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75da320087
I had previously tested commit 059d746
with -O intentionally omitted
from my CFLAGS; but that means that I missed out on this warning
from gcc 4.6.2 when optimizations are enabled:
util/buf.c: In function 'virBufferGetIndent':
util/buf.c:86:1: error: function might be candidate for attribute 'pure' [-Werror=suggest-attribute=pure]
While it is probably a good idea to add the attributes and silence
this warning, it's also invasive; 'make -k' found more than 75 such
complaints. And it doesn't help that gcc 4.6.2 is still buggy
(coreutils reported a case where gcc 4.6.2 incorrectly suggested
marking a function pure that incremented a global variable; fixed
in gcc 4.7). So the best fix for now is to disable the warning.
It also doesn't help that I stumbled across another problem - gcc
documents that -Wsuggest-attribute=pure only warns if you use -O,
or if you use -fipa-pure-const. But in practice, when I omitted -O
but added -fipa-pure-const, the warnings are fickle - I got warnings
for simple compilation that disappeared when I also added -fPIC.
And the way libtool compiles things is with -fPIC first, then without
-fPIC but with errors sent to /dev/null - which meant that without
disabling -Wsuggest-attribute=pure, I got a compile error with no
message. :( See http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10197
* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Silence
-Wsuggest-attribute warnings for now.
149 lines
5.6 KiB
Plaintext
149 lines
5.6 KiB
Plaintext
dnl
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dnl Enable all known GCC compiler warnings, except for those
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dnl we can't yet cope with
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dnl
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AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
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dnl ******************************
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dnl More compiler warnings
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dnl ******************************
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AC_ARG_ENABLE(compile-warnings,
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[AC_HELP_STRING([--enable-compile-warnings=@<:@no/yes/error@:>@],
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[Turn on compiler warnings])],,
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[enable_compile_warnings="m4_default([$1],[yes])"])
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case "$enable_compile_warnings" in
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no)
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try_compiler_flags=""
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;;
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yes|minimum|maximum|error)
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# List of warnings that are not relevant / wanted
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# Don't care about C++ compiler compat
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dontwarn="$dontwarn -Wc++-compat"
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# Don't care about ancient C standard compat
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dontwarn="$dontwarn -Wtraditional"
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# Don't care about ancient C standard compat
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dontwarn="$dontwarn -Wtraditional-conversion"
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# Ignore warnings in /usr/include
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dontwarn="$dontwarn -Wsystem-headers"
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# Happy for compiler to add struct padding
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dontwarn="$dontwarn -Wpadded"
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# GCC very confused with -O2
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dontwarn="$dontwarn -Wunreachable-code"
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# Too many to deal with
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dontwarn="$dontwarn -Wconversion"
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# Too many to deal with
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dontwarn="$dontwarn -Wsign-conversion"
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# GNULIB gettext.h violates
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dontwarn="$dontwarn -Wvla"
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# Many GNULIB header violations
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dontwarn="$dontwarn -Wundef"
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# Need to allow bad cast for execve()
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dontwarn="$dontwarn -Wcast-qual"
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# We need to use long long in many places
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dontwarn="$dontwarn -Wlong-long"
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# We allow manual list of all enum cases without default:
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dontwarn="$dontwarn -Wswitch-default"
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# We allow optional default: instead of listing all enum values
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dontwarn="$dontwarn -Wswitch-enum"
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# Not a problem since we don't use -fstrict-overflow
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dontwarn="$dontwarn -Wstrict-overflow"
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# Not a problem since we don't use -funsafe-loop-optimizations
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dontwarn="$dontwarn -Wunsafe-loop-optimizations"
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# Things like virAsprintf mean we can't use this
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dontwarn="$dontwarn -Wformat-nonliteral"
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# We might fundamentally need some of these disabled forever, but
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# ideally we'd turn many of them on
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dontwarn="$dontwarn -Wfloat-equal"
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dontwarn="$dontwarn -Wdeclaration-after-statement"
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dontwarn="$dontwarn -Wcast-qual"
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dontwarn="$dontwarn -Wconversion"
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dontwarn="$dontwarn -Wsign-conversion"
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dontwarn="$dontwarn -Wpacked"
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dontwarn="$dontwarn -Wunused-macros"
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dontwarn="$dontwarn -Woverlength-strings"
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dontwarn="$dontwarn -Wstack-protector"
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# Get all possible GCC warnings
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gl_MANYWARN_ALL_GCC([maybewarn])
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# Remove the ones we don't want, blacklisted earlier
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gl_MANYWARN_COMPLEMENT([wantwarn], [$maybewarn], [$dontwarn])
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# Check for $CC support of each warning
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for w in $wantwarn; do
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gl_WARN_ADD([$w])
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done
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# GNULIB uses '-W' (aka -Wextra) which includes a bunch of stuff.
