { // Better + +Empty loop bodies are better represented with curly braces and a +comment, although use of a semicolon is not currently rejected. + +:: + + while ((rc = waitpid(pid, &st, 0) == -1) && + errno == EINTR); // ok + while ((rc = waitpid(pid, &st, 0) == -1) && + errno == EINTR) { // Better + /* nothing */ + } + +Curly braces +------------ + +Omit the curly braces around an ``if``, ``while``, ``for`` etc. +body only when both that body and the condition itself occupy a +single line. In every other case we require the braces. This +ensures that it is trivially easy to identify a +single-\ *statement* loop: each has only one *line* in its body. + +:: + + while (expr) // single line body; {} is forbidden + single_line_stmt(); + +:: + + while (expr(arg1, + arg2)) // indentation makes it obvious it is single line, + single_line_stmt(); // {} is optional (not enforced either way) + +:: + + while (expr1 && + expr2) { // multi-line, at same indentation, {} required + single_line_stmt(); + } + +However, the moment your loop/if/else body extends on to a second +line, for whatever reason (even if it's just an added comment), +then you should add braces. Otherwise, it would be too easy to +insert a statement just before that comment (without adding +braces), thinking it is already a multi-statement loop: + +:: + + while (true) // BAD! multi-line body with no braces + /* comment... */ + single_line_stmt(); + +Do this instead: + +:: + + while (true) { // Always put braces around a multi-line body. + /* comment... */ + single_line_stmt(); + } + +There is one exception: when the second body line is not at the +same indentation level as the first body line: + +:: + + if (expr) + die("a diagnostic that would make this line" + " extend past the 80-column limit")); + +It is safe to omit the braces in the code above, since the +further-indented second body line makes it obvious that this is +still a single-statement body. + +To reiterate, don't do this: + +:: + + if (expr) // BAD: no braces around... + while (expr_2) { // ... a multi-line body + ... + } + +Do this, instead: + +:: + + if (expr) { + while (expr_2) { + ... + } + } + +However, there is one exception in the other direction, when even +a one-line block should have braces. That occurs when that +one-line, brace-less block is an ``if`` or ``else`` block, and the +counterpart block **does** use braces. In that case, put braces +around both blocks. Also, if the ``else`` block is much shorter +than the ``if`` block, consider negating the ``if``-condition and +swapping the bodies, putting the short block first and making the +longer, multi-line block be the ``else`` block. + +:: + + if (expr) { + ... + ... + } + else + x = y; // BAD: braceless "else" with braced "then", + // and short block last + + if (expr) + x = y; // BAD: braceless "if" with braced "else" + else { + ... + ... + } + +Keeping braces consistent and putting the short block first is +preferred, especially when the multi-line body is more than a few +lines long, because it is easier to read and grasp the semantics +of an if-then-else block when the simpler block occurs first, +rather than after the more involved block: + +:: + + if (!expr) { + x = y; // putting the smaller block first is more readable + } else { + ... + ... + } + +But if negating a complex condition is too ugly, then at least add +braces: + +:: + + if (complex expr not worth negating) { + ... + ... + } else { + x = y; + } + +Use hanging braces for compound statements: the opening brace of a +compound statement should be on the same line as the condition +being tested. Only top-level function bodies, nested scopes, and +compound structure declarations should ever have { on a line by +itself. + +:: + + void + foo(int a, int b) + { // correct - function body + int 2d[][] = { + { // correct - complex initialization + 1, 2, + }, + }; + if (a) + { // BAD: compound brace on its own line + do_stuff(); + } + { // correct - nested scope + int tmp; + if (a < b) { // correct - hanging brace + tmp = b; + b = a; + a = tmp; + } + } + } + +Conditional expressions +----------------------- + +For readability reasons new code should avoid shortening +comparisons to 0 for numeric types. Boolean and pointer +comparisions may be shortened. All long forms are okay: + +:: + + virFooPtr foos = NULL; + size nfoos = 0; + bool hasFoos = false; + + GOOD: + if (!foos) + if (!hasFoos) + if (nfoos == 0) + if (foos == NULL) + if (hasFoos == true) + + BAD: + if (!nfoos) + if (nfoos) + +New code should avoid the ternary operator as much as possible. +Specifically it must never span more than one line or nest: + +:: + + BAD: + char *foo = baz ? + virDoSomethingReallyComplex(driver, vm, something, baz->foo) : + NULL; + + char *foo = bar ? bar->baz ? bar->baz->foo : "nobaz" : "nobar"; + +Preprocessor +------------ + +Macros defined with an ALL_CAPS name should generally be assumed +to be unsafe with regards to arguments with side-effects (that is, +MAX(a++, b--) might increment a or decrement b too many or too few +times). Exceptions to this rule are explicitly documented for +macros in viralloc.h and virstring.h. + +For variadic macros, stick with C99 syntax: + +:: + + #define vshPrint(_ctl, ...) fprintf(stdout, __VA_ARGS__) + +Use parenthesis when checking if a macro is defined, and use +indentation to track nesting: + +:: + + #if defined(HAVE_POSIX_FALLOCATE) && !defined(HAVE_FALLOCATE) + # define fallocate(a, ignored, b, c) posix_fallocate(a, b, c) + #endif + +C types +------- + +Use the right type. + +Scalars +^^^^^^^
Our style guide (docs/styleguide.rst) calls for "~~~~~~~" for level 4
+Pointers +^^^^^^^^
With the two headings changed Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
This part is very specific and doesn't quite fit into the "coding style" section, so let's move it to its own page. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/glib-adoption.rst | 96 ++++++++++++++++++++++++++++++++++++++++++ docs/hacking.rst | 96 ------------------------------------------ 2 files changed, 96 insertions(+), 96 deletions(-) create mode 100644 docs/glib-adoption.rst diff --git a/docs/glib-adoption.rst b/docs/glib-adoption.rst new file mode 100644 index 0000000000..62ddd7c61d --- /dev/null +++ b/docs/glib-adoption.rst @@ -0,0 +1,96 @@ +===================== +Adoption of GLib APIs +===================== + +Libvirt has adopted use of the `GLib +library <https://developer.gnome.org/glib/stable/>`__. Due to +libvirt's long history of development, there are many APIs in +libvirt, for which GLib provides an alternative solution. The +general rule to follow is that the standard GLib solution will be +preferred over historical libvirt APIs. Existing code will be +ported over to use GLib APIs over time, but new code should use +the GLib APIs straight away where possible. + +The following is a list of libvirt APIs that should no longer be +used in new code, and their suggested GLib replacements: + +``VIR_ALLOC``, ``VIR_REALLOC``, ``VIR_RESIZE_N``, ``VIR_EXPAND_N``, ``VIR_SHRINK_N``, ``VIR_FREE``, ``VIR_APPEND_ELEMENT``, ``VIR_INSERT_ELEMENT``, ``VIR_DELETE_ELEMENT`` + Prefer the GLib APIs ``g_new0``/``g_renew``/ ``g_free`` in most + cases. There should rarely be a need to use + ``g_malloc``/``g_realloc``. Instead of using plain C arrays, it + is preferrable to use one of the GLib types, ``GArray``, + ``GPtrArray`` or ``GByteArray``. These all use a struct to + track the array memory and size together and efficiently + resize. **NEVER MIX** use of the classic libvirt memory + allocation APIs and GLib APIs within a single method. Keep the + style consistent, converting existing code to GLib style in a + separate, prior commit. +``virStrerror`` + The GLib ``g_strerror()`` function should be used instead, + which has a simpler calling convention as an added benefit. + +The following libvirt APIs have been deleted already: + +``VIR_AUTOPTR``, ``VIR_AUTOCLEAN``, ``VIR_AUTOFREE`` + The GLib macros ``g_autoptr``, ``g_auto`` and ``g_autofree`` + must be used instead in all new code. In existing code, the + GLib macros must never be mixed with libvirt macros within a + method, nor should they be mixed with ``VIR_FREE``. If + introducing GLib macros to an existing method, any use of + libvirt macros must be converted in an independent commit. +``VIR_DEFINE_AUTOPTR_FUNC``, ``VIR_DEFINE_AUTOCLEAN_FUNC`` + The GLib macros ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` and + ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` must be used in all new + code. Existing code should be converted to the new macros where + relevant. It is permissible to use ``g_autoptr``, ``g_auto`` on + an object whose cleanup function is declared with the libvirt + macros and vice-versa. +``VIR_AUTOUNREF`` + The GLib macros ``g_autoptr`` and + ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` should be used to manage + autoclean of virObject classes. This matches usage with GObject + classes. +``VIR_STRDUP``, ``VIR_STRNDUP`` + Prefer the GLib APIs ``g_strdup`` and ``g_strndup``. + ++-------------------------------+--------------------------------------+-------------------------------------------+ +| deleted version | GLib version | Notes | ++===============================+======================================+===========================================+ +| ``VIR_AUTOPTR`` | ``g_autoptr`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOCLEAN`` | ``g_auto`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOFREE`` | ``g_autofree`` | The GLib version does not use parentheses | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_AUTOUNREF`` | ``g_autoptr`` | The cleanup function needs to be defined | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_DEFINE_AUTOPTR_FUNC`` | ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_DEFINE_AUTOCLEAN_FUNC`` | ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STEAL_PTR`` | ``g_steal_pointer`` | ``a = f(&b)`` instead of ``f(a, b)`` | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_RETURN_PTR`` | ``return g_steal_pointer`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ARRAY_CARDINALITY`` | ``G_N_ELEMENTS`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_FALLTHROUGH`` | ``G_GNUC_FALLTHROUGH`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_FMT_PRINTF`` | ``G_GNUC_PRINTF`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_NOINLINE`` | ``G_GNUC_NO_INLINE`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_NORETURN`` | ``G_GNUC_NORETURN`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_RETURN_CHECK`` | ``G_GNUC_WARN_UNUSED_RESULT`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_SENTINEL`` | ``G_GNUC_NULL_TERMINATED`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``ATTRIBUTE_UNUSED`` | ``G_GNUC_UNUSED`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STRDUP`` | ``g_strdup`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``VIR_STRNDUP`` | ``g_strndup`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ +| ``virStrerror`` | ``g_strerror`` | | ++-------------------------------+--------------------------------------+-------------------------------------------+ diff --git a/docs/hacking.rst b/docs/hacking.rst index ac02e9ab73..4067b282a3 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -921,102 +921,6 @@ analysis tools understand the code better: | ``G_GNUC_WARN_UNUSED_RESULT`` | the return value must be checked | +-------------------------------+------------------------------------------------------------+ -Adoption of GLib APIs ---------------------- - -Libvirt has adopted use of the `GLib -library <https://developer.gnome.org/glib/stable/>`__. Due to -libvirt's long history of development, there are many APIs in -libvirt, for which GLib provides an alternative solution. The -general rule to follow is that the standard GLib solution will be -preferred over historical libvirt APIs. Existing code will be -ported over to use GLib APIs over time, but new code should use -the GLib APIs straight away where possible. - -The following is a list of libvirt APIs that should no longer be -used in new code, and their suggested GLib replacements: - -``VIR_ALLOC``, ``VIR_REALLOC``, ``VIR_RESIZE_N``, ``VIR_EXPAND_N``, ``VIR_SHRINK_N``, ``VIR_FREE``, ``VIR_APPEND_ELEMENT``, ``VIR_INSERT_ELEMENT``, ``VIR_DELETE_ELEMENT`` - Prefer the GLib APIs ``g_new0``/``g_renew``/ ``g_free`` in most - cases. There should rarely be a need to use - ``g_malloc``/``g_realloc``. Instead of using plain C arrays, it - is preferrable to use one of the GLib types, ``GArray``, - ``GPtrArray`` or ``GByteArray``. These all use a struct to - track the array memory and size together and efficiently - resize. **NEVER MIX** use of the classic libvirt memory - allocation APIs and GLib APIs within a single method. Keep the - style consistent, converting existing code to GLib style in a - separate, prior commit. -``virStrerror`` - The GLib ``g_strerror()`` function should be used instead, - which has a simpler calling convention as an added benefit. - -The following libvirt APIs have been deleted already: - -``VIR_AUTOPTR``, ``VIR_AUTOCLEAN``, ``VIR_AUTOFREE`` - The GLib macros ``g_autoptr``, ``g_auto`` and ``g_autofree`` - must be used instead in all new code. In existing code, the - GLib macros must never be mixed with libvirt macros within a - method, nor