We're not using these warning flags with libvirt, and it is not worth keeping them just to issue a warning if someone tries to enable them. If someone does try to enable them, either libvirt will build cleanly or it won't. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- meson.build | 76 ----------------------------------------------------- 1 file changed, 76 deletions(-) diff --git a/meson.build b/meson.build index b827bd9275..7565eace17 100644 --- a/meson.build +++ b/meson.build @@ -491,82 +491,6 @@ if not cc.compiles(w_unused_function_code, args: w_unused_function_args) cc_flags += ['-Wno-unused-function'] endif -cc_flags_disabled = [ - # In meson this is specified using 'c_std=gnu99' in project() function. - '-std=gnu99', - - # don't care about C++ compiler compat - '-Wc++-compat', - '-Wabi', - '-Wdeprecated', - - # Don't care about ancient C standard compat - '-Wtraditional', - '-Wtraditional-conversion', - - # Ignore warnings in /usr/include - '-Wsystem-headers', - - # Happy for compiler to add struct padding - '-Wpadded', - - # GCC very confused with -O2 - '-Wunreachable-code', - - # Too many to deal with - '-Wconversion', - '-Wsign-conversion', - - # Need to allow bad cast for execve() - '-Wcast-qual', - - # We need to use long long in many places - '-Wlong-long', - - # We allow manual list of all enum cases without default - '-Wswitch-default', - - # Not a problem since we don't use -fstrict-overflow - '-Wstrict-overflow', - - # Not a problem since we don't use -funsafe-loop-optimizations - '-Wunsafe-loop-optimizations', - - # gcc 4.4.6 complains this is C++ only; gcc 4.7.0 implies this from -Wall - '-Wenum-compare', - - # gcc 5.1 -Wformat-signedness mishandles enums, not ready for prime time - '-Wformat-signedness', - - # Several conditionals expand the same on both branches depending on the - # particular platform/architecture - '-Wduplicated-branches', - - # > This warning does not generally indicate that there is anything wrong - # > with your code; it merely indicates that GCC's optimizers are unable - # > to handle the code effectively. - # Source: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html - '-Wdisabled-optimization', - - # Various valid glib APIs/macros trigger this warning - '-Wbad-function-cast', - - # We might fundamentally need some of these disabled forever, but - # ideally we'd turn many of them on - '-Wfloat-equal', - '-Wpacked', - '-Wunused-macros', - '-Woverlength-strings', - '-Wstack-protector', - '-Wsuggest-attribute=malloc', -] - -foreach flag : cc_flags_disabled - if cc_flags.contains(flag) - error('@0@ is disabled but listed in cc_flags'.format(flag)) - endif -endforeach - supported_cc_flags = cc.get_supported_arguments(cc_flags) add_project_arguments(supported_cc_flags, language: 'c') -- 2.30.2

The split of arrays is fairly arbitrary and a hang over from the way we had to structure lists of flags when we used GNULIB's compiler flag checking m4 logic. The separate lists leads to cases where we enable a flag in one list and have contradictory setting in another list, which leads to confusion. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- meson.build | 116 +++++++++++++++++++--------------------------------- 1 file changed, 43 insertions(+), 73 deletions(-) diff --git a/meson.build b/meson.build index 97d9c52165..55dde6d963 100644 --- a/meson.build +++ b/meson.build @@ -211,7 +211,23 @@ if git_werror.enabled() or git_werror.auto() and git cc_flags += [ '-Werror' ] endif + +# gcc --help=warnings outputs +ptrdiff_max = cc.sizeof('ptrdiff_t', prefix: '#include <stddef.h>') +size_max = cc.sizeof('size_t', prefix: '#include <stdint.h>') +# Compute max safe object size by checking ptrdiff_t and size_t sizes. +# Ideally we would get PTRDIFF_MAX and SIZE_MAX values but it would +# give us (2147483647L) and we would have to remove the () and the suffix +# in order to convert it to numbers to be able to pick the smaller one. +alloc_max = run_command( + 'python3', '-c', + 'print(min(2**(@0@ * 8 - 1) - 1, 2**(@1@ * 8) - 1))'.format(ptrdiff_max, size_max), +) + cc_flags += [ + '-fasynchronous-unwind-tables', + '-fexceptions', + '-fipa-pure-const', '-fno-common', '-W', '-Wabsolute-value', @@ -219,6 +235,9 @@ cc_flags += [ '-Waddress-of-packed-member', '-Waggressive-loop-optimizations', '-Wall', + &#39;-Walloc-size-larger-than=@0(a)&#39;.format(alloc_max.stdout().strip()), + '-Warray-bounds=2', + '-Wattribute-alias=2', '-Wattribute-warning', '-Wattributes', '-Wbool-compare', @@ -228,7 +247,8 @@ cc_flags += [ '-Wcannot-profile', '-Wcast-align', '-Wcast-align=strict', - '-Wcast-function-type', + # We do "bad" function casts all the time for event callbacks + '-Wno-cast-function-type', '-Wchar-subscripts', '-Wclobbered', '-Wcomment', @@ -251,17 +271,24 @@ cc_flags += [ '-Wextra', '-Wformat-contains-nul', '-Wformat-extra-args', - '-Wformat-nonliteral', + # -Wformat=2 implies -Wformat-nonliteral so we need to manually exclude it + '-Wno-format-nonliteral', + '-Wformat-overflow=2', '-Wformat-security', + # -Wformat enables this by default, and we should keep it, + # but need to rewrite various areas of code first + '-Wno-format-truncation', '-Wformat-y2k', '-Wformat-zero-length', '-Wframe-address', + '-Wframe-larger-than=4096', '-Wfree-nonheap-object', '-Whsa', '-Wif-not-aligned', '-Wignored-attributes', '-Wignored-qualifiers', '-Wimplicit', + '-Wimplicit-fallthrough=5', '-Wimplicit-function-declaration', '-Wimplicit-int', '-Wincompatible-pointer-types', @@ -272,6 +299,7 @@ cc_flags += [ '-Wint-to-pointer-cast', '-Winvalid-memory-model', '-Winvalid-pch', + '-Wjump-misses-init', '-Wlogical-not-parentheses', '-Wlogical-op', '-Wmain', @@ -293,6 +321,7 @@ cc_flags += [ '-Wnested-externs', '-Wnonnull', '-Wnonnull-compare', + '-Wnormalized=nfc', '-Wnull-dereference', '-Wodr', '-Wold-style-declaration', @@ -318,32 +347,41 @@ cc_flags += [ '-Wshift-count-negative', '-Wshift-count-overflow', '-Wshift-negative-value', + '-Wshift-overflow=2', + # So we have -W enabled, and then have to explicitly turn off... + '-Wno-sign-compare', '-Wsizeof-array-argument', '-Wsizeof-pointer-div', '-Wsizeof-pointer-memaccess', '-Wstrict-aliasing', '-Wstrict-prototypes', + '-Wstringop-overflow=2', '-Wstringop-truncation', '-Wsuggest-attribute=cold', - '-Wsuggest-attribute=const', + '-Wno-suggest-attribute=const', '-Wsuggest-attribute=format', '-Wsuggest-attribute=noreturn', - '-Wsuggest-attribute=pure', + '-Wno-suggest-attribute=pure', '-Wsuggest-final-methods', '-Wsuggest-final-types', '-Wswitch', '-Wswitch-bool', + '-Wswitch-enum', '-Wswitch-unreachable', '-Wsync-nand', '-Wtautological-compare', '-Wtrampolines', '-Wtrigraphs', '-Wtype-limits', + # Clang incorrectly complains about dup typedefs win gnu99 mode + # so use this Clang-specific arg to keep it quiet + '-Wno-typedef-redefinition', '-Wuninitialized', '-Wunknown-pragmas', '-Wunused', '-Wunused-but-set-parameter', '-Wunused-but-set-variable', + '-Wunused-const-variable=2', '-Wunused-function', '-Wunused-label', '-Wunused-local-typedefs', @@ -355,79 +393,11 @@ cc_flags += [ '-Wvariadic-macros', '-Wvector-operation-performance', '-Wvla', + '-Wvla-larger-then=4031', '-Wvolatile-register-var', '-Wwrite-strings', ] -# gcc --help=warnings outputs -ptrdiff_max = cc.sizeof('ptrdiff_t', prefix: '#include <stddef.h>') -size_max = cc.sizeof('size_t', prefix: '#include <stdint.h>') -# Compute max safe object size by checking ptrdiff_t and size_t sizes. -# Ideally we would get PTRDIFF_MAX and SIZE_MAX values but it would -# give us (2147483647L) and we would have to remove the () and the suffix -# in order to convert it to numbers to be able to pick the smaller one. -alloc_max = run_command( - 'python3', '-c', - 'print(min(2**(@0@ * 8 - 1) - 1, 2**(@1@ * 8) - 1))'.format(ptrdiff_max, size_max), -) -cc_flags += [ - &#39;-Walloc-size-larger-than=@0(a)&#39;.format(alloc_max.stdout().strip()), - '-Warray-bounds=2', - '-Wattribute-alias=2', - '-Wformat-overflow=2', - '-Wformat-truncation=2', - '-Wimplicit-fallthrough=5', - '-Wnormalized=nfc', - '-Wshift-overflow=2', - '-Wstringop-overflow=2', - '-Wunused-const-variable=2', - '-Wvla-larger-then=4031', -] - -cc_flags += [ - # So we have -W enabled, and then have to explicitly turn off... - '-Wno-sign-compare', - - # We do "bad" function casts all the time for event callbacks - '-Wno-cast-function-type', - - # Clang incorrectly complains about dup typedefs win gnu99 mode - # so use this Clang-specific arg to keep it quiet - '-Wno-typedef-redefinition', - - # We don't use -Wc++-compat so we have to enable it explicitly - '-Wjump-misses-init', - - # -Wswitch is enabled but that doesn't report missing enums if a default: - # is present - '-Wswitch-enum', - - # -Wformat=2 implies -Wformat-nonliteral so we need to manually exclude it - '-Wno-format-nonliteral', - - # -Wformat enables this by default, and we should keep it, - # but need to rewrite various