configure: Enable set of standard -Werror=foo flags

We're not going to depend on gnome-common (I assume) so this patch
nicks the systemd macro to test for compiler flags, and uses it to set
a similar set of -Werror=foo as the gnome-common one does.

See https://bugzilla.gnome.org/show_bug.cgi?id=608953
See https://mail.gnome.org/archives/desktop-devel-list/2012-July/msg00100.html

If we're going to be setting more strict compiler flags for GNOME, we
should really ensure GLib builds with them first, as it's kind of the
model citizen.

In particular, you can see several times that downstreams such as
Debian have come in and fixed -Wformat-security bugs.  We should never
let those get into tarballs, or even commits.

https://bugzilla.gnome.org/show_bug.cgi?id=687385

1 files changed, 288 insertions, 0 deletions

diff --git a/m4macros/attributes.m4 b/m4macros/attributes.m4
new file mode 100644
index 000000000..f0bcf2421
--- /dev/null
+++ b/m4macros/attributes.m4
@@ -0,0 +1,288 @@
+dnl Macros to check the presence of generic (non-typed) symbols.
+dnl Copyright (c) 2006-2008 Diego Pettenò <flameeyes@gmail.com>
+dnl Copyright (c) 2006-2008 xine project
+dnl Copyright (c) 2012 Lucas De Marchi <lucas.de.marchi@gmail.com>
+dnl
+dnl This program is free software; you can redistribute it and/or modify
+dnl it under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation; either version 2, or (at your option)
+dnl any later version.
+dnl
+dnl This program is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+dnl GNU General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with this program; if not, write to the Free Software
+dnl Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+dnl 02110-1301, USA.
+dnl
+dnl As a special exception, the copyright owners of the
+dnl macro gives unlimited permission to copy, distribute and modify the
+dnl configure scripts that are the output of Autoconf when processing the
+dnl Macro. You need not follow the terms of the GNU General Public
+dnl License when using or distributing such scripts, even though portions
+dnl of the text of the Macro appear in them. The GNU General Public
+dnl License (GPL) does govern all other use of the material that
+dnl constitutes the Autoconf Macro.
+dnl
+dnl This special exception to the GPL applies to versions of the
+dnl Autoconf Macro released by this project. When you make and
+dnl distribute a modified version of the Autoconf Macro, you may extend
+dnl this special exception to the GPL to apply to your modified version as
+dnl well.
+
+dnl Check if FLAG in ENV-VAR is supported by compiler and append it
+dnl to WHERE-TO-APPEND variable
+dnl CC_CHECK_FLAG_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG])
+
+AC_DEFUN([CC_CHECK_FLAG_APPEND], [
+  AC_CACHE_CHECK([if $CC supports flag $3 in envvar $2],
+                 AS_TR_SH([cc_cv_$2_$3]),
+		 [eval "AS_TR_SH([cc_save_$2])='${$2}'"
+		  eval "AS_TR_SH([$2])='-Werror $3'"
+		  AC_COMPILE_IFELSE([AC_LANG_SOURCE([int a = 0; int main(void) { return a; } ])],
+                                    [eval "AS_TR_SH([cc_cv_$2_$3])='yes'"],
+                                    [eval "AS_TR_SH([cc_cv_$2_$3])='no'"])
+		  eval "AS_TR_SH([$2])='$cc_save_$2'"])
+
+  AS_IF([eval test x$]AS_TR_SH([cc_cv_$2_$3])[ = xyes],
+        [eval "$1='${$1} $3'"])
+])
+
+dnl CC_CHECK_FLAGS_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG1 FLAG2])
+AC_DEFUN([CC_CHECK_FLAGS_APPEND], [
+  for flag in $3; do
+    CC_CHECK_FLAG_APPEND($1, $2, $flag)
+  done
+])
+
+dnl Check if the flag is supported by linker (cacheable)
+dnl CC_CHECK_LDFLAGS([FLAG], [ACTION-IF-FOUND],[ACTION-IF-NOT-FOUND])
+
