Enable all warnings permanently & default to -Werror for GIT builds

Given that we auto-detect whether each -Wxxxx flag is supported by
GCC, and we are warning-free and use automake silent rules, there
is no compelling reason to allow compile warnings to be disabled.

Replace the --enable-compile-warnings flag with a simpler
--enable-werror flag, which defaults to 'yes' if building
from GIT, or 'no' if building from tar.gz

This helps ensure that everyone writing patches for libvirt will
take care to fix their warning problems before submitting for
review

* autobuild.sh: Force -Werror
* configure.ac: Update for LIBVIRT_COMPILE_WARNINGS macro change
* m4/virt-compile-warnings.m4: Permanently enable all warnings,
  auto-enable Werror for GIT builds

1 files changed, 126 insertions, 132 deletions

diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4
index 3a428c32b..5527bff50 100644
--- a/m4/virt-compile-warnings.m4
+++ b/m4/virt-compile-warnings.m4
@@ -7,139 +7,133 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
     dnl More compiler warnings
     dnl ******************************
 
-    AC_ARG_ENABLE(compile-warnings,
-                  [AC_HELP_STRING([--enable-compile-warnings=@<:@no/yes/error@:>@],
-                                 [Turn on compiler warnings])],,
-                  [enable_compile_warnings="m4_default([$1],[yes])"])
-
-    case "$enable_compile_warnings" in
-    no)
-        try_compiler_flags=""
-        ;;
-    yes|minimum|maximum|error)
-
-        # 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="$dontwarn -Wformat-nonliteral"
-
-        # We might fundamentally need some of these disabled forever, but
-        # ideally we'd turn many of them on
-        dontwarn="$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.
-        gl_WARN_ADD([-Wno-format-nonliteral])
-
-        # 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.])
-        AC_DEFINE([_FORTIFY_SOURCE], [2],
-          [enable compile-time and run-time bounds-checking, and some warnings])
-
-        # Extra special flags
-        dnl -fstack-protector stuff passes gl_WARN_ADD with gcc
-        dnl on Mingw32, but fails when actually used
-        case $host in
-           *-*-linux*)
-           dnl Fedora only uses -fstack-protector, but doesn't seem to
-           dnl be great overhead in adding -fstack-protector-all instead
-           dnl gl_WARN_ADD([-fstack-protector])
-           gl_WARN_ADD([-fstack-protector-all])
-           gl_WARN_ADD([--param=ssp-buffer-size=4])
-           ;;
-        esac
-        gl_WARN_ADD([-fexceptions])
-        gl_WARN_ADD([-fasynchronous-unwind-tables])
-        gl_WARN_ADD([-fdiagnostics-show-option])
-        gl_WARN_ADD([-funit-at-a-time])
-
-        # Need -fipa-pure-const in order to make -Wsuggest-attribute=pure
-        # fire even without -O.
-        gl_WARN_ADD([-fipa-pure-const])
-        # We should eventually enable this, but right now there are at
-        # least 75 functions triggering warnings.
-        gl_WARN_ADD([-Wno-suggest-attribute=pure])
-        gl_WARN_ADD([-Wno-suggest-attribute=const])
-
-        if test "$enable_compile_warnings" = "error"
-        then
-          gl_WARN_ADD([-Werror])
-        fi
-        ;;
-    *)
-        AC_MSG_ERROR(Unknown argument '$enable_compile_warnings' to --enable-compile-warnings)
-        ;;
+    AC_ARG_ENABLE([werror],
+                  AS_HELP_STRING([--enable-werror], [Use -Werror (if supported)]),
+                  [set_werror="$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"
+
+    # 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.
+    gl_WARN_ADD([-Wno-format-nonliteral])
+
+    # 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.])
+    AC_DEFINE([_FORTIFY_SOURCE], [2],
+      [enable compile-time and run-time bounds-checking, and some warnings])
+
+    # 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])