should they be mixed with ``VIR_FREE``. If - introducing GLib macros to an existing method, any use of - libvirt macros must be converted in an independent commit. -``VIR_DEFINE_AUTOPTR_FUNC``, ``VIR_DEFINE_AUTOCLEAN_FUNC`` - The GLib macros ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` and - ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` must be used in all new - code. Existing code should be converted to the new macros where - relevant. It is permissible to use ``g_autoptr``, ``g_auto`` on - an object whose cleanup function is declared with the libvirt - macros and vice-versa. -``VIR_AUTOUNREF`` - The GLib macros ``g_autoptr`` and - ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` should be used to manage - autoclean of virObject classes. This matches usage with GObject - classes. -``VIR_STRDUP``, ``VIR_STRNDUP`` - Prefer the GLib APIs ``g_strdup`` and ``g_strndup``. - -+-------------------------------+--------------------------------------+-------------------------------------------+ -| deleted version | GLib version | Notes | -+===============================+======================================+===========================================+ -| ``VIR_AUTOPTR`` | ``g_autoptr`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_AUTOCLEAN`` | ``g_auto`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_AUTOFREE`` | ``g_autofree`` | The GLib version does not use parentheses | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_AUTOUNREF`` | ``g_autoptr`` | The cleanup function needs to be defined | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_DEFINE_AUTOPTR_FUNC`` | ``G_DEFINE_AUTOPTR_CLEANUP_FUNC`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_DEFINE_AUTOCLEAN_FUNC`` | ``G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_STEAL_PTR`` | ``g_steal_pointer`` | ``a = f(&b)`` instead of ``f(a, b)`` | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_RETURN_PTR`` | ``return g_steal_pointer`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ARRAY_CARDINALITY`` | ``G_N_ELEMENTS`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ATTRIBUTE_FALLTHROUGH`` | ``G_GNUC_FALLTHROUGH`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ATTRIBUTE_FMT_PRINTF`` | ``G_GNUC_PRINTF`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ATTRIBUTE_NOINLINE`` | ``G_GNUC_NO_INLINE`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ATTRIBUTE_NORETURN`` | ``G_GNUC_NORETURN`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ATTRIBUTE_RETURN_CHECK`` | ``G_GNUC_WARN_UNUSED_RESULT`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ATTRIBUTE_SENTINEL`` | ``G_GNUC_NULL_TERMINATED`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``ATTRIBUTE_UNUSED`` | ``G_GNUC_UNUSED`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_STRDUP`` | ``g_strdup`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``VIR_STRNDUP`` | ``g_strndup`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ -| ``virStrerror`` | ``g_strerror`` | | -+-------------------------------+--------------------------------------+-------------------------------------------+ - File handling ------------- -- 2.25.1
On Mon, Apr 06, 2020 at 06:20:02PM +0200, Andrea Bolognani wrote:
This part is very specific and doesn't quite fit into the "coding style" section, so let's move it to its own page.
Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/glib-adoption.rst | 96 ++++++++++++++++++++++++++++++++++++++++++ docs/hacking.rst | 96 ------------------------------------------ 2 files changed, 96 insertions(+), 96 deletions(-) create mode 100644 docs/glib-adoption.rst
Nitpick that this new page is an orphan until the last patch, but I can understand why you did that and I think it is ok. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
This part represents the biggest chunk of the existing hacking.rst, and despite that its utility is very limited because 'make syntax-check' already guarantees most of the rules are followed over time. Until the glorious day we finally codify our coding style completely into a configuration for a tool such as clang-format and thus no longer need a plain English description of it, move this part to a separate page. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- build-aux/syntax-check.mk | 2 +- docs/{hacking.rst => coding-style.rst} | 391 +---------- docs/hacking.rst | 914 ------------------------- 3 files changed, 4 insertions(+), 1303 deletions(-) copy docs/{hacking.rst => coding-style.rst} (64%) diff --git a/build-aux/syntax-check.mk b/build-aux/syntax-check.mk index 6ffea7afb9..8bee1bbbf1 100644 --- a/build-aux/syntax-check.mk +++ b/build-aux/syntax-check.mk @@ -2048,7 +2048,7 @@ exclude_file_name_regexp--sc_prohibit_readlink = \ exclude_file_name_regexp--sc_prohibit_setuid = ^src/util/virutil\.c|tools/virt-login-shell\.c$$ exclude_file_name_regexp--sc_prohibit_snprintf = \ - ^(build-aux/syntax-check\.mk|docs/hacking\.rst|tools/virt-login-shell\.c)$$ + ^(build-aux/syntax-check\.mk|docs/coding-style\.rst|tools/virt-login-shell\.c)$$ exclude_file_name_regexp--sc_prohibit_strtol = ^examples/.*$$ diff --git a/docs/hacking.rst b/docs/coding-style.rst similarity index 64% copy from docs/hacking.rst copy to docs/coding-style.rst index 4067b282a3..04baf9473c 100644 --- a/docs/hacking.rst +++ b/docs/coding-style.rst @@ -1,361 +1,9 @@ -====================== -Contributor guidelines -====================== +============ +Coding style +============ .. contents:: -General tips for contributing patches -===================================== - -#. Discuss any large changes on the mailing list first. Post - patches early and listen to feedback. - -#. Official upstream repository is kept in git - (``https://libvirt.org/git/libvirt.git``) and is browsable - along with other libvirt-related repositories (e.g. - libvirt-python) `online <https://libvirt.org/git/>`__. - -#. Patches to translations are maintained via the `zanata - project <https://fedora.zanata.org/>`__. If you want to fix a - translation in a .po file, join the appropriate language team. - The libvirt release process automatically pulls the latest - version of each translation file from zanata. - -#. The simplest way to send patches is to use the - `git-publish <https://github.com/stefanha/git-publish>`__ - tool. All libvirt-related repositories contain a config file - that tells git-publish to use the correct mailing list and - subject prefix. - - Alternatively, you may send patches using ``git send-email``. - - Also, for code motion patches, you may find that - ``git diff --patience`` provides an easier-to-read - patch. However, the usual workflow of libvirt developer is: - - :: - - git checkout master - git pull - git checkout -t origin -b workbranch - Hack, committing any changes along the way - - More hints on compiling can be found `here <compiling.html>`__. - When you want to post your patches: - - :: - - git pull --rebase - (fix any conflicts) - git send-email --cover-letter --no-chain-reply-to --annotate \ - --confirm=always --to=libvir-list@redhat.com master - - For a single patch you can omit ``--cover-letter``, but a - series of two or more patches needs a cover letter. - - Note that the ``git send-email`` subcommand may not be in the - main git package and using it may require installation of a - separate package, for example the "git-email" package in Fedora - and Debian. If this is your first time using - ``git send-email``, you might need to configure it to point it - to your SMTP server with something like: - - :: - - git config --global sendemail.smtpServer stmp.youremailprovider.net - - If you get tired of typing ``--to=libvir-list@redhat.com`` all - the time, you can configure that to be automatically handled as - well: - - :: - - git config sendemail.to libvir-list@redhat.com - - As a rule, patches should be sent to the mailing list only: all - developers are subscribed to libvir-list and read it regularly, - so **please don't CC individual developers** unless they've - explicitly asked you to. - - Avoid using mail clients for sending patches, as most of them - will mangle the messages in some way, making them unusable for - our purposes. Gmail and other Web-based mail clients are - particularly bad at this. - - If everything went well, your patch should show up on the - `libvir-list - archives <https://www.redhat.com/archives/libvir-list/>`__ in a - matter of minutes; if you still can't find it on there after an - hour or so, you should double-check your setup. **Note that, if - you are not already a subscriber, your very first post to the - mailing list will be subject to moderation**, and it's not - uncommon for that to take around a day. - - Please follow this as close as you can, especially the rebase - and ``git send-email`` part, as it makes life easier for other - developers to review your patch set. - - One should avoid sending patches as attachments, but rather - send them in email body along with commit message. If a - developer is sending another version of the patch (e.g. to - address review comments), they are advised to note differences - to previous versions after the ``---`` line in the patch so - that it helps reviewers but doesn't become part of git history. - Moreover, such patch needs to be prefixed correctly with - ``--subject-prefix=PATCHv2`` appended to - ``git send-email`` (substitute ``v2`` with the - correct version if needed though). - -#. In your commit message, make the summary line reasonably short - (60 characters is typical), followed by a blank line, followed - by any longer description of why your patch makes sense. If the - patch fixes a regression, and you know what commit introduced - the problem, mentioning that is useful. If the patch resolves a - bugzilla report, mentioning the URL of the bug number is - useful; but also summarize the issue rather than making all - readers follow the link. You can use 'git shortlog -30' to get - an idea of typical summary lines. - -#. Contributors to libvirt projects **must** assert that they are - in compliance with the `Developer Certificate of Origin - 1.1 <https://developercertificate.org/>`__. This is achieved by - adding a "Signed-off-by" line containing the contributor's name - and e-mail to every commit message. The presence of this line - attests that the contributor has read the above lined DCO and - agrees with its statements. - -#. Split large changes into a series of smaller patches, - self-contained if possible, with an explanation of each patch - and an explanation of how the sequence of patches fits - together. Moreover, please keep in mind that it's required to - be able to compile cleanly (**including** - ``make check`` and ``make syntax-check``) after each - patch. A feature does not have to work until the end of a - series, but intermediate patches must compile and not cause - test-suite failures (this is to preserve the usefulness of - ``git bisect``, among other things). - -#. Make sure your patches apply against libvirt GIT. Developers - only follow GIT and don't care much about released versions. - -#. Run the automated tests on your code before submitting any - changes. That is: - - :: - - make check - make syntax-check - make -C tests valgrind - - `Valgrind <http://valgrind.org/>`__ is a test that checks for - memory management issues, such as leaks or use of uninitialized - variables. - - Some tests are skipped by default in a development environment, - based on the time they take in comparison to the likelihood - that those tests will turn up problems during incremental - builds. These tests default to being run when building from a - tarball or with the configure option --enable-expensive-tests; - you can also force a one-time toggle of these tests by setting - VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in: - - :: - - make check VIR_TEST_EXPENSIVE=1 - - If you encounter any failing tests, the VIR_TEST_DEBUG - environment variable may provide extra information to debug the - failures. Larger values of VIR_TEST_DEBUG may provide larger - amounts of information: - - :: - - VIR_TEST_DEBUG=1 make check (or) - VIR_TEST_DEBUG=2 make check - - When debugging failures during development, it is possible to - focus in on just the failing subtests by using VIR_TEST_RANGE. - I.e. to run all tests from 3 to 20 with the exception of tests - 6 and 16, use: - - :: - - VIR_TEST_DEBUG=1 VIR_TEST_RANGE=3-5,7-20,^16 ./run tests/qemuxml2argvtest - - Also, individual tests can be run from inside the ``tests/`` - directory, like: - - :: - - ./qemuxml2xmltest - - If you are adding new test cases, or making changes that alter - existing test output, you can use the environment variable - VIR_TEST_REGENERATE_OUTPUT to quickly update the saved test - data. Of course you still need to review the changes VERY - CAREFULLY to ensure they are correct. - - :: - - VIR_TEST_REGENERATE_OUTPUT=1 ./qemuxml2argvtest - - There is also a ``./run`` script at the top level, to make it - easier to run programs that have not yet been installed, as - well as to wrap invocations of various tests under gdb or - Valgrind. - - When running our test suite it may happen that the test result - is nondeterministic because of the test suite relying on a - particular file in the system being accessible or having some - specific value. To catch this kind of