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 <stddef.h>

        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 <string.h>

        ]], [[

        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

])