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42af2167a4
A previous patch (c606671a) pulled in a newer version of
stat-time.h from gnulib, which causes some warnings in older gcc:
CC libvirt_driver_storage_la-storage_backend.lo
cc1: warnings being treated as errors
In file included from ../../src/storage/storage_backend.c:59:
../../gnulib/lib/stat-time.h:55: error: no previous prototype for 'get_stat_atime_ns' [-Wmissing-prototypes]
Upstream gnulib argues that these warnings are stupid (and I agree;
see <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54113>), and has
used a modern gcc feature (#pragma GCC diagnostic push) to avoid the
warning. But we still aim to compile on RHEL 6.3, with gcc 4.4.6
(not to mention even older platforms like RHEL 5), and therefore
the warning trips up our default of development with -Werror.
It took me a while to figure out how to make our set of warnings
smaller on older gcc without losing the benefit of the warnings
when using newer gcc (such as the one on Fedora 17), but this
should do the trick.
* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Avoid
warnings that gnulib can't silence on older gcc.
175 lines
6.3 KiB
Plaintext
175 lines
6.3 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([werror],
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AS_HELP_STRING([--enable-werror], [Use -Werror (if supported)]),
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[set_werror="$enableval"],
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[if test -d $srcdir/.git; then
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is_git_version=true
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set_werror=yes
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else
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set_werror=no
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fi])
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# List of warnings that are not relevant / wanted
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# Don't care about C++ compiler compat
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dontwarn="$dontwarn -Wc++-compat"
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dontwarn="$dontwarn -Wabi"
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dontwarn="$dontwarn -Wdeprecated"
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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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# Gnulib's stat-time.h violates this
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dontwarn="$dontwarn -Waggregate-return"
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# Gnulib uses '#pragma GCC diagnostic push' to silence some
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# warnings, but older gcc doesn't support this.
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AC_CACHE_CHECK([whether pragma GCC diagnostic push works],
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[lv_cv_gcc_pragma_push_works], [
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save_CFLAGS=$CFLAGS
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CFLAGS='-Wunknown-pragmas -Werror'
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
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#pragma GCC diagnostic push
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#pragma GCC diagnostic pop
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]])],
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[lv_cv_gcc_pragma_push_works=yes],
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[lv_cv_gcc_pragma_push_works=no])
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CFLAGS=$save_CFLAGS])
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if test $lv_cv_gcc_pragma_push_works = no; then
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dontwarn="$dontwarn -Wmissing-prototypes"
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dontwarn="$dontwarn -Wmissing-declarations"
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fi
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# We might fundamentally need some of these disabled forever, but
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# ideally we'd turn many of them on
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dontwarn="$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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# Silence certain warnings in gnulib, and use improved glibc headers
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AC_DEFINE([lint], [1],
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[Define to 1 if the compiler is checking for lint.])
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AH_VERBATIM([FORTIFY_SOURCE],
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[/* Enable compile-time and run-time bounds-checking, and some warnings,
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without upsetting newer glibc. */
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#if defined __OPTIMIZE__ && __OPTIMIZE__
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# define _FORTIFY_SOURCE 2
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#endif
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])
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# Extra special flags
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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 $host in
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*-*-linux*)
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dnl Fedora only uses -fstack-protector, but doesn't seem to
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dnl be great overhead in adding -fstack-protector-all instead
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dnl gl_WARN_ADD([-fstack-protector])
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gl_WARN_ADD([-fstack-protector-all])
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gl_WARN_ADD([--param=ssp-buffer-size=4])
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;;
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esac
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gl_WARN_ADD([-fexceptions])
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gl_WARN_ADD([-fasynchronous-unwind-tables])
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gl_WARN_ADD([-fdiagnostics-show-option])
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gl_WARN_ADD([-funit-at-a-time])
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# Need -fipa-pure-const in order to make -Wsuggest-attribute=pure
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# fire even without -O.
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gl_WARN_ADD([-fipa-pure-const])
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# We should eventually enable this, but right now there are at
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# least 75 functions triggering warnings.
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gl_WARN_ADD([-Wno-suggest-attribute=pure])
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gl_WARN_ADD([-Wno-suggest-attribute=const])
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if test "$set_werror" = "yes"
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then
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gl_WARN_ADD([-Werror])
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fi
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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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