errors, the test suite - has a module for that prints any path touched that fulfils - constraints described above into a file. To enable it just set - ``VIR_TEST_FILE_ACCESS`` environment variable. Then - ``VIR_TEST_FILE_ACCESS_OUTPUT`` environment variable can alter - location where the file is stored. - - :: - - VIR_TEST_FILE_ACCESS=1 VIR_TEST_FILE_ACCESS_OUTPUT="/tmp/file_access.txt" ./qemuxml2argvtest - -#. The Valgrind test should produce similar output to - ``make check``. If the output has traces within libvirt API's, - then investigation is required in order to determine the cause - of the issue. Output such as the following indicates some sort - of leak: - - :: - - ==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89 - ==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270) - ==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8) - ==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410) - ==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188) - ==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640) - ==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590) - ==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100) - ==5414== by 0x41E20F: virtTestRun (testutils.c:161) - ==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866) - ==5414== by 0x41E84A: virtTestMain (testutils.c:723) - ==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so) - - In this example, the ``virDomainDefParseXML()`` had an error - path where the ``virDomainVideoDefPtr video`` pointer was not - properly disposed. By simply adding a - ``virDomainVideoDefFree(video);`` in the error path, the issue - was resolved. - - Another common mistake is calling a printing function, such as - ``VIR_DEBUG()`` without initializing a variable to be printed. - The following example involved a call which could return an - error, but not set variables passed by reference to the call. - The solution was to initialize the variables prior to the call. - - :: - - ==4749== Use of uninitialised value of size 8 - ==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so) - ==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so) - ==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so) - ==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199) - ==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814) - ==4749== by 0x4C8AA96: virLogMessage (virlog.c:751) - ==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225) - ==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439) - ==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562) - ==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927) - ==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467) - ==4749== by 0x40AB8F: virtTestRun (testutils.c:161) - - Valgrind will also find some false positives or code paths - which cannot be resolved by making changes to the libvirt code. - For these paths, it is possible to add a filter to avoid the - errors. For example: - - :: - - ==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20 - ==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270) - ==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so) - ==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1) - ==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1) - ==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so) - ==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so) - ==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so) - - In this instance, it is acceptable to modify the - ``tests/.valgrind.supp`` file in order to add a suppression - filter. The filter should be unique enough to not suppress real - leaks, but it should be generic enough to cover multiple code - paths. The format of the entry can be found in the - documentation found at the `Valgrind home - page <http://valgrind.org/>`__. The following trace was added - to ``tests/.valgrind.supp`` in order to suppress the warning: - - :: - - { - dlInitMemoryLeak1 - Memcheck:Leak - fun:?alloc - ... - fun:call_init.part.0 - fun:_dl_init - ... - obj:*/lib*/ld-2.*so* - } - -#. Update tests and/or documentation, particularly if you are - adding a new feature or changing the output of a program. - -#. Don't forget to update the `release notes <news.html>`__ by - changing ``docs/news.xml`` if your changes are significant. All - user-visible changes, such as adding new XML elements or fixing - all but the most obscure bugs, must be (briefly) described in a - release notes entry; changes that are only relevant to other - libvirt developers, such as code refactoring, don't belong in - the release notes. Note that ``docs/news.xml`` should be - updated in its own commit not to get in the way of backports. - -There is more on this subject, including lots of links to -background reading on the subject, on `Richard Jones' guide to -working with open source -projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. - -Language Usage -============== - -The libvirt repository makes use of a large number of programming -languages. It is anticipated that in the future libvirt will adopt -use of other new languages. To reduce the overall burden on -developers, there is thus a general desire to phase out usage of -some of the existing languages. - -The preferred languages at this time are: - -- C - for the main libvirt codebase. Dialect supported by - GCC/CLang only. -- Python - for supporting build scripts / tools. Code must run - with both version 2.7 and 3.x at this time. - -Languages that should not be used for any new contributions: - -- Perl - build scripts must be written in Python instead. -- Shell - build scripts must be written in Python instead. - -Tooling -======= - -libvirt includes support for some useful development tools right -in its source repository, meaning users will be able to take -advantage of them without little or no configuration. Examples -include: - -- `color_coded <https://github.com/jeaye/color_coded>`__, a vim - plugin for libclang-powered semantic syntax highlighting; -- `YouCompleteMe <http://valloric.github.io/YouCompleteMe/>`__, a - vim plugin for libclang-powered semantic code completion. - Naming conventions ================== @@ -1269,36 +917,3 @@ git): cleanup: /* ... do other stuff ... */ } - -Libvirt committer guidelines -============================ - -The AUTHORS files indicates the list of people with commit access -right who can actually merge the patches. - -The general rule for committing a patch is to make sure it has -been reviewed properly in the mailing-list first, usually if a -couple of people gave an ACK or +1 to a patch and nobody raised an -objection on the list it should be good to go. If the patch -touches a part of the code where you're not the main maintainer, -or where you do not have a very clear idea of how things work, -it's better to wait for a more authoritative feedback though. -Before committing, please also rebuild locally, run 'make check -syntax-check', and make sure you don't raise errors. - -An exception to 'review and approval on the list first' is fixing -failures to build: - -- if a recently committed patch breaks compilation on a platform - or for a given driver, then it's fine to commit a minimal fix - directly without getting the review feedback first -- if make check or make syntax-check breaks, if there is an - obvious fix, it's fine to commit immediately. The patch should - still be sent to the list (or tell what the fix was if - trivial), and 'make check syntax-check' should pass too, before - committing anything -- fixes for documentation and code comments can be managed in the - same way, but still make sure they get reviewed if non-trivial. -- (ir)regular pulls from other repositories or automated updates, - such as the keycodemap submodule updates, pulling in new - translations or updating the container images for the CI system diff --git a/docs/hacking.rst b/docs/hacking.rst index 4067b282a3..356dbc506b 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -356,920 +356,6 @@ include: - `YouCompleteMe <http://valloric.github.io/YouCompleteMe/>`__, a vim plugin for libclang-powered semantic code completion. -Naming conventions -================== - -When reading libvirt code, a number of different naming -conventions will be evident due to various changes in thinking -over the course of the project's lifetime. The conventions -documented below should be followed when creating any entirely new -files in libvirt. When working on existing files, while it is -desirable to apply these conventions, keeping a consistent style -with existing code in that particular file is generally more -important. The overall guiding principal is that every file, enum, -struct, function, macro and typedef name must have a 'vir' or -'VIR' prefix. All local scope variable names are exempt, and -global variables are exempt, unless exported in a header file. - -File names - File naming varies depending on the subdirectory. The preferred - style is to have a 'vir' prefix, followed by a name which - matches the name of the functions / objects inside the file. - For example, a file containing an object 'virHashtable' is - stored in files 'virhashtable.c' and 'virhashtable.h'. - Sometimes, methods which would otherwise be declared 'static' - need to be exported for use by a test suite. For this purpose a - second header file should be added with a suffix of 'priv', - e.g. 'virhashtablepriv.h'. Use of underscores in file names is - discouraged when using the 'vir' prefix style. The 'vir' prefix - naming applies to src/util, src/rpc and tests/ directories. - Most other directories do not follow this convention. - -Enum type & field names - All enums should have a 'vir' prefix in their typedef name, and - each following word should have its first letter in uppercase. - The enum name should match the typedef name with a leading - underscore. The enum member names should be in all uppercase, - and use an underscore to separate each word. The enum member - name prefix should match the enum typedef name. - - :: - - typedef enum _virSocketType virSocketType; - enum _virSocketType { - VIR_SOCKET_TYPE_IPV4, - VIR_SOCKET_TYPE_IPV6, - }; - -Struct type names - All structs should have a 'vir' prefix in their typedef name, - and each following word should have its first letter in - uppercase. The struct name should be the same as the typedef - name with a leading underscore. A second typedef should be - given for a pointer to the struct with a 'Ptr' suffix. - - :: - - typedef struct _virHashTable virHashTable; - typedef virHashTable *virHashTablePtr; - struct _virHashTable { - ... - }; - -Function names - All functions should have a 'vir' prefix in their name, - followed by one or more words with first letter of each word - capitalized. Underscores should not be used in function names. - If the function is operating on an object, then the function - name prefix should match the object typedef name, otherwise it - should match the filename. Following this comes the verb / - action name, and finally an optional subject name. For example, - given an object 'virHashTable', all functions should have a - name 'virHashTable$VERB' or 'virHashTable$VERB$SUBJECT", e.g. - 'virHashTableLookup' or 'virHashTableGetValue'. - -Macro names - All macros should have a "VIR" prefix in their name, followed - by one or more uppercase words separated by underscores. The - macro argument names should be in lowercase. Aside from having - a "VIR" prefix there are no common practices for the rest of - the macro name. - -Code indentation -================ - -Libvirt's C source code generally adheres to some basic -code-formatting conventions. The existing code base is not totally -consistent on this front, but we do prefer that contributed code -be formatted similarly. In short, use spaces-not-TABs for -indentation, use 4 spaces for each indentation level, and other -than that, follow the K&R style. - -If you use Emacs, the project includes a file .dir-locals.el that -sets up the preferred indentation. If you use vim, append the -following to your ~/.vimrc file: - -:: - - set nocompatible - filetype on - set autoindent - set smartindent - set cindent - set tabstop=8 - set shiftwidth=4 - set expandtab - set cinoptions=(0,:0,l1,t0,L3 - filetype plugin indent on - au FileType make setlocal noexpandtab - au BufRead,BufNewFile *.am setlocal noexpandtab - match ErrorMsg /\s\+$\| \+\ze\t/ - -Or if you don't want to mess your ~/.vimrc up, you can save the -above into a file called .lvimrc (not .vimrc) located at the root -of libvirt source, then install a vim script from -http://www.vim.org/scripts/script.php?script_id=1408, which will -load the .lvimrc only when you edit libvirt code. - -Code formatting (especially for new code) -========================================= - -With new code, we can be even more strict. Please apply the -following function (using GNU indent) to any new code. Note that -this also gives you an idea of the type of spacing we prefer -around operators and keywords: - -:: - - indent-libvirt() - { - indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \ - -sbi4 -psl -saf -sai -saw -sbi4 -ss -sc -cdw -cli4 -npcs -nbc \ - --no-tabs "$@" - } - -Note that sometimes you'll have to post-process that output -further, by piping it through ``expand -i``, since some leading -TABs can get through. Usually they're in macro definitions or -strings, and should be converted anyhow. - -Libvirt requires a C99 compiler for various reasons. However, most -of the code base prefers to stick to C89 syntax unless there is a -compelling reason otherwise. For example, it is preferable to use -``/* */`` comments rather than ``//``. Also, when declaring local -variables, the prevailing style has been to declare them at the -beginning of a scope, rather than immediately before use. - -Bracket spacing ---------------- - -The keywords ``if``, ``for``, ``while``, and ``switch`` must have -a single space following them before the opening bracket. E.g. - -:: - - if(foo) // Bad - if (foo) // Good - -Function implementations must **not** have any whitespace between -the function name and the opening bracket. E.g. - -:: - - int foo (int wizz) // Bad - int foo(int wizz) // Good - -Function calls must **not** have any whitespace between the -function name and the opening bracket. E.g. - -:: - - bar = foo (wizz); // Bad - bar = foo(wizz); // Good - -Function typedefs must **not** have any whitespace between the -closing bracket of the function name and opening bracket of the -arg list. E.g. - -:: - - typedef int (*foo) (int wizz); // Bad - typedef int (*foo)(int wizz); // Good - -There must not be any whitespace immediately following any opening -bracket, or immediately prior to any closing bracket. E.g. - -:: - - int foo( int wizz ); // Bad - int foo(int wizz); // Good - -Commas ------- - -Commas should always be followed by a space or end of line, and -never have leading space; this is enforced during 'make -syntax-check'. - -:: - - call(a,b ,c);// Bad - call(a, b, c); // Good - -When declaring an enum or using a struct initializer that occupies -more than one line, use a trailing comma. That way, future edits -to extend the list only have to add a line, rather than modify an -existing line to add the intermediate comma. Any sentinel -enumerator value with a name ending in \_LAST is exempt, since you -would extend such an enum before the \_LAST element. Another -reason to favor trailing commas is that it requires less effort to -produce via code generators. Note that the syntax checker is -unable to enforce a style of trailing commas, so there are -counterexamples in existing code which do not use it; also, while -C99 allows trailing commas, remember that JSON and XDR do not. - -:: - - enum { - VALUE_ONE, - VALUE_TWO // Bad - }; - enum { - VALUE_THREE, - VALUE_FOUR, // Good - }; - -Semicolons ----------- - -Semicolons should never have a space beforehand. Inside the -condition of a ``for`` loop, there should always be a space or -line break after each semicolon, except for the special case of an -infinite loop (although more infinite loops use ``while``). While -not enforced, loop counters generally use post-increment. - -:: - - for (i = 0 ;i < limit ; ++i) { // Bad - for (i = 0; i < limit; i++) { // Good - for (;;) { // ok - while (1) { // Better - -Empty loop bodies are better represented with curly braces and a -comment, although use of a semicolon is not currently rejected. - -:: - - while ((rc = waitpid(pid, &st, 0) == -1) && - errno == EINTR); // ok - while ((rc = waitpid(pid, &st, 0) == -1) && - errno == EINTR) { // Better - /* nothing */ - } - -Curly braces ------------- - -Omit the curly braces around an ``if``, ``while``, ``for`` etc. -body only when both that body and the condition itself occupy a -single line. In every other case we require the braces. This -ensures that it is trivially easy to identify a -single-\ *statement* loop: each has only one *line* in its body. - -:: - - while (expr) // single line body; {} is forbidden - single_line_stmt(); - -:: - - while (expr(arg1, - arg2)) // indentation makes it obvious it is single line, - single_line_stmt(); // {} is optional (not enforced either way) - -:: - - while (expr1 && - expr2) { // multi-line, at same indentation, {} required - single_line_stmt(); - } - -However, the moment your loop/if/else body extends on to a second -line, for whatever reason (even if it's just an added comment), -then you should add braces. Otherwise, it would be too easy to -insert a statement just before that comment (without adding -braces), thinking it is already a multi-statement loop: - -:: - - while (true) // BAD! multi-line body with no braces - /* comment... */ - single_line_stmt(); - -Do this instead: - -:: - - while (true) { // Always put braces around a multi-line body. - /* comment... */ - single_line_stmt(); - } - -There is one exception: when the second body line is not at the -same indentation level as the first body line: - -:: - - if (expr) - die("a diagnostic that would make this line" - " extend past the 80-column limit")); - -It is safe to omit the braces in the code above, since the -further-indented second body line makes it obvious that this is -still a single-statement body. - -To reiterate, don't do this: - -:: - - if (expr) // BAD: no braces around... - while (expr_2) { // ... a multi-line body - ... - } - -Do this, instead: - -:: - - if (expr) { - while (expr_2) { - ... - } - } - -However, there is one exception in the other direction, when even -a one-line block should have braces. That occurs when that -one-line, brace-less block is an ``if`` or ``else`` block, and the -counterpart block **does** use braces. In that case, put braces -around both blocks. Also, if the ``else`` block is much shorter -than the ``if`` block, consider negating the ``if``-condition and -swapping the bodies, putting the short block first and making the -longer, multi-line block be the ``else`` block. - -:: - - if (expr) { - ... - ... - } - else - x = y; // BAD: braceless "else" with braced "then", - // and short block last - - if (expr) - x = y; // BAD: braceless "if" with braced "else" - else { - ... - ... - } - -Keeping braces consistent and putting the short block first is -preferred, especially when the multi-line body is more than a few -lines long, because it is easier to read and grasp the semantics -of an if-then-else block when the simpler block occurs first, -rather than after the more involved block: - -:: - - if (!expr) { - x = y; // putting the smaller block first is more readable - } else { - ... - ... - } - -But if negating a complex condition is too ugly, then at least add -braces: - -:: - - if (complex expr not worth negating) { - ... - ... - } else { - x = y; - } - -Use hanging braces for compound statements: the opening brace of a -compound statement should be on the same line as the condition -being tested. Only top-level function bodies, nested scopes, and -compound structure declarations should ever have { on a line by -itself. - -:: - - void - foo(int a, int b) - { // correct - function body - int 2d[][] = { - { // correct - complex initialization - 1, 2, - }, - }; - if (a) - { // BAD: compound brace on its own line - do_stuff(); - } - { // correct - nested scope - int tmp; - if (a < b) { // correct - hanging brace - tmp = b; - b = a; - a = tmp; - } - } - } - -Conditional expressions ------------------------ - -For readability reasons new code should avoid shortening -comparisons to 0 for numeric types. Boolean and pointer -comparisions may be shortened. All long forms are okay: - -:: - - virFooPtr foos = NULL; - size nfoos = 0; - bool hasFoos = false; - - GOOD: - if (!foos) - if (!hasFoos) - if (nfoos == 0) - if (foos == NULL) - if (hasFoos == true) - - BAD: - if (!nfoos) - if (nfoos) - -New code should avoid the ternary operator as much as possible. -Specifically it must never span more than one line or nest: - -:: - - BAD: - char *foo = baz ? - virDoSomethingReallyComplex(driver, vm, something, baz->foo) : - NULL; - - char *foo = bar ? bar->baz ? bar->baz->foo : "nobaz" : "nobar"; - -Preprocessor ------------- - -Macros defined with an ALL_CAPS name should generally be assumed -to be unsafe with regards to arguments with side-effects (that is, -MAX(a++, b--) might increment a or decrement b too many or too few -times). Exceptions to this rule are explicitly documented for -macros in viralloc.h and virstring.h. - -For variadic macros, stick with C99 syntax: - -:: - - #define vshPrint(_ctl, ...) fprintf(stdout, __VA_ARGS__) - -Use parenthesis when checking if a macro is defined, and use -indentation to track nesting: - -:: - - #if defined(HAVE_POSIX_FALLOCATE) && !defined(HAVE_FALLOCATE) - # define fallocate(a, ignored, b, c) posix_fallocate(a, b, c) - #endif - -C types -------- - -Use the right type. - -Scalars -^^^^^^^ - -- If you're using ``int`` or ``long``, odds are good that there's - a better type. -- If a variable is counting something, be sure to declare it with - an unsigned type. -- If it's memory-size-related, use ``size_t`` (use ``ssize_t`` - only if required). -- If it's file-size related, use uintmax_t, or maybe ``off_t``. -- If it's file-offset related (i.e., signed), use ``off_t``. -- If it's just counting small numbers use ``unsigned int``; (on - all but oddball embedded systems, you can assume that that type - is at least four bytes wide). -- If a variable has boolean semantics, give it the ``bool`` type - and use the corresponding ``true`` and ``false`` macros. -- In the unusual event that you require a specific width, use a - standard type like ``int32_t``, ``uint32_t``, ``uint64_t``, - etc. -- While using ``bool`` is good for readability, it comes with - minor caveats: - - - Don't use ``bool`` in places where the type size must be - constant across all systems, like public interfaces and - on-the-wire protocols. Note that it would be possible - (albeit wasteful) to use ``bool`` in libvirt's logical wire - protocol, since XDR maps that to its lower-level ``bool_t`` - type, which **is** fixed-size. - - Don't compare a bool variable against the literal, ``true``, - since a value with a logical non-false value need not be - ``1``. I.e., don't write ``if (seen == true) ...``. Rather, - write ``if (seen)...``. - -Of course, take all of the above with a grain of salt. If you're -about to use some system interface that requires a type like -``size_t``, ``pid_t`` or ``off_t``, use matching types for any -corresponding variables. - -Also, if you try to use e.g., ``unsigned int`` as a type, and that -conflicts with the signedness of a related variable, sometimes -it's best just to use the **wrong** type, if *pulling the thread* -and fixing all related variables would be too invasive. - -Finally, while using descriptive types is important, be careful -not to go overboard. If whatever you're doing causes warnings, or -requires casts, then reconsider or ask for help. - -Pointers -^^^^^^^^ - -Ensure that all of your pointers are *const-correct*. Unless a -pointer is used to modify the pointed-to storage, give it the -``const`` attribute. That way, the reader knows up-front that this -is a read-only pointer. Perhaps more importantly, if we're -diligent about this, when you see a non-const pointer, you're -guaranteed that it is used to modify the storage it points to, or -it is aliased to another pointer that is. - -Attribute annotations ---------------------- - -Use the following annotations to help the compiler and/or static -analysis tools understand the code better: - -+-------------------------------+------------------------------------------------------------+ -| Macro | Meaning | -+===============================+============================================================+ -| ``ATTRIBUTE_NONNULL`` | passing NULL for this parameter is not allowed | -+-------------------------------+------------------------------------------------------------+ -| ``ATTRIBUTE_PACKED`` | force a structure to be packed | -+-------------------------------+------------------------------------------------------------+ -| ``G_GNUC_FALLTHROUGH`` | allow code reuse by multiple switch cases | -+-------------------------------+------------------------------------------------------------+ -| ``G_GNUC_NO_INLINE`` | the function is mocked in the test suite | -+-------------------------------+------------------------------------------------------------+ -| ``G_GNUC_NORETURN`` | the function never returns | -+-------------------------------+------------------------------------------------------------+ -| ``G_GNUC_NULL_TERMINATED`` | last parameter must be NULL | -+-------------------------------+------------------------------------------------------------+ -| ``G_GNUC_PRINTF`` | validate that the formatting string matches parameters | -+-------------------------------+------------------------------------------------------------+ -| ``G_GNUC_UNUSED`` | parameter is unused in this implementation of the function | -+-------------------------------+------------------------------------------------------------+ -| ``G_GNUC_WARN_UNUSED_RESULT`` | the return value must be checked | -+-------------------------------+------------------------------------------------------------+ - -File handling -------------- - -Usage of the ``fdopen()``, ``close()``, ``fclose()`` APIs is -deprecated in libvirt code base to help avoiding double-closing of -files or file descriptors, which is particularly dangerous in a -multi-threaded application. Instead of these APIs, use the macros -from virfile.h - -- Open a file from a file descriptor: - - :: - - if ((file = VIR_FDOPEN(fd, "r")) == NULL) { - virReportSystemError(errno, "%s", - _("failed to open file from file descriptor")); - return -1; - } - /* fd is now invalid; only access the file using file variable */ - -- Close a file descriptor: - - :: - - if (VIR_CLOSE(fd) < 0) { - virReportSystemError(errno, "%s", _("failed to close file")); - } - -- Close a file: - - :: - - if (VIR_FCLOSE(file) < 0) { - virReportSystemError(errno, "%s", _("failed to close file")); - } - -- Close a file or file descriptor in an error path, without - losing the previous ``errno`` value: - - :: - - VIR_FORCE_CLOSE(fd); - VIR_FORCE_FCLOSE(file); - -String comparisons ------------------- - -Do not use the strcmp, strncmp, etc functions directly. Instead -use one of the following semantically named macros - -- For strict equality: - - :: - - STREQ(a,b) - STRNEQ(a,b) - -- For case insensitive equality: - - :: - - STRCASEEQ(a,b) - STRCASENEQ(a,b) - -- For strict equality of a substring: - - :: - - STREQLEN(a,b,n) - STRNEQLEN(a,b,n) - -- For case insensitive equality of a substring: - - :: - - STRCASEEQLEN(a,b,n) - STRCASENEQLEN(a,b,n) - -- For strict equality of a prefix: - - :: - - STRPREFIX(a,b) - -- To avoid having to check if a or b are NULL: - - :: - - STREQ_NULLABLE(a, b) - STRNEQ_NULLABLE(a, b) - -String copying --------------- - -Do not use the strncpy function. According to the man page, it -does **not** guarantee a NULL-terminated buffer, which makes it -extremely dangerous to use. Instead, use one of the replacement -functions provided by libvirt: - -:: - - virStrncpy(char *dest, const char *src, size_t n, size_t destbytes) - -The first two arguments have the same meaning as for strncpy, -namely the destination and source of the copy operation. Unlike -strncpy, the function will always copy exactly the number of bytes -requested and make sure the destination is NULL-terminated, as the -source is required to be; sanity checks are performed to ensure -the size of the destination, as specified by the last argument, is -sufficient for the operation to succeed. On success, 0 is -returned; on failure, a value <0 is returned instead. - -:: - - virStrcpy(char *dest, const char *src, size_t destbytes) - -Use this variant if you know you want to copy the entire src -string into dest. - -:: - - virStrcpyStatic(char *dest, const char *src) - -Use this variant if you know you want to copy the entire src -string into dest **and** you know that your destination string is -a static string (i.e. that sizeof(dest) returns something -meaningful). Note that this is a macro, so arguments could be -evaluated more than once. - -:: - - dst = g_strdup(src); - dst = g_strndup(src, n); - -You should avoid using strdup or strndup directly as they do not -handle out-of-memory errors, and do not allow a NULL source. Use -``g_strdup`` and ``g_strndup`` from GLib which abort on OOM and -handle NULL source by returning NULL. - -Variable length string buffer ------------------------------ - -If there is a need for complex string concatenations, avoid using -the usual sequence of malloc/strcpy/strcat/snprintf functions and -make use of either the -`GString <https://developer.gnome.org/glib/stable/glib-Strings.html>`__ -type from GLib or the virBuffer API. If formatting XML or QEMU -command line is needed, use the virBuffer API described in -virbuffer.h, since it has helper functions for those. - -Typical usage is as follows: - -:: - - char * - somefunction(...) - { - g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER; - - ... - - virBufferAddLit(&buf, "<domain>\n"); - - ... - - if (some_error) - return NULL; /* g_auto will free the memory used so far */ - - ... - - virBufferAddLit(&buf, "</domain>\n"); - - ... - - if (virBufferCheckError(&buf) < 0) - return NULL; - - return virBufferContentAndReset(&buf); - } - -Include files -------------- - -There are now quite a large number of include files, both libvirt -internal and external, and system includes. To manage all this -complexity it's best to stick to the following general plan for -all \*.c source files: - -:: - - /* - * Copyright notice - * .... - * .... - * .... - * - */ - - #include <config.h> Must come first in every file. - - #include <stdio.h> Any system includes you need. - #include <string.h> - #include <limits.h> - - #if WITH_NUMACTL Some system includes aren't supported - # include <numa.h> everywhere so need these #if guards. - #endif - - #include "internal.h" Include this first, after system includes. - - #include "util.h" Any libvirt internal header files. - #include "buf.h" - - static int - myInternalFunc() The actual code. - { - ... - -Of particular note: **Do not** include libvirt/libvirt.h, -libvirt/virterror.h, libvirt/libvirt-qemu.h, or -libvirt/libvirt-lxc.h. They are included by "internal.h" already -and there are some special reasons why you cannot include these -files explicitly. One of the special cases, "libvirt/libvirt.h" is -included prior to "internal.h" in "remote_protocol.x", to avoid -exposing \*_LAST enum elements. - -Printf-style functions ----------------------- - -Whenever you add a new printf-style function, i.e., one with a -format string argument and following "..." in its prototype, be -sure to use gcc's printf attribute directive in the prototype. For -example, here's the one for virCommandAddEnvFormat in -vircommand.h: - -:: - - void virCommandAddEnvFormat(virCommandPtr cmd, const char *format, ...) - G_GNUC_PRINTF(2, 3); - -This makes it so gcc's -Wformat and -Wformat-security options can -do their jobs and cross-check format strings with the number and -types of arguments. - -When printing to a string, consider using GString or virBuffer for -incremental allocations, g_strdup_printf for a one-shot -allocation, and g_snprintf for fixed-width buffers. Only use -g_sprintf, if you can prove the buffer won't overflow. - -Error message format --------------------- - -Error messages visible to the user should be short and -descriptive. All error messages are translated using gettext and -thus must be wrapped in ``_()`` macro. To simplify the translation -work, the error message must not be concatenated from various -parts. To simplify searching for the error message in the code the -strings should not be broken even if they result into a line -longer than 80 columns and any formatting modifier should be -enclosed by quotes or other obvious separator. If a string used -with ``%s`` can be NULL the NULLSTR macro must be used. - -:: - - GOOD: virReportError(VIR_ERR_INTERNAL_ERROR, - _("Failed to connect to remote host '%s'"), hostname) - - BAD: virReportError(VIR_ERR_INTERNAL_ERROR, - _("Failed to %s to remote host '%s'"), - "connect", hostname); - - BAD: virReportError(VIR_ERR_INTERNAL_ERROR, - _("Failed to connect " - "to remote host '%s'), - hostname); - -Use of goto ------------ - -The use of goto is not forbidden, and goto is widely used -throughout libvirt. While the uncontrolled use of goto will -quickly lead to unmaintainable code, there is a place for it in -well structured code where its use increases readability and -maintainability. In general, if goto is used for error recovery, -it's likely to be ok, otherwise, be cautious or avoid it all -together. - -The typical use of goto is to jump to cleanup code in the case of -a long list of actions, any of which may fail and cause the entire -operation to fail. In this case, a function will have a single -label at the end of the function. It's almost always ok to use -this style. In particular, if the cleanup code only involves -free'ing memory, then having multiple labels is overkill. g_free() -and most of the functions named XXXFree() in libvirt is required -to handle NULL as its arg. This does not apply to libvirt's public -APIs. Thus you can safely call free on all the variables even if -they were not yet allocated (yes they have to have been -initialized to NULL). This is much simpler and clearer than having -multiple labels. Note that most of libvirt's type declarations can -be marked with either ``g_autofree`` or ``g_autoptr`` which uses -the compiler's ``__attribute__((cleanup))`` that calls the -appropriate free function when the variable goes out of scope. - -There are a couple of signs that a particular use of goto is not -ok: - -- You're using multiple labels. If you find yourself using - multiple labels, you're strongly encouraged to rework your code - to eliminate all but one of them. -- The goto jumps back up to a point above the current line of - code being executed. Please use some combination of looping - constructs to re-execute code instead; it's almost certainly - going to be more understandable by others. One well-known - exception to this rule is restarting an i/o operation following - EINTR. -- The goto jumps down to an arbitrary place in the middle of a - function followed by further potentially failing calls. You - should almost certainly be using a conditional and a block - instead of a goto. Perhaps some of your function's logic would - be better pulled out into a helper function. - -Although libvirt does not encourage the Linux kernel wind/unwind -style of multiple labels, there's a good general discussion of the -issue archived at -`KernelTrap <http://kerneltrap.org/node/553/2131>`__ - -When using goto, please use one of these standard labels if it -makes sense: - -:: - - error: A path only taken upon return with an error code - cleanup: A path taken upon return with success code + optional error - no_memory: A path only taken upon return with an OOM error code - retry: If needing to jump upwards (e.g., retry on EINTR) - -Top-level labels should be indented by one space (putting them on -the beginning of the line confuses function context detection in -git): - -:: - - int foo() - { - /* ... do stuff ... */ - cleanup: - /* ... do other stuff ... */ - } - Libvirt committer guidelines ============================ -- 2.25.1
Most new contributors are probably going to modify existing code rather than introducing all-new programs and scripts, and even when the latter happen they'll hopefully get a feel for which programming languages are considered acceptable for the project by looking at what's already in the repo. Make this part less prominent by moving it to a separate page. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/hacking.rst | 21 --------------------- docs/programming-languages.rst | 21 +++++++++++++++++++++ 2 files changed, 21 insertions(+), 21 deletions(-) create mode 100644 docs/programming-languages.rst diff --git a/docs/hacking.rst b/docs/hacking.rst index 356dbc506b..89f8f412c1 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -322,27 +322,6 @@ background reading on the subject, on `Richard Jones' guide to working with open source projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. -Language Usage -============== - -The libvirt repository makes use of a large number of programming -languages. It is anticipated that in the future libvirt will adopt -use of other new languages. To reduce the overall burden on -developers, there is thus a general desire to phase out usage of -some of the existing languages. - -The preferred languages at this time are: - -- C - for the main libvirt codebase. Dialect supported by - GCC/CLang only. -- Python - for supporting build scripts / tools. Code must run - with both version 2.7 and 3.x at this time. - -Languages that should not be used for any new contributions: - -- Perl - build scripts must be written in Python instead. -- Shell - build scripts must be written in Python instead. - Tooling ======= diff --git a/docs/programming-languages.rst b/docs/programming-languages.rst new file mode 100644 index 0000000000..9d7dbdcd37 --- /dev/null +++ b/docs/programming-languages.rst @@ -0,0 +1,21 @@ +===================== +Programming languages +===================== + +The libvirt repository makes use of a large number of programming +languages. It is anticipated that in the future libvirt will adopt +use of other new languages. To reduce the overall burden on +developers, there is thus a general desire to phase out usage of +some of the existing languages. + +The preferred languages at this time are: + +- C - for the main libvirt codebase. Dialect supported by + GCC/CLang only. +- Python - for supporting build scripts / tools. Code must run + with both version 2.7 and 3.x at this time. + +Languages that should not be used for any new contributions: + +- Perl - build scripts must be written in Python instead. +- Shell - build scripts must be written in Python instead. -- 2.25.1
