libvirt/m4/virt-compile-warnings.m4
Eric Blake 892242519a build: fix build on older gcc
On RHEL 6.2, gcc 4.4.6 complains:
cc1: warning: command line option "-Wenum-compare" is valid for C++/ObjC++ but not for C
which in turn breaks a -Werror build.

Meanwhile, in Fedora 17, gcc 4.7.0, -Wenum-compare has been enhanced
to also work on C, but at the same time, it is documented that -Wall
now implicitly includes -Wenum-compare.

Therefore, it is sufficient to remove explicit checks for this option,
avoiding the warning from older gcc while still getting the
compile-time safety from newer gcc.

* m4/virt-compile-warnings.m4 (-Wenum-compare): Omit explicit check.
2012-09-07 14:15:22 -06:00

183 lines
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dnl
dnl Enable all known GCC compiler warnings, except for those
dnl we can't yet cope with
dnl
AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
dnl ******************************
dnl More compiler warnings
dnl ******************************
AC_ARG_ENABLE([werror],
AS_HELP_STRING([--enable-werror], [Use -Werror (if supported)]),
[set_werror="$enableval"],
[if test -d $srcdir/.git; then
is_git_version=true
set_werror=yes
else
set_werror=no
fi])
# List of warnings that are not relevant / wanted
# Don't care about C++ compiler compat
dontwarn="$dontwarn -Wc++-compat"
dontwarn="$dontwarn -Wabi"
dontwarn="$dontwarn -Wdeprecated"
# Don't care about ancient C standard compat
dontwarn="$dontwarn -Wtraditional"
# Don't care about ancient C standard compat
dontwarn="$dontwarn -Wtraditional-conversion"
# Ignore warnings in /usr/include
dontwarn="$dontwarn -Wsystem-headers"
# Happy for compiler to add struct padding
dontwarn="$dontwarn -Wpadded"
# GCC very confused with -O2
dontwarn="$dontwarn -Wunreachable-code"
# Too many to deal with
dontwarn="$dontwarn -Wconversion"
# Too many to deal with
dontwarn="$dontwarn -Wsign-conversion"
# GNULIB gettext.h violates
dontwarn="$dontwarn -Wvla"
# Many GNULIB header violations
dontwarn="$dontwarn -Wundef"
# Need to allow bad cast for execve()
dontwarn="$dontwarn -Wcast-qual"
# We need to use long long in many places
dontwarn="$dontwarn -Wlong-long"
# We allow manual list of all enum cases without default:
dontwarn="$dontwarn -Wswitch-default"
# We allow optional default: instead of listing all enum values
dontwarn="$dontwarn -Wswitch-enum"
# Not a problem since we don't use -fstrict-overflow
dontwarn="$dontwarn -Wstrict-overflow"
# Not a problem since we don't use -funsafe-loop-optimizations
dontwarn="$dontwarn -Wunsafe-loop-optimizations"
# Things like virAsprintf mean we can't use this
dontwarn="$dontwarn -Wformat-nonliteral"
# Gnulib's stat-time.h violates this
dontwarn="$dontwarn -Waggregate-return"
# gcc 4.4.6 complains this is C++ only; gcc 4.7.0 implies this from -Wall
dontwarn="$dontwarn -Wenum-compare"
# Gnulib uses '#pragma GCC diagnostic push' to silence some
# warnings, but older gcc doesn't support this.
AC_CACHE_CHECK([whether pragma GCC diagnostic push works],
[lv_cv_gcc_pragma_push_works], [
save_CFLAGS=$CFLAGS
CFLAGS='-Wunknown-pragmas -Werror'
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#pragma GCC diagnostic push
#pragma GCC diagnostic pop
]])],
[lv_cv_gcc_pragma_push_works=yes],
[lv_cv_gcc_pragma_push_works=no])
CFLAGS=$save_CFLAGS])
if test $lv_cv_gcc_pragma_push_works = no; then
