mirror of
https://gitlab.com/libvirt/libvirt.git
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d713a6b120
fdstream.c: In function 'virFDStreamWrite':
fdstream.c:390:29: error: logical 'or' of equal expressions [-Werror=logical-op]
if (errno == EAGAIN || errno == EWOULDBLOCK) {
^~
Fedora rawhide now uses gcc 6.0 and there is a bug with -Wlogical-op
producing false warnings.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69602
Use GCC pragma push/pop and ignore -Wlogical-op for GCC that supports
push/pop pragma and also has this bug.
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
263 lines
9.8 KiB
Plaintext
263 lines
9.8 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="$dontwarn -Waggregate-return"
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# gcc 4.4.6 complains this is C++ only; gcc 4.7.0 implies this from -Wall
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dontwarn="$dontwarn -Wenum-compare"
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# gcc 5.1 -Wformat-signedness mishandles enums, not ready for prime time
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dontwarn="$dontwarn -Wformat-signedness"
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# gcc 4.2 treats attribute(format) as an implicit attribute(nonnull),
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# which triggers spurious warnings for our usage
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AC_CACHE_CHECK([whether the C compiler's -Wformat allows NULL strings],
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[lv_cv_gcc_wformat_null_works], [
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save_CFLAGS=$CFLAGS
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CFLAGS='-Wunknown-pragmas -Werror -Wformat'
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
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#include <stddef.h>
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static __attribute__ ((__format__ (__printf__, 1, 2))) int
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foo (const char *fmt, ...) { return !fmt; }
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]], [[
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return foo(NULL);
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]])],
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[lv_cv_gcc_wformat_null_works=yes],
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[lv_cv_gcc_wformat_null_works=no])
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CFLAGS=$save_CFLAGS])
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# Gnulib uses '#pragma GCC diagnostic push' to silence some
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# warnings, but older gcc doesn't support this.
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AC_CACHE_CHECK([whether pragma GCC diagnostic push works],
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[lv_cv_gcc_pragma_push_works], [
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save_CFLAGS=$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="$dontwarn -Wmissing-declarations"
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dontwarn="$dontwarn -Wcast-align"
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else
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AC_DEFINE_UNQUOTED([WORKING_PRAGMA_PUSH], 1,
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[Define to 1 if gcc supports pragma push/pop])
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fi
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dnl Check whether strchr(s, char variable) causes a bogus compile
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dnl warning, which is the case with GCC < 4.6 on some glibc
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AC_CACHE_CHECK([whether the C compiler's -Wlogical-op gives bogus warnings],
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[lv_cv_gcc_wlogical_op_broken], [
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save_CFLAGS="$CFLAGS"
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CFLAGS="-O2 -Wlogical-op -Werror"
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
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#include <string.h>
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]], [[
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const char *haystack;
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char needle;
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return strchr(haystack, needle) == haystack;]])],
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[lv_cv_gcc_wlogical_op_broken=no],
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[lv_cv_gcc_wlogical_op_broken=yes])
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CFLAGS="$save_CFLAGS"])
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AC_CACHE_CHECK([whether gcc gives bogus warnings for -Wlogical-op],
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[lv_cv_gcc_wlogical_op_equal_expr_broken], [
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save_CFLAGS="$CFLAGS"
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CFLAGS="-O2 -Wlogical-op -Werror"
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
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#define TEST1 1
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#define TEST2 TEST1
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]], [[
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int test = 0;
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return test == TEST1 || test == TEST2;]])],
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[lv_cv_gcc_wlogical_op_equal_expr_broken=no],
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[lv_cv_gcc_wlogical_op_equal_expr_broken=yes])
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CFLAGS="$save_CFLAGS"])
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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="$dontwarn -Wpacked"
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dontwarn="$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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# 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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wantwarn="$wantwarn -Wno-sign-compare"
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# GNULIB expects this to be part of -Wc++-compat, but we turn
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# that one off, so we need to manually enable this again
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wantwarn="$wantwarn -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. Also, older gcc 4.2
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# added an implied ATTRIBUTE_NONNULL on any parameter marked
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# ATTRIBUTE_FMT_PRINT, which causes -Wformat failure on our
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# intentional use of virReportError(code, NULL).
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wantwarn="$wantwarn -Wno-format-nonliteral"
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if test $lv_cv_gcc_wformat_null_works = no; then
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wantwarn="$wantwarn -Wno-format"
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fi
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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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wantwarn="$wantwarn -Wframe-larger-than=4096"
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dnl wantwarn="$wantwarn -Wframe-larger-than=256"
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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 $host in
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aarch64-*-*)
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dnl "error: -fstack-protector not supported for this target [-Werror]"
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;;
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*-*-linux*)
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dnl Prefer -fstack-protector-strong if it's available.
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dnl There doesn't seem to be great overhead in adding
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dnl -fstack-protector-all instead of -fstack-protector.
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dnl
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dnl We also don't need ssp-buffer-size with -all or -strong,
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dnl since functions are protected regardless of buffer size.
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dnl wantwarn="$wantwarn --param=ssp-buffer-size=4"
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wantwarn="$wantwarn -fstack-protector-strong"
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;;
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*-*-freebsd*)
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dnl FreeBSD ships old gcc 4.2.1 which doesn't handle
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dnl -fstack-protector-all well
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wantwarn="$wantwarn -fstack-protector"
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wantwarn="$wantwarn -Wno-unused-command-line-argument"
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;;
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esac
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wantwarn="$wantwarn -fexceptions"
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wantwarn="$wantwarn -fasynchronous-unwind-tables"
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# Need -fipa-pure-const in order to make -Wsuggest-attribute=pure
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# fire even without -O.
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wantwarn="$wantwarn -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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wantwarn="$wantwarn -Wno-suggest-attribute=pure"
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wantwarn="$wantwarn -Wno-suggest-attribute=const"
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if test "$set_werror" = "yes"
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then
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wantwarn="$wantwarn -Werror"
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fi
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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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case $host in
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*-*-linux*)
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dnl Fall back to -fstack-protector-all if -strong is not available
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case $WARN_CFLAGS in
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*-fstack-protector-strong*)
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;;
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*)
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gl_WARN_ADD(["-fstack-protector-all"])
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;;
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esac
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;;
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esac
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case $WARN_CFLAGS in
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*-Wsuggest-attribute=format*)
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AC_DEFINE([HAVE_SUGGEST_ATTRIBUTE_FORMAT], [1], [Whether -Wsuggest-attribute=format works])
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;;
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esac
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# Silence certain warnings in gnulib, and use improved glibc headers
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AC_DEFINE([lint], [1],
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[Define to 1 if the compiler is checking for lint.])
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AH_VERBATIM([FORTIFY_SOURCE],
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[/* Enable compile-time and run-time bounds-checking, and some warnings,
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without upsetting newer glibc. */
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#if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
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# define _FORTIFY_SOURCE 2
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#endif
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])
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if test "$gl_cv_warn_c__Wlogical_op" = yes &&
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test "$lv_cv_gcc_wlogical_op_broken" = yes; then
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AC_DEFINE_UNQUOTED([BROKEN_GCC_WLOGICALOP_STRCHR], 1,
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[Define to 1 if gcc -Wlogical-op reports false positives on strchr])
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fi
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if test "$gl_cv_warn_c__Wlogical_op" = yes &&
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test "$lv_cv_gcc_wlogical_op_equal_expr_broken" = yes; then
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AC_DEFINE_UNQUOTED([BROKEN_GCC_WLOGICALOP_EQUAL_EXPR], 1,
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[Define to 1 if gcc -Wlogical-op reports false positive 'or' equal expr])
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fi
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])
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