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# Unfortunately, this means you can't simply use '-Wsign-compare'
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# with gl_MANYWARN_COMPLEMENT
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# So we have -W enabled, and then have to explicitly turn off...
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gl_WARN_ADD([-Wno-sign-compare])
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# GNULIB expects this to be part of -Wc++-compat, but we turn
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# that one off, so we need to manually enable this again
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gl_WARN_ADD([-Wjump-misses-init])
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# GNULIB turns on -Wformat=2 which implies -Wformat-nonliteral,
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# so we need to manually re-exclude it.
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gl_WARN_ADD([-Wno-format-nonliteral])
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# This should be < 256 really. Currently we're down to 4096,
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# but using 1024 bytes sized buffers (mostly for virStrerror)
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# stops us from going down further
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gl_WARN_ADD([-Wframe-larger-than=4096])
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dnl gl_WARN_ADD([-Wframe-larger-than=256])
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# Extra special flags
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gl_WARN_ADD([-Wp,-D_FORTIFY_SOURCE=2])
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dnl -fstack-protector stuff passes gl_WARN_ADD with gcc
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dnl on Mingw32, but fails when actually used
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case $host in
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*-*-linux*)
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dnl Fedora only uses -fstack-protector, but doesn't seem to
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dnl be great overhead in adding -fstack-protector-all instead
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dnl gl_WARN_ADD([-fstack-protector])
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gl_WARN_ADD([-fstack-protector-all])
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gl_WARN_ADD([--param=ssp-buffer-size=4])
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;;
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esac
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gl_WARN_ADD([-fexceptions])
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gl_WARN_ADD([-fasynchronous-unwind-tables])
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gl_WARN_ADD([-fdiagnostics-show-option])
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gl_WARN_ADD([-funit-at-a-time])
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# Need -fipa-pure-const in order to make -Wsuggest-attribute=pure
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# fire even without -O.
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gl_WARN_ADD([-fipa-pure-const])
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# We should eventually enable this, but right now there are at
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# least 75 functions triggering warnings.
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gl_WARN_ADD([-Wno-suggest-attribute=pure])
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gl_WARN_ADD([-Wno-suggest-attribute=const])
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if test "$enable_compile_warnings" = "error"
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then
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gl_WARN_ADD([-Werror])
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fi
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;;
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*)
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AC_MSG_ERROR(Unknown argument '$enable_compile_warnings' to --enable-compile-warnings)
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;;
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esac
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WARN_LDFLAGS=$WARN_CFLAGS
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AC_SUBST([WARN_CFLAGS])
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AC_SUBST([WARN_LDFLAGS])
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dnl Needed to keep compile quiet on python 2.4
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save_WARN_CFLAGS=$WARN_CFLAGS
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WARN_CFLAGS=
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gl_WARN_ADD([-Wno-redundant-decls])
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WARN_PYTHON_CFLAGS=$WARN_CFLAGS
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AC_SUBST(WARN_PYTHON_CFLAGS)
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WARN_CFLAGS=$save_WARN_CFLAGS
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])
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