+AC_DEFUN([CC_CHECK_LDFLAGS], [
+  AC_CACHE_CHECK([if $CC supports $1 flag],
+    AS_TR_SH([cc_cv_ldflags_$1]),
+    [ac_save_LDFLAGS="$LDFLAGS"
+     LDFLAGS="$LDFLAGS $1"
+     AC_LINK_IFELSE([int main() { return 1; }],
+       [eval "AS_TR_SH([cc_cv_ldflags_$1])='yes'"],
+       [eval "AS_TR_SH([cc_cv_ldflags_$1])="])
+     LDFLAGS="$ac_save_LDFLAGS"
+    ])
+
+  AS_IF([eval test x$]AS_TR_SH([cc_cv_ldflags_$1])[ = xyes],
+    [$2], [$3])
+])
+
+dnl define the LDFLAGS_NOUNDEFINED variable with the correct value for
+dnl the current linker to avoid undefined references in a shared object.
+AC_DEFUN([CC_NOUNDEFINED], [
+  dnl We check $host for which systems to enable this for.
+  AC_REQUIRE([AC_CANONICAL_HOST])
+
+  case $host in
+     dnl FreeBSD (et al.) does not complete linking for shared objects when pthreads
+     dnl are requested, as different implementations are present; to avoid problems
+     dnl use -Wl,-z,defs only for those platform not behaving this way.
+     *-freebsd* | *-openbsd*) ;;
+     *)
+        dnl First of all check for the --no-undefined variant of GNU ld. This allows
+        dnl for a much more readable commandline, so that people can understand what
+        dnl it does without going to look for what the heck -z defs does.
+        for possible_flags in "-Wl,--no-undefined" "-Wl,-z,defs"; do
+          CC_CHECK_LDFLAGS([$possible_flags], [LDFLAGS_NOUNDEFINED="$possible_flags"])
+	  break
+        done
+	;;
+  esac
+
+  AC_SUBST([LDFLAGS_NOUNDEFINED])
+])
+
+dnl Check for a -Werror flag or equivalent. -Werror is the GCC
+dnl and ICC flag that tells the compiler to treat all the warnings
+dnl as fatal. We usually need this option to make sure that some
+dnl constructs (like attributes) are not simply ignored.
+dnl
+dnl Other compilers don't support -Werror per se, but they support
+dnl an equivalent flag:
+dnl  - Sun Studio compiler supports -errwarn=%all
+AC_DEFUN([CC_CHECK_WERROR], [
+  AC_CACHE_CHECK(
+    [for $CC way to treat warnings as errors],
+    [cc_cv_werror],
+    [CC_CHECK_CFLAGS_SILENT([-Werror], [cc_cv_werror=-Werror],
+      [CC_CHECK_CFLAGS_SILENT([-errwarn=%all], [cc_cv_werror=-errwarn=%all])])
+    ])
+])
+
+AC_DEFUN([CC_CHECK_ATTRIBUTE], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([if $CC supports __attribute__(( ifelse([$2], , [$1], [$2]) ))],
+    AS_TR_SH([cc_cv_attribute_$1]),
+    [ac_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     AC_COMPILE_IFELSE([AC_LANG_SOURCE([$3])],
+       [eval "AS_TR_SH([cc_cv_attribute_$1])='yes'"],
+       [eval "AS_TR_SH([cc_cv_attribute_$1])='no'"])
+     CFLAGS="$ac_save_CFLAGS"
+    ])
+
+  AS_IF([eval test x$]AS_TR_SH([cc_cv_attribute_$1])[ = xyes],
+    [AC_DEFINE(
+       AS_TR_CPP([SUPPORT_ATTRIBUTE_$1]), 1,
+         [Define this if the compiler supports __attribute__(( ifelse([$2], , [$1], [$2]) ))]
+         )
+     $4],
+    [$5])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_CONSTRUCTOR], [
+  CC_CHECK_ATTRIBUTE(
+    [constructor],,
+    [void __attribute__((constructor)) ctor() { int a; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_FORMAT], [
+  CC_CHECK_ATTRIBUTE(
+    [format], [format(printf, n, n)],
+    [void __attribute__((format(printf, 1, 2))) printflike(const char *fmt, ...) { fmt = (void *)0; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_FORMAT_ARG], [
+  CC_CHECK_ATTRIBUTE(
+    [format_arg], [format_arg(printf)],
+    [char *__attribute__((format_arg(1))) gettextlike(const char *fmt) { fmt = (void *)0; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_VISIBILITY], [
+  CC_CHECK_ATTRIBUTE(
+    [visibility_$1], [visibility("$1")],
