dnl dnl Enable all known GCC compiler warnings, except for those dnl we can't yet cope with dnl AC_DEFUN([LIBVIRT_GLIB_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" # gcc 4.2 treats attribute(format) as an implicit attribute(nonnull), # which triggers spurious warnings for our usage AC_CACHE_CHECK([whether the C compiler's -Wformat allows NULL strings], [lv_cv_gcc_wformat_null_works], [ save_CFLAGS=$CFLAGS CFLAGS='-Wunknown-pragmas -Werror -Wformat' AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ #include static __attribute__ ((__format__ (__printf__, 1, 2))) int foo (const char *fmt, ...) { return !fmt; } ]], [[ return foo(NULL); ]])], [lv_cv_gcc_wformat_null_works=yes], [lv_cv_gcc_wformat_null_works=no]) CFLAGS=$save_CFLAGS]) # 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="$dontwarn -Wmissing-declarations" dontwarn="$dontwarn -Wcast-align" else AC_DEFINE_UNQUOTED([WORKING_PRAGMA_PUSH], 1, [Define to 1 if gcc supports pragma push/pop]) fi dnl Check whether strchr(s, char variable) causes a bogus compile dnl warning, which is the case with GCC < 4.6 on some glibc AC_CACHE_CHECK([whether the C compiler's -Wlogical-op gives bogus warnings], [lv_cv_gcc_wlogical_op_broken], [ save_CFLAGS="$CFLAGS" CFLAGS="-O2 -Wlogical-op -Werror" AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ #include ]], [[ const char *haystack; char needle; return strchr(haystack, needle) == haystack;]])], [lv_cv_gcc_wlogical_op_broken=no], [lv_cv_gcc_wlogical_op_broken=yes]) CFLAGS="$save_CFLAGS"]) # 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="$dontwarn -Wpacked" dontwarn="$dontwarn -Wunused-macros" dontwarn="$dontwarn -Woverlength-strings" dontwarn="$dontwarn -Wstack-protector" # g_clear_object & G_ATOMIC_OP_USE_GCC_BUILTINS causes # violations with this. XXX Fix glib ? dontwarn="$dontwarn -Wbad-function-cast" # Due to gutils.h bug in g_bit_storage wantwarn="$wantwarn -Wno-sign-conversion" wantwarn="$wantwarn -Wno-conversion" # We can't enable this due to horrible spice_usb_device_get_description # signature wantwarn="$wantwarn -Wno-format-nonliteral" # 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]) # 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... wantwarn="$wantwarn -Wno-sign-compare" # GNULIB expects this to be part of -Wc++-compat, but we turn # that one off, so we need to manually enable this again wantwarn="$wantwarn -Wjump-misses-init" # We do "bad" function casts all the time for event callbacks wantwarn="$wantwarn -Wno-cast-function-type" # GNULIB turns on -Wformat=2 which implies -Wformat-nonliteral, # so we need to manually re-exclude it. Also, older gcc 4.2 # added an implied ATTRIBUTE_NONNULL on any parameter marked # ATTRIBUTE_FMT_PRINT, which causes -Wformat failure on our # intentional use of virReportError(code, NULL). wantwarn="$wantwarn -Wno-format-nonliteral" if test $lv_cv_gcc_wformat_null_works = no; then wantwarn="$wantwarn -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 wantwarn="$wantwarn -Wframe-larger-than=4096" dnl wantwarn="$wantwarn -Wframe-larger-than=256" # Extra special flags dnl -fstack-protector stuff passes gl_WARN_ADD with gcc dnl on Mingw32, but fails when actually used case $host in aarch64-*-*) dnl "error: -fstack-protector not supported for this target [-Werror]" ;; *-*-linux*) dnl Prefer -fstack-protector-strong if it's available. dnl There doesn't seem to be great overhead in adding dnl -fstack-protector-all instead of -fstack-protector. dnl dnl We also don't need ssp-buffer-size with -all or -strong, dnl since functions are protected regardless of buffer size. dnl wantwarn="$wantwarn --param=ssp-buffer-size=4" wantwarn="$wantwarn -fstack-protector-strong" ;; *-*-freebsd*) dnl FreeBSD ships old gcc 4.2.1 which doesn't handle dnl -fstack-protector-all well wantwarn="$wantwarn -fstack-protector" wantwarn="$wantwarn -Wno-unused-command-line-argument" ;; esac wantwarn="$wantwarn -fexceptions" wantwarn="$wantwarn -fasynchronous-unwind-tables" # Need -fipa-pure-const in order to make -Wsuggest-attribute=pure # fire even without -O. wantwarn="$wantwarn -fipa-pure-const" # We should eventually enable this, but right now there are at # least 75 functions triggering warnings. wantwarn="$wantwarn -Wno-suggest-attribute=pure" wantwarn="$wantwarn -Wno-suggest-attribute=const" if test "$set_werror" = "yes" then wantwarn="$wantwarn -Werror" fi # Check for $CC support of each warning for w in $wantwarn; do gl_WARN_ADD([$w]) done case $host in *-*-linux*) dnl Fall back to -fstack-protector-all if -strong is not available case $WARN_CFLAGS in *-fstack-protector-strong*) ;; *) gl_WARN_ADD(["-fstack-protector-all"]) ;; esac ;; esac # Silence certain warnings in gnulib, and use improved glibc headers AC_DEFINE([lint], [1], [Define to 1 if the compiler is checking for lint.]) AH_VERBATIM([FORTIFY_SOURCE], [/* Enable compile-time and run-time bounds-checking, and some warnings, without upsetting newer glibc. */ #if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__ # define _FORTIFY_SOURCE 2 #endif ]) if test "$gl_cv_warn_c__Wlogical_op" = yes && test "$lv_cv_gcc_wlogical_op_broken" = yes; then AC_DEFINE_UNQUOTED([BROKEN_GCC_WLOGICALOP], 1, [Define to 1 if gcc -Wlogical-op reports false positives on strchr]) fi ])