This part describes entirely optional tooling, so it makes sense not to have it advertised too prominently. Move it to a separate page. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/developer-tooling.rst | 13 +++++++++++++ docs/hacking.rst | 13 ------------- 2 files changed, 13 insertions(+), 13 deletions(-) create mode 100644 docs/developer-tooling.rst diff --git a/docs/developer-tooling.rst b/docs/developer-tooling.rst new file mode 100644 index 0000000000..c8980e3e4f --- /dev/null +++ b/docs/developer-tooling.rst @@ -0,0 +1,13 @@ +================= +Developer tooling +================= + +libvirt includes support for some useful development tools right +in its source repository, meaning users will be able to take +advantage of them without little or no configuration. Examples +include: + +- `color_coded <https://github.com/jeaye/color_coded>`__, a vim + plugin for libclang-powered semantic syntax highlighting; +- `YouCompleteMe <http://valloric.github.io/YouCompleteMe/>`__, a + vim plugin for libclang-powered semantic code completion. diff --git a/docs/hacking.rst b/docs/hacking.rst index 89f8f412c1..35c246bf26 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -322,19 +322,6 @@ background reading on the subject, on `Richard Jones' guide to working with open source projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. -Tooling -======= - -libvirt includes support for some useful development tools right -in its source repository, meaning users will be able to take -advantage of them without little or no configuration. Examples -include: - -- `color_coded <https://github.com/jeaye/color_coded>`__, a vim - plugin for libclang-powered semantic syntax highlighting; -- `YouCompleteMe <http://valloric.github.io/YouCompleteMe/>`__, a - vim plugin for libclang-powered semantic code completion. - Libvirt committer guidelines ============================ -- 2.25.1
While it's good to have these rules written down for reference, they apply exclusively to committers, who by definition are familiar with the project and probably work on it daily, so there's no need to have them front and center when a separate page will do. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/committer-guidelines.rst | 33 +++++++++++++++++++++++++++++++++ docs/hacking.rst | 33 --------------------------------- 2 files changed, 33 insertions(+), 33 deletions(-) create mode 100644 docs/committer-guidelines.rst diff --git a/docs/committer-guidelines.rst b/docs/committer-guidelines.rst new file mode 100644 index 0000000000..3be08e6fed --- /dev/null +++ b/docs/committer-guidelines.rst @@ -0,0 +1,33 @@ +==================== +Committer guidelines +==================== + +The AUTHORS files indicates the list of people with commit access +right who can actually merge the patches. + +The general rule for committing a patch is to make sure it has +been reviewed properly in the mailing-list first, usually if a +couple of people gave an ACK or +1 to a patch and nobody raised an +objection on the list it should be good to go. If the patch +touches a part of the code where you're not the main maintainer, +or where you do not have a very clear idea of how things work, +it's better to wait for a more authoritative feedback though. +Before committing, please also rebuild locally, run 'make check +syntax-check', and make sure you don't raise errors. + +An exception to 'review and approval on the list first' is fixing +failures to build: + +- if a recently committed patch breaks compilation on a platform + or for a given driver, then it's fine to commit a minimal fix + directly without getting the review feedback first +- if make check or make syntax-check breaks, if there is an + obvious fix, it's fine to commit immediately. The patch should + still be sent to the list (or tell what the fix was if + trivial), and 'make check syntax-check' should pass too, before + committing anything +- fixes for documentation and code comments can be managed in the + same way, but still make sure they get reviewed if non-trivial. +- (ir)regular pulls from other repositories or automated updates, + such as the keycodemap submodule updates, pulling in new + translations or updating the container images for the CI system diff --git a/docs/hacking.rst b/docs/hacking.rst index 35c246bf26..39e303c103 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -321,36 +321,3 @@ There is more on this subject, including lots of links to background reading on the subject, on `Richard Jones' guide to working with open source projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. - -Libvirt committer guidelines -============================ - -The AUTHORS files indicates the list of people with commit access -right who can actually merge the patches. - -The general rule for committing a patch is to make sure it has -been reviewed properly in the mailing-list first, usually if a -couple of people gave an ACK or +1 to a patch and nobody raised an -objection on the list it should be good to go. If the patch -touches a part of the code where you're not the main maintainer, -or where you do not have a very clear idea of how things work, -it's better to wait for a more authoritative feedback though. -Before committing, please also rebuild locally, run 'make check -syntax-check', and make sure you don't raise errors. - -An exception to 'review and approval on the list first' is fixing -failures to build: - -- if a recently committed patch breaks compilation on a platform - or for a given driver, then it's fine to commit a minimal fix - directly without getting the review feedback first -- if make check or make syntax-check breaks, if there is an - obvious fix, it's fine to commit immediately. The patch should - still be sent to the list (or tell what the fix was if - trivial), and 'make check syntax-check' should pass too, before - committing anything -- fixes for documentation and code comments can be managed in the - same way, but still make sure they get reviewed if non-trivial. -- (ir)regular pulls from other repositories or automated updates, - such as the keycodemap submodule updates, pulling in new - translations or updating the container images for the CI system -- 2.25.1
This part contains a lot of useful tips, but presenting all of them at the same time obfuscated the central message which is, 'make check' and 'make syntax-check' must pass after each patch in a series. Let's move them to a separate page. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- build-aux/syntax-check.mk | 2 +- docs/advanced-tests.rst | 178 ++++++++++++++++++++++++++++++++++++++ docs/hacking.rst | 159 ---------------------------------- 3 files changed, 179 insertions(+), 160 deletions(-) create mode 100644 docs/advanced-tests.rst diff --git a/build-aux/syntax-check.mk b/build-aux/syntax-check.mk index 8bee1bbbf1..cbcdf445aa 100644 --- a/build-aux/syntax-check.mk +++ b/build-aux/syntax-check.mk @@ -2040,7 +2040,7 @@ exclude_file_name_regexp--sc_prohibit_canonicalize_file_name = \ ^(build-aux/syntax-check\.mk|tests/virfilemock\.c)$$ exclude_file_name_regexp--sc_prohibit_raw_allocation = \ - ^(docs/hacking\.rst|src/util/viralloc\.[ch]|examples/.*|tests/(securityselinuxhelper|(vircgroup|nss)mock|commandhelper)\.c|tools/wireshark/src/packet-libvirt\.c|tools/nss/libvirt_nss(_leases|_macs)?\.c|build-aux/useless-if-before-free)$$ + ^(docs/advanced-tests\.rst|src/util/viralloc\.[ch]|examples/.*|tests/(securityselinuxhelper|(vircgroup|nss)mock|commandhelper)\.c|tools/wireshark/src/packet-libvirt\.c|tools/nss/libvirt_nss(_leases|_macs)?\.c|build-aux/useless-if-before-free)$$ exclude_file_name_regexp--sc_prohibit_readlink = \ ^src/(util/virutil|lxc/lxc_container)\.c$$ diff --git a/docs/advanced-tests.rst b/docs/advanced-tests.rst new file mode 100644 index 0000000000..d2d29d976d --- /dev/null +++ b/docs/advanced-tests.rst @@ -0,0 +1,178 @@ +========================= +Advanced test suite usage +========================= + +The basic requirement before submitting changes to libvirt is that + +:: + + $ make check + $ make syntax-check + +succeed after each commit. + +The libvirt test suite, however, support additional features: for +example, it's possible to look for memory leaks and similar issues +by running + +:: + + $ make -C tests valgrind + +`Valgrind <http://valgrind.org/>`__ is a test that checks for +memory management issues, such as leaks or use of uninitialized +variables. + +Some tests are skipped by default in a development environment, +based on the time they take in comparison to the likelihood +that those tests will turn up problems during incremental +builds. These tests default to being run when building from a +tarball or with the configure option --enable-expensive-tests; +you can also force a one-time toggle of these tests by setting +VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in: + +:: + + $ make check VIR_TEST_EXPENSIVE=1 + +If you encounter any failing tests, the VIR_TEST_DEBUG +environment variable may provide extra information to debug the +failures. Larger values of VIR_TEST_DEBUG may provide larger +amounts of information: + +:: + + $ VIR_TEST_DEBUG=1 make check (or) + $ VIR_TEST_DEBUG=2 make check + +When debugging failures during development, it is possible to +focus in on just the failing subtests by using VIR_TEST_RANGE. +I.e. to run all tests from 3 to 20 with the exception of tests +6 and 16, use: + +:: + + $ VIR_TEST_DEBUG=1 VIR_TEST_RANGE=3-5,7-20,^16 ./run tests/qemuxml2argvtest + +Also, individual tests can be run from inside the ``tests/`` +directory, like: + +:: + + $ ./qemuxml2xmltest + +If you are adding new test cases, or making changes that alter +existing test output, you can use the environment variable +VIR_TEST_REGENERATE_OUTPUT to quickly update the saved test +data. Of course you still need to review the changes VERY +CAREFULLY to ensure they are correct. + +:: + + $ VIR_TEST_REGENERATE_OUTPUT=1 ./qemuxml2argvtest + +There is also a ``./run`` script at the top level, to make it +easier to run programs that have not yet been installed, as +well as to wrap invocations of various tests under gdb or +Valgrind. + +When running our test suite it may happen that the test result +is nondeterministic because of the test suite relying on a +particular file in the system being accessible or having some +specific value. To catch this kind of errors, the test suite +has a module for that prints any path touched that fulfils +constraints described above into a file. To enable it just set +``VIR_TEST_FILE_ACCESS`` environment variable. Then +``VIR_TEST_FILE_ACCESS_OUTPUT`` environment variable can alter +location where the file is stored. + +:: + + $ VIR_TEST_FILE_ACCESS=1 VIR_TEST_FILE_ACCESS_OUTPUT="/tmp/file_access.txt" ./qemuxml2argvtest + +#. The Valgrind test should produce similar output to +``make check``. If the output has traces within libvirt API's, +then investigation is required in order to determine the cause +of the issue. Output such as the following indicates some sort +of leak: + +:: + + ==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89 + ==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270) + ==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8) + ==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410) + ==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188) + ==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640) + ==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590) + ==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100) + ==5414== by 0x41E20F: virtTestRun (testutils.c:161) + ==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866) + ==5414== by 0x41E84A: virtTestMain (testutils.c:723) + ==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so) + +In this example, the ``virDomainDefParseXML()`` had an error +path where the ``virDomainVideoDefPtr video`` pointer was not +properly disposed. By simply adding a +``virDomainVideoDefFree(video);`` in the error path, the issue +was resolved. + +Another common mistake is calling a printing function, such as +``VIR_DEBUG()`` without initializing a variable to be printed. +The following example involved a call which could return an +error, but not set variables passed by reference to the call. +The solution was to initialize the variables prior to the call. + +:: + + ==4749== Use of uninitialised value of size 8 + ==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so) + ==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so) + ==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so) + ==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199) + ==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814) + ==4749== by 0x4C8AA96: virLogMessage (virlog.c:751) + ==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225) + ==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439) + ==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562) + ==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927) + ==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467) + ==4749== by 0x40AB8F: virtTestRun (testutils.c:161) + +Valgrind will also find some false positives or code paths +which cannot be resolved by making changes to the libvirt code. +For these paths, it is possible to add a filter to avoid the +errors. For example: + +:: + + ==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20 + ==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270) + ==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so) + ==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1) + ==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1) + ==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so) + ==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so) + ==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so) + +In this instance, it is acceptable to modify the +``tests/.valgrind.supp`` file in order to add a suppression +filter. The filter should be unique enough to not suppress real +leaks, but it should be generic enough to cover multiple code +paths. The format of the entry can be found in the +documentation found at the `Valgrind home +page <http://valgrind.org/>`__. The following trace was added +to ``tests/.valgrind.supp`` in order to suppress the warning: + +:: + + { + dlInitMemoryLeak1 + Memcheck:Leak + fun:?alloc + ... + fun:call_init.part.0 + fun:_dl_init + ... + obj:*/lib*/ld-2.