+    [void __attribute__((visibility("$1"))) $1_function() { }],
+    [$2], [$3])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_NONNULL], [
+  CC_CHECK_ATTRIBUTE(
+    [nonnull], [nonnull()],
+    [void __attribute__((nonnull())) some_function(void *foo, void *bar) { foo = (void*)0; bar = (void*)0; }],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_UNUSED], [
+  CC_CHECK_ATTRIBUTE(
+    [unused], ,
+    [void some_function(void *foo, __attribute__((unused)) void *bar);],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_SENTINEL], [
+  CC_CHECK_ATTRIBUTE(
+    [sentinel], ,
+    [void some_function(void *foo, ...) __attribute__((sentinel));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_DEPRECATED], [
+  CC_CHECK_ATTRIBUTE(
+    [deprecated], ,
+    [void some_function(void *foo, ...) __attribute__((deprecated));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_ALIAS], [
+  CC_CHECK_ATTRIBUTE(
+    [alias], [weak, alias],
+    [void other_function(void *foo) { }
+     void some_function(void *foo) __attribute__((weak, alias("other_function")));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_MALLOC], [
+  CC_CHECK_ATTRIBUTE(
+    [malloc], ,
+    [void * __attribute__((malloc)) my_alloc(int n);],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_PACKED], [
+  CC_CHECK_ATTRIBUTE(
+    [packed], ,
+    [struct astructure { char a; int b; long c; void *d; } __attribute__((packed));],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_CONST], [
+  CC_CHECK_ATTRIBUTE(
+    [const], ,
+    [int __attribute__((const)) twopow(int n) { return 1 << n; } ],
+    [$1], [$2])
+])
+
+AC_DEFUN([CC_FLAG_VISIBILITY], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([if $CC supports -fvisibility=hidden],
+    [cc_cv_flag_visibility],
+    [cc_flag_visibility_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     CC_CHECK_CFLAGS_SILENT([-fvisibility=hidden],
+	cc_cv_flag_visibility='yes',
+	cc_cv_flag_visibility='no')
+     CFLAGS="$cc_flag_visibility_save_CFLAGS"])
+
+  AS_IF([test "x$cc_cv_flag_visibility" = "xyes"],
+    [AC_DEFINE([SUPPORT_FLAG_VISIBILITY], 1,
+       [Define this if the compiler supports the -fvisibility flag])
+     $1],
+    [$2])
+])
+
+AC_DEFUN([CC_FUNC_EXPECT], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([if compiler has __builtin_expect function],
+    [cc_cv_func_expect],
+    [ac_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     AC_COMPILE_IFELSE([AC_LANG_SOURCE(
+       [int some_function() {
+        int a = 3;
+        return (int)__builtin_expect(a, 3);
+	}])],
+       [cc_cv_func_expect=yes],
+       [cc_cv_func_expect=no])
+     CFLAGS="$ac_save_CFLAGS"
+    ])
+
+  AS_IF([test "x$cc_cv_func_expect" = "xyes"],
+    [AC_DEFINE([SUPPORT__BUILTIN_EXPECT], 1,
+     [Define this if the compiler supports __builtin_expect() function])
+     $1],
+    [$2])
+])
+
+AC_DEFUN([CC_ATTRIBUTE_ALIGNED], [
+  AC_REQUIRE([CC_CHECK_WERROR])
+  AC_CACHE_CHECK([highest __attribute__ ((aligned ())) supported],
+    [cc_cv_attribute_aligned],
+    [ac_save_CFLAGS="$CFLAGS"
+     CFLAGS="$CFLAGS $cc_cv_werror"
+     for cc_attribute_align_try in 64 32 16 8 4 2; do
+        AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+          int main() {
+            static char c __attribute__ ((aligned($cc_attribute_align_try))) = 0;
+            return c;
+          }])], [cc_cv_attribute_aligned=$cc_attribute_align_try; break])
+     done
+     CFLAGS="$ac_save_CFLAGS"
+  ])
+
+  if test "x$cc_cv_attribute_aligned" != "x"; then
+     AC_DEFINE_UNQUOTED([ATTRIBUTE_ALIGNED_MAX], [$cc_cv_attribute_aligned],
+       [Define the highest alignment supported])
+  fi
+])