[PATCH] docs: point out that locals should be defined at the top of a block of code
Although we have nothing in make syntax-check to enforce this, and apparently there are places where it isn't the case (according to Dan), we should discourage the practice of defining new variables in the middle of a block of code. https://www.redhat.com/archives/libvir-list/2020-July/msg00433.html Signed-off-by: Laine Stump <laine@redhat.com> --- docs/coding-style.rst | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/docs/coding-style.rst b/docs/coding-style.rst index 03b89c86e5..b9b4a16987 100644 --- a/docs/coding-style.rst +++ b/docs/coding-style.rst @@ -541,6 +541,44 @@ 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. +Defining Local Variables +------------------------ + +Always define local variables at the top of the block in which they +are used (before any pure code). Although modern C compilers allow +defining a local variable in the middle of a block of code, this +practice can lead to bugs, and must be avoided in all libvirt +code. (As indicated in these examples, it is okay to initialize +variables where they are defined, even if the initialization involves +calling another function.) + +:: + + GOOD: + int + Bob(char *loblaw) + { + int x; + int y = lawBlog(loblaw); + char *z = NULL; + + x = y + 20; + ... + } + + BAD: + int + Bob(char *loblaw) + { + int x; + int y = lawBlog(loblaw); + + x = y + 20; + + char *z = NULL; <=== + ... + } + Attribute annotations --------------------- -- 2.25.4
On Thu, Jul 09, 2020 at 06:41:21PM -0400, Laine Stump wrote:
Although we have nothing in make syntax-check to enforce this, and apparently there are places where it isn't the case (according to Dan), we should discourage the practice of defining new variables in the middle of a block of code.
https://www.redhat.com/archives/libvir-list/2020-July/msg00433.html Signed-off-by: Laine Stump <laine@redhat.com> --- docs/coding-style.rst | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
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 :|
On Thu, 2020-07-09 at 18:41 -0400, Laine Stump wrote:
+Defining Local Variables +------------------------ + +Always define local variables at the top of the block in which they +are used (before any pure code). Although modern C compilers allow +defining a local variable in the middle of a block of code, this +practice can lead to bugs, and must be avoided in all libvirt +code. (As indicated in these examples, it is okay to initialize +variables where they are defined, even if the initialization involves +calling another function.)
The parentheses around the last sentence are unnecessary, please drop them.
+ GOOD: + int + Bob(char *loblaw) + { + int x; + int y = lawBlog(loblaw);
I believe this should be int y = lawBlog(); but note that I haven't compile-tested this alternative version.
+ BAD: + int + Bob(char *loblaw) + { + int x; + int y = lawBlog(loblaw); + + x = y + 20; + + char *z = NULL; <===
Please add // in front of the ASCII arrow. It's pretty weird how we use C++-style comments throughout our style guide, at the same time as *the style guide itself* instructs developers to use C-style comments instead, but addressing that is a job for another patch :) With the nits fixed, Reviewed-by: Andrea Bolognani <abologna@redhat.com> -- Andrea Bolognani / Red Hat / Virtualization
On Thu, Jul 09, 2020 at 06:41:21PM -0400, Laine Stump wrote:
Although we have nothing in make syntax-check to enforce this, and apparently there are places where it isn't the case (according to Dan), we should discourage the practice of defining new variables in the middle of a block of code.
https://www.redhat.com/archives/libvir-list/2020-July/msg00433.html Signed-off-by: Laine Stump <laine@redhat.com> --- docs/coding-style.rst | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
diff --git a/docs/coding-style.rst b/docs/coding-style.rst index 03b89c86e5..b9b4a16987 100644 --- a/docs/coding-style.rst +++ b/docs/coding-style.rst @@ -541,6 +541,44 @@ 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.
+Defining Local Variables +------------------------ + +Always define local variables at the top of the block in which they +are used (before any pure code). Although modern C compilers allow +defining a local variable in the middle of a block of code, this +practice can lead to bugs, and must be avoided in all libvirt +code. (As indicated in these examples, it is okay to initialize +variables where they are defined, even if the initialization involves +calling another function.) + +:: + + GOOD: + int + Bob(char *loblaw)
Since we are nitpicking I don't think we allow the first letter of the function name to be uppercase. :) Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
participants (4)
-
Andrea Bolognani -
Daniel P. Berrangé -
Laine Stump -
Pavel Hrdina