*so* + } diff --git a/docs/hacking.rst b/docs/hacking.rst index 39e303c103..bf01c05928 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -145,165 +145,6 @@ General tips for contributing patches make check make syntax-check - make -C tests valgrind - - `Valgrind <http://valgrind.org/>`__ is a test that checks for - memory management issues, such as leaks or use of uninitialized - variables. - - Some tests are skipped by default in a development environment, - based on the time they take in comparison to the likelihood - that those tests will turn up problems during incremental - builds. These tests default to being run when building from a - tarball or with the configure option --enable-expensive-tests; - you can also force a one-time toggle of these tests by setting - VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in: - - :: - - make check VIR_TEST_EXPENSIVE=1 - - If you encounter any failing tests, the VIR_TEST_DEBUG - environment variable may provide extra information to debug the - failures. Larger values of VIR_TEST_DEBUG may provide larger - amounts of information: - - :: - - VIR_TEST_DEBUG=1 make check (or) - VIR_TEST_DEBUG=2 make check - - When debugging failures during development, it is possible to - focus in on just the failing subtests by using VIR_TEST_RANGE. - I.e. to run all tests from 3 to 20 with the exception of tests - 6 and 16, use: - - :: - - VIR_TEST_DEBUG=1 VIR_TEST_RANGE=3-5,7-20,^16 ./run tests/qemuxml2argvtest - - Also, individual tests can be run from inside the ``tests/`` - directory, like: - - :: - - ./qemuxml2xmltest - - If you are adding new test cases, or making changes that alter - existing test output, you can use the environment variable - VIR_TEST_REGENERATE_OUTPUT to quickly update the saved test - data. Of course you still need to review the changes VERY - CAREFULLY to ensure they are correct. - - :: - - VIR_TEST_REGENERATE_OUTPUT=1 ./qemuxml2argvtest - - There is also a ``./run`` script at the top level, to make it - easier to run programs that have not yet been installed, as - well as to wrap invocations of various tests under gdb or - Valgrind. - - When running our test suite it may happen that the test result - is nondeterministic because of the test suite relying on a - particular file in the system being accessible or having some - specific value. To catch this kind of errors, the test suite - has a module for that prints any path touched that fulfils - constraints described above into a file. To enable it just set - ``VIR_TEST_FILE_ACCESS`` environment variable. Then - ``VIR_TEST_FILE_ACCESS_OUTPUT`` environment variable can alter - location where the file is stored. - - :: - - VIR_TEST_FILE_ACCESS=1 VIR_TEST_FILE_ACCESS_OUTPUT="/tmp/file_access.txt" ./qemuxml2argvtest - -#. The Valgrind test should produce similar output to - ``make check``. If the output has traces within libvirt API's, - then investigation is required in order to determine the cause - of the issue. Output such as the following indicates some sort - of leak: - - :: - - ==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89 - ==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270) - ==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8) - ==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410) - ==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188) - ==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640) - ==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590) - ==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100) - ==5414== by 0x41E20F: virtTestRun (testutils.c:161) - ==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866) - ==5414== by 0x41E84A: virtTestMain (testutils.c:723) - ==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so) - - In this example, the ``virDomainDefParseXML()`` had an error - path where the ``virDomainVideoDefPtr video`` pointer was not - properly disposed. By simply adding a - ``virDomainVideoDefFree(video);`` in the error path, the issue - was resolved. - - Another common mistake is calling a printing function, such as - ``VIR_DEBUG()`` without initializing a variable to be printed. - The following example involved a call which could return an - error, but not set variables passed by reference to the call. - The solution was to initialize the variables prior to the call. - - :: - - ==4749== Use of uninitialised value of size 8 - ==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so) - ==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so) - ==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so) - ==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199) - ==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814) - ==4749== by 0x4C8AA96: virLogMessage (virlog.c:751) - ==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225) - ==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439) - ==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562) - ==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927) - ==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467) - ==4749== by 0x40AB8F: virtTestRun (testutils.c:161) - - Valgrind will also find some false positives or code paths - which cannot be resolved by making changes to the libvirt code. - For these paths, it is possible to add a filter to avoid the - errors. For example: - - :: - - ==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20 - ==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270) - ==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so) - ==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1) - ==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1) - ==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so) - ==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so) - ==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so) - - In this instance, it is acceptable to modify the - ``tests/.valgrind.supp`` file in order to add a suppression - filter. The filter should be unique enough to not suppress real - leaks, but it should be generic enough to cover multiple code - paths. The format of the entry can be found in the - documentation found at the `Valgrind home - page <http://valgrind.org/>`__. The following trace was added - to ``tests/.valgrind.supp`` in order to suppress the warning: - - :: - - { - dlInitMemoryLeak1 - Memcheck:Leak - fun:?alloc - ... - fun:call_init.part.0 - fun:_dl_init - ... - obj:*/lib*/ld-2.*so* - } #. Update tests and/or documentation, particularly if you are adding a new feature or changing the output of a program. -- 2.25.1
This is a relatively lengthy part with lots of details, which many people who are familiar with a mail-based development workflow will already know and which will become obsolete once we move to GitLab. Move the contents to a separate page. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/hacking.rst | 85 ----------------------------------- docs/submitting-patches.rst | 88 +++++++++++++++++++++++++++++++++++++ 2 files changed, 88 insertions(+), 85 deletions(-) create mode 100644 docs/submitting-patches.rst diff --git a/docs/hacking.rst b/docs/hacking.rst index bf01c05928..abede5f206 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -21,91 +21,6 @@ General tips for contributing patches The libvirt release process automatically pulls the latest version of each translation file from zanata. -#. The simplest way to send patches is to use the - `git-publish <https://github.com/stefanha/git-publish>`__ - tool. All libvirt-related repositories contain a config file - that tells git-publish to use the correct mailing list and - subject prefix. - - Alternatively, you may send patches using ``git send-email``. - - Also, for code motion patches, you may find that - ``git diff --patience`` provides an easier-to-read - patch. However, the usual workflow of libvirt developer is: - - :: - - git checkout master - git pull - git checkout -t origin -b workbranch - Hack, committing any changes along the way - - More hints on compiling can be found `here <compiling.html>`__. - When you want to post your patches: - - :: - - git pull --rebase - (fix any conflicts) - git send-email --cover-letter --no-chain-reply-to --annotate \ - --confirm=always --to=libvir-list@redhat.com master - - For a single patch you can omit ``--cover-letter``, but a - series of two or more patches needs a cover letter. - - Note that the ``git send-email`` subcommand may not be in the - main git package and using it may require installation of a - separate package, for example the "git-email" package in Fedora - and Debian. If this is your first time using - ``git send-email``, you might need to configure it to point it - to your SMTP server with something like: - - :: - - git config --global sendemail.smtpServer stmp.youremailprovider.net - - If you get tired of typing ``--to=libvir-list@redhat.com`` all - the time, you can configure that to be automatically handled as - well: - - :: - - git config sendemail.to libvir-list@redhat.com - - As a rule, patches should be sent to the mailing list only: all - developers are subscribed to libvir-list and read it regularly, - so **please don't CC individual developers** unless they've - explicitly asked you to. - - Avoid using mail clients for sending patches, as most of them - will mangle the messages in some way, making them unusable for - our purposes. Gmail and other Web-based mail clients are - particularly bad at this. - - If everything went well, your patch should show up on the - `libvir-list - archives <https://www.redhat.com/archives/libvir-list/>`__ in a - matter of minutes; if you still can't find it on there after an - hour or so, you should double-check your setup. **Note that, if - you are not already a subscriber, your very first post to the - mailing list will be subject to moderation**, and it's not - uncommon for that to take around a day. - - Please follow this as close as you can, especially the rebase - and ``git send-email`` part, as it makes life easier for other - developers to review your patch set. - - One should avoid sending patches as attachments, but rather - send them in email body along with commit message. If a - developer is sending another version of the patch (e.g. to - address review comments), they are advised to note differences - to previous versions after the ``---`` line in the patch so - that it helps reviewers but doesn't become part of git history. - Moreover, such patch needs to be prefixed correctly with - ``--subject-prefix=PATCHv2`` appended to - ``git send-email`` (substitute ``v2`` with the - correct version if needed though). - #. In your commit message, make the summary line reasonably short (60 characters is typical), followed by a blank line, followed by any longer description of why your patch makes sense. If the diff --git a/docs/submitting-patches.rst b/docs/submitting-patches.rst new file mode 100644 index 0000000000..17b072655d --- /dev/null +++ b/docs/submitting-patches.rst @@ -0,0 +1,88 @@ +================== +Submitting patches +================== + +The simplest way to send patches is to use the +`git-publish <https://github.com/stefanha/git-publish>`__ +tool. All libvirt-related repositories contain a config file +that tells git-publish to use the correct mailing list and +subject prefix. + +Alternatively, you may send patches using ``git send-email``. + +Also, for code motion patches, you may find that +``git diff --patience`` provides an easier-to-read +patch. However, the usual workflow of libvirt developer is: + +:: + + $ git checkout master + $ git pull + $ git checkout -t origin -b workbranch + (hack, committing any changes along the way) + +More hints on compiling can be found `here <compiling.html>`__. +When you want to post your patches: + +:: + + $ git pull --rebase + (fix any conflicts) + $ git send-email --cover-letter --no-chain-reply-to --annotate \ + --confirm=always --to=libvir-list@redhat.com master + +For a single patch you can omit ``--cover-letter``, but a +series of two or more patches needs a cover letter. + +Note that the ``git send-email`` subcommand may not be in the +main git package and using it may require installation of a +separate package, for example the "git-email" package in Fedora +and Debian. If this is your first time using +``git send-email``, you might need to configure it to point it +to your SMTP server with something like: + +:: + + $ git config --global sendemail.smtpServer stmp.youremailprovider.net + +If you get tired of typing ``--to=libvir-list@redhat.com`` all +the time, you can configure that to be automatically handled as +well: + +:: + + $ git config sendemail.to libvir-list@redhat.com + +As a rule, patches should be sent to the mailing list only: all +developers are subscribed to libvir-list and read it regularly, +so **please don't CC individual developers** unless they've +explicitly asked you to. + +Avoid using mail clients for sending patches, as most of them +will mangle the messages in some way, making them unusable for +our purposes. Gmail and other Web-based mail clients are +particularly bad at this. + +If everything went well, your patch should show up on the +`libvir-list +archives <https://www.redhat.com/archives/libvir-list/>`__ in a +matter of minutes; if you still can't find it on there after an +hour or so, you should double-check your setup. **Note that, if +you are not already a subscriber, your very first post to the +mailing list will be subject to moderation**, and it's not +uncommon for that to take around a day. + +Please follow this as close as you can, especially the rebase +and ``git send-email`` part, as it makes life easier for other +developers to review your patch set. + +One should avoid sending patches as attachments, but rather +send them in email body along with commit message. If a +developer is sending another version of the patch (e.g. to +address review comments), they are advised to note differences +to previous versions after the ``---`` line in the patch so +that it helps reviewers but doesn't become part of git history. +Moreover, such patch needs to be prefixed correctly with +``--subject-prefix=PATCHv2`` appended to +``git send-email`` (substitute ``v2`` with the +correct version if needed though). -- 2.25.1