dontwarn="$dontwarn -Wmissing-prototypes"
dontwarn="$dontwarn -Wmissing-declarations"
fi
# We might fundamentally need some of these disabled forever, but
# ideally we'd turn many of them on
dontwarn="$dontwarn -Wfloat-equal"
dontwarn="$dontwarn -Wdeclaration-after-statement"
dontwarn="$dontwarn -Wcast-qual"
dontwarn="$dontwarn -Wconversion"
dontwarn="$dontwarn -Wsign-conversion"
dontwarn="$dontwarn -Wpacked"
dontwarn="$dontwarn -Wunused-macros"
dontwarn="$dontwarn -Woverlength-strings"
dontwarn="$dontwarn -Wstack-protector"
# Get all possible GCC warnings
gl_MANYWARN_ALL_GCC([maybewarn])
# Remove the ones we don't want, blacklisted earlier
gl_MANYWARN_COMPLEMENT([wantwarn], [$maybewarn], [$dontwarn])
# Check for $CC support of each warning
for w in $wantwarn; do
gl_WARN_ADD([$w])
done
# GNULIB uses '-W' (aka -Wextra) which includes a bunch of stuff.
# Unfortunately, this means you can't simply use '-Wsign-compare'
# with gl_MANYWARN_COMPLEMENT
# So we have -W enabled, and then have to explicitly turn off...
gl_WARN_ADD([-Wno-sign-compare])
# GNULIB expects this to be part of -Wc++-compat, but we turn
# that one off, so we need to manually enable this again
gl_WARN_ADD([-Wjump-misses-init])
# GNULIB turns on -Wformat=2 which implies -Wformat-nonliteral,
# so we need to manually re-exclude it. Also, older gcc 4.2
# added an implied ATTRIBUTE_NONNULL on any parameter marked
# ATTRIBUTE_FMT_PRINT, which causes -Wformat failure on our
# intentional use of virReportError(code, NULL).
gl_WARN_ADD([-Wno-format-nonliteral])
if test $lv_cv_gcc_pragma_push_works = no; then
gl_WARN_ADD([-Wno-format])
fi
# 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
gl_WARN_ADD([-Wframe-larger-than=4096])
dnl gl_WARN_ADD([-Wframe-larger-than=256])
# Silence certain warnings in gnulib, and use improved glibc headers
AC_DEFINE([lint], [1],
[Define to 1 if the compiler is checking for lint.])
AH_VERBATIM([FORTIFY_SOURCE],
[/* Enable compile-time and run-time bounds-checking, and some warnings,
without upsetting newer glibc. */
#if defined __OPTIMIZE__ && __OPTIMIZE__
# define _FORTIFY_SOURCE 2
#endif
])
# Extra special flags
dnl -fstack-protector stuff passes gl_WARN_ADD with gcc
dnl on Mingw32, but fails when actually used
case $host in
*-*-linux*)
dnl Fedora only uses -fstack-protector, but doesn't seem to
dnl be great overhead in adding -fstack-protector-all instead
dnl gl_WARN_ADD([-fstack-protector])
gl_WARN_ADD([-fstack-protector-all])
gl_WARN_ADD([--param=ssp-buffer-size=4])
;;
esac
gl_WARN_ADD([-fexceptions])
gl_WARN_ADD([-fasynchronous-unwind-tables])
gl_WARN_ADD([-fdiagnostics-show-option])
gl_WARN_ADD([-funit-at-a-time])
# Need -fipa-pure-const in order to make -Wsuggest-attribute=pure
# fire even without -O.
gl_WARN_ADD([-fipa-pure-const])
# We should eventually enable this, but right now there are at
# least 75 functions triggering warnings.
gl_WARN_ADD([-Wno-suggest-attribute=pure])
gl_WARN_ADD([-Wno-suggest-attribute=const])
if test "$set_werror" = "yes"
then
gl_WARN_ADD([-Werror])
fi
WARN_LDFLAGS=$WARN_CFLAGS
AC_SUBST([WARN_CFLAGS])
AC_SUBST([WARN_LDFLAGS])
dnl Needed to keep compile quiet on python 2.4
save_WARN_CFLAGS=$WARN_CFLAGS
WARN_CFLAGS=
gl_WARN_ADD([-Wno-redundant-decls])
WARN_PYTHON_CFLAGS=$WARN_CFLAGS
AC_SUBST(WARN_PYTHON_CFLAGS)
WARN_CFLAGS=$save_WARN_CFLAGS
])