areas of code first - '-Wno-format-truncation', - - # This should be < 256 really. Currently we're down to 4096, - # but using 1024 bytes sized buffers (mostly for virStrerror) - # stops us from going down further - '-Wframe-larger-than=4096', - - # extra special flags - '-fexceptions', - '-fasynchronous-unwind-tables', - - # Need -fipa-pure-const in order to make -Wsuggest-attribute=pure - # fire even without -O. - '-fipa-pure-const', - - # We should eventually enable this, but right now there are at - # least 75 functions triggering warnings. - '-Wno-suggest-attribute=pure', - '-Wno-suggest-attribute=const', -] - # on aarch64 error: -fstack-protector not supported for this target if host_machine.cpu_family() != 'aarch64' if host_machine.system() in [ 'linux', 'freebsd', 'windows' ] -- 2.30.2

On Thu, Apr 08, 2021 at 01:30:18PM +0200, Pavel Hrdina wrote: It is outdated because virStrerror doesnt exist, and also at this point I don't think we need to really care about optimizing further than 4k - my original 256 byte statement is overkill. With 8 MB stacks, a 4k limit lets us recurse 2048 times in the worst case, and much much much in the common case. 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 :|

In several cases we check if a compiler flag is supported, and then add it to the 'cc_flags' array. The entire 'cc_flags' array is then later tested to see if each flag is supported, which duplicates the check in some cases. Move the check of cc_flags earlier, and for the extra flags append directly to supported_cc_flags to avoid the duplicate check Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- meson.build | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/meson.build b/meson.build index 55dde6d963..cf0e4f5715 100644 --- a/meson.build +++ b/meson.build @@ -398,6 +398,8 @@ cc_flags += [ '-Wwrite-strings', ] +supported_cc_flags = cc.get_supported_arguments(cc_flags) + # on aarch64 error: -fstack-protector not supported for this target if host_machine.cpu_family() != 'aarch64' if host_machine.system() in [ 'linux', 'freebsd', 'windows' ] @@ -406,7 +408,7 @@ if host_machine.cpu_family() != 'aarch64' '-fstack-protector-strong', '-fstack-protector-all', ]) - cc_flags += fstack_cflags + supported_cc_flags += fstack_cflags # When building with mingw using -fstack-protector requires libssp library # which is included by using -fstack-protector with linker. @@ -416,7 +418,7 @@ if host_machine.cpu_family() != 'aarch64' endif endif -if cc.has_argument('-Wlogical-op') +if supported_cc_flags.contains('-Wlogical-op') # Broken in 6.0 and later # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69602 w_logical_op_args = ['-O2', '-Wlogical-op', '-Werror'] @@ -445,7 +447,7 @@ w_double_promotion_code = ''' } ''' if cc.compiles(w_double_promotion_code, args: w_double_promotion_args, name: '-Wdouble-promotion') - cc_flags += ['-Wdouble-promotion'] + supported_cc_flags += ['-Wdouble-promotion'] endif # Clang complains about unused static inline functions which are common @@ -458,10 +460,9 @@ w_unused_function_code = ''' ''' # -Wunused-function is implied by -Wall, we must turn it off explicitly. if not cc.compiles(w_unused_function_code, args: w_unused_function_args) - cc_flags += ['-Wno-unused-function'] + supported_cc_flags += ['-Wno-unused-function'] endif -supported_cc_flags = cc.get_supported_arguments(cc_flags) add_project_arguments(supported_cc_flags, language: 'c') if cc.has_argument('-Wsuggest-attribute=format') -- 2.30.2

Meson has its own mechanism to turn on -Werror with the -Dwerror option. If this is set, then there is no reason for libvirt to check for -Werror itself. We remove the summary line output because it is potentially misleading when libvirt hasn't enabled -Werror, but meson has. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- meson.build | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/meson.build b/meson.build index 9fda0c7948..725d0e1cf0 100644 --- a/meson.build +++ b/meson.build @@ -207,7 +207,7 @@ cc = meson.get_compiler('c') cc_flags = [] git_werror = get_option('git_werror') -if git_werror.enabled() or git_werror.auto() and git +if (git_werror.enabled() or git_werror.auto()) and git and not get_option('werror') cc_flags += [ '-Werror' ] endif @@ -2300,7 +2300,6 @@ else loader_res = '' endif misc_summary = { - 'Use -Werror': cc_flags.contains('-Werror'), 'Warning Flags': supported_cc_flags, 'docs': gen_docs, 'tests': build_tests, -- 2.30.2