These guidelines should already be familiar to people who have contributed to other open source projects, so it doesn't make much sense for them to be so prominent. Move them to a separate page. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/best-practices.rst | 37 +++++++++++++++++++++++++++++++++++++ docs/hacking.rst | 29 ----------------------------- 2 files changed, 37 insertions(+), 29 deletions(-) create mode 100644 docs/best-practices.rst diff --git a/docs/best-practices.rst b/docs/best-practices.rst new file mode 100644 index 0000000000..7c48ff10be --- /dev/null +++ b/docs/best-practices.rst @@ -0,0 +1,37 @@ +============== +Best practices +============== + +These are a few guidelines to keep in mind when submitting patches +to libvirt: following them will maximise the chance of your patches +being reviewed in a timely manner and being accepted into libvirt +with minimal back-and-forth. + +- Discuss any large changes on the mailing list first. Post + patches early and listen to feedback. + +- In your commit message, make the summary line reasonably short + (60 characters is typical), followed by a blank line, followed + by any longer description of why your patch makes sense. If the + patch fixes a regression, and you know what commit introduced + the problem, mentioning that is useful. If the patch resolves a + bugzilla report, mentioning the URL of the bug number is + useful; but also summarize the issue rather than making all + readers follow the link. You can use 'git shortlog -30' to get + an idea of typical summary lines. + +- Split large changes into a series of smaller patches, + self-contained if possible, with an explanation of each patch + and an explanation of how the sequence of patches fits + together. Moreover, please keep in mind that it's required to + be able to compile cleanly (**including** + ``make check`` and ``make syntax-check``) after each + patch. A feature does not have to work until the end of a + series, but intermediate patches must compile and not cause + test-suite failures (this is to preserve the usefulness of + ``git bisect``, among other things). + +There is more on this subject, including lots of links to +background reading on the subject, on `Richard Jones' guide to +working with open source +projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. diff --git a/docs/hacking.rst b/docs/hacking.rst index abede5f206..996999885e 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -7,9 +7,6 @@ Contributor guidelines General tips for contributing patches ===================================== -#. Discuss any large changes on the mailing list first. Post - patches early and listen to feedback. - #. Official upstream repository is kept in git (``https://libvirt.org/git/libvirt.git``) and is browsable along with other libvirt-related repositories (e.g. @@ -21,16 +18,6 @@ General tips for contributing patches The libvirt release process automatically pulls the latest version of each translation file from zanata. -#. In your commit message, make the summary line reasonably short - (60 characters is typical), followed by a blank line, followed - by any longer description of why your patch makes sense. If the - patch fixes a regression, and you know what commit introduced - the problem, mentioning that is useful. If the patch resolves a - bugzilla report, mentioning the URL of the bug number is - useful; but also summarize the issue rather than making all - readers follow the link. You can use 'git shortlog -30' to get - an idea of typical summary lines. - #. Contributors to libvirt projects **must** assert that they are in compliance with the `Developer Certificate of Origin 1.1 <https://developercertificate.org/>`__. This is achieved by @@ -39,17 +26,6 @@ General tips for contributing patches attests that the contributor has read the above lined DCO and agrees with its statements. -#. Split large changes into a series of smaller patches, - self-contained if possible, with an explanation of each patch - and an explanation of how the sequence of patches fits - together. Moreover, please keep in mind that it's required to - be able to compile cleanly (**including** - ``make check`` and ``make syntax-check``) after each - patch. A feature does not have to work until the end of a - series, but intermediate patches must compile and not cause - test-suite failures (this is to preserve the usefulness of - ``git bisect``, among other things). - #. Make sure your patches apply against libvirt GIT. Developers only follow GIT and don't care much about released versions. @@ -72,8 +48,3 @@ General tips for contributing patches libvirt developers, such as code refactoring, don't belong in the release notes. Note that ``docs/news.xml`` should be updated in its own commit not to get in the way of backports. - -There is more on this subject, including lots of links to -background reading on the subject, on `Richard Jones' guide to -working with open source -projects <http://people.redhat.com/rjones/how-to-supply-code-to-open-source-projects/>`__. -- 2.25.1
This organizes the existing contents into sections, tweaks some parts a bit and adds links to the pages where the contents that were ripped out of hacking.rst now live, either inline or in the catch-all "further reading" section depending on what makes more sense. The result is that it's now possible to consume this page, which is the entry point for new contributors, in just a few minutes, and then drill down further based on factors such as the familiarity with the open source development model or mail-based workflows. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- docs/hacking.rst | 129 +++++++++++++++++++++++++++++------------------ 1 file changed, 79 insertions(+), 50 deletions(-) diff --git a/docs/hacking.rst b/docs/hacking.rst index 996999885e..1c64146c5d 100644 --- a/docs/hacking.rst +++ b/docs/hacking.rst @@ -1,50 +1,79 @@ -====================== -Contributor guidelines -====================== - -.. contents:: - -General tips for contributing patches -===================================== - -#. Official upstream repository is kept in git - (``https://libvirt.org/git/libvirt.git``) and is browsable - along with other libvirt-related repositories (e.g. - libvirt-python) `online <https://libvirt.org/git/>`__. - -#. Patches to translations are maintained via the `zanata - project <https://fedora.zanata.org/>`__. If you want to fix a - translation in a .po file, join the appropriate language team. - The libvirt release process automatically pulls the latest - version of each translation file from zanata. - -#. Contributors to libvirt projects **must** assert that they are - in compliance with the `Developer Certificate of Origin - 1.1 <https://developercertificate.org/>`__. This is achieved by - adding a "Signed-off-by" line containing the contributor's name - and e-mail to every commit message. The presence of this line - attests that the contributor has read the above lined DCO and - agrees with its statements. - -#. Make sure your patches apply against libvirt GIT. Developers - only follow GIT and don't care much about released versions. - -#. Run the automated tests on your code before submitting any - changes. That is: - - :: - - make check - make syntax-check - -#. Update tests and/or documentation, particularly if you are - adding a new feature or changing the output of a program. - -#. Don't forget to update the `release notes <news.html>`__ by - changing ``docs/news.xml`` if your changes are significant. All - user-visible changes, such as adding new XML elements or fixing - all but the most obscure bugs, must be (briefly) described in a - release notes entry; changes that are only relevant to other - libvirt developers, such as code refactoring, don't belong in - the release notes. Note that ``docs/news.xml`` should be - updated in its own commit not to get in the way of backports. +============ +Contributing +============ + +These are the basics steps you need to follow to contribute to +libvirt. + +Repositories and external resources +=================================== + +The official upstream repository is kept in git +(``https://libvirt.org/git/libvirt.git``) and is browsable +along with other libvirt-related repositories (e.g. +libvirt-python) `online <https://libvirt.org/git/>`__. + +Patches to translations are maintained via the `zanata +project <https://fedora.zanata.org/>`__. If you want to fix a +translation in a .po file, join the appropriate language team. +The libvirt release process automatically pulls the latest +version of each translation file from zanata. + +Preparing patches +================= + +Make sure your patches apply against libvirt git. Developers +only follow git and don't care much about released versions. + +Run the automated tests on your code before submitting any +changes. That is: + +:: + + $ make check + $ make syntax-check + +These tests help making sure that your changes don't introduce +regressions in libvirt, as well as validating that any new code +follows the project's `coding style <coding-style.html>`__. + +If you're going to submit multiple patches, the automated tests +must pass **after each patch**, not just after the last one. + +Update tests and/or documentation, particularly if you are +adding a new feature or changing the output of a program, and +don't forget to update the `release notes <news.html>`__ if your +changes are significant and user-visible. + +Submitting patches +================== + +Libvirt uses a mailing list based development workflow. + +While preparing your patches for submissions, make sure you +follow the `best practices <best-practices.html>`__ and, once +you're satisfied with the result, go ahead and +`submit your patches <submitting-patches.html>`__. + +Developer Certificate of Origin +=============================== + +Contributors to libvirt projects **must** assert that they are +in compliance with the `Developer Certificate of Origin +1.1 <https://developercertificate.org/>`__. This is achieved by +adding a "Signed-off-by" line containing the contributor's name +and e-mail to every commit message. The presence of this line +attests that the contributor has read the above lined DCO and +agrees with its statements. + +Further reading +=============== + +This page only covers the very basics, so it's recommended that +you also take a look at the following documents: + +- `Programming languages <programming-languages.html>`__ +- `Developer tooling <developer-tooling.html>`__ +- `Advanced test suite usage <advanced-tests.html>`__ +- `Adoption of GLib APIs <glib-adoption.html>`__ +- `Committer guidelines <committer-guidelines.html>`__ -- 2.25.1
On Mon, Apr 06, 2020 at 06:20:00PM +0200, Andrea Bolognani wrote:
hacking.html is the canonical entry point for people looking to help with libvirt's development, but its sheer size makes it a farily ineffective tool.
Move most non-critical information off to separate pages and brush up what's left so that it works as a quick introduction.
As a prerequisite, convert the existing page to reStructuredText.
I have compared the HTML version and the conversion visually and didn't spot any massive differences, save for a few spacing changes that are not specific to the page itself but rather to the HTML generated by docutils and which will require CSS tweaks to address, which is a job I'm leaving to someone else.
I have also spent very little time actually changing the contents, and mostly just moved them around. There's plenty of opportunities for improvement there, but once again that's someone else's job.
Andrea Bolognani (10): docs: Convert hacking.html to reStructuredText docs: Add glib-adoption.rst docs: Add coding-style.rst docs: Add programming-languages.rst docs: Add developer-tooling.rst docs: Add committer-guidelines.rst docs: Add advanced-tests.rst docs: Add submitting-patches.rst docs: Add best-practices.rst docs: Update hacking.rst
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> but note a comment on patch 1 Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
participants (2)
-
Andrea Bolognani -
Daniel P. Berrangé