[gnome-common] Add lots of warnings to GNOME_COMPILE_WARNINGS

[David King <davidk src gnome org>]

commit e42ca9bec9d83aa53d7f79c480daf4b7c4d95fe1
Author: David King <amigadave amigadave com>
Date:   Sat Jul 28 15:19:55 2012 +0100

    Add lots of warnings to GNOME_COMPILE_WARNINGS
    
    Following Colin Walters' thread on desktop-devel-list:
    
    https://mail.gnome.org/archives/desktop-devel-list/2012-July/msg00100.html
    
    Add a selection of more strict warnings to the default level of
    GNOME_COMPILE_WARNINGS. Check all the warnings by passing them to GCC,
    and ignore those which fail. Set the severity of some of the warnings to
    errors, so that particularly bad code is rejected (set the warning level
    to âminimumâ is you wish to avoid this behaviour). Fixes bug 568546 and
    bug 608953.

 macros2/gnome-compiler-flags.m4 |   54 ++++++++++++++++++++------------------
 1 files changed, 28 insertions(+), 26 deletions(-)
---
diff --git a/macros2/gnome-compiler-flags.m4 b/macros2/gnome-compiler-flags.m4
index b9db2fd..1dbfa1a 100644
--- a/macros2/gnome-compiler-flags.m4
+++ b/macros2/gnome-compiler-flags.m4
@@ -1,5 +1,6 @@
 dnl GNOME_COMPILE_WARNINGS
-dnl Turn on many useful compiler warnings
+dnl Turn on many useful compiler warnings and substitute the result into
+dnl WARN_CFLAGS
 dnl For now, only works on GCC
 AC_DEFUN([GNOME_COMPILE_WARNINGS],[
     dnl ******************************
@@ -11,7 +12,6 @@ AC_DEFUN([GNOME_COMPILE_WARNINGS],[
                                  [Turn on compiler warnings]),,
                   [enable_compile_warnings="m4_default([$1],[yes])"])
 
-    warnCFLAGS=
     if test "x$GCC" != xyes; then
 	enable_compile_warnings=no
     fi
@@ -27,38 +27,40 @@ AC_DEFUN([GNOME_COMPILE_WARNINGS],[
 	warning_flags="-Wall"
 	;;
     yes)
-	warning_flags="-Wall -Wmissing-prototypes"
+	warning_flags="-Wall -Wstrict-prototypes -Waggregate-return -Werror=missing-prototypes -Werror=implicit-function-declaration -Werror=pointer-arith -Werror=init-self -Werror=format-security -Werror=format=2 -Werror=missing-include-dirs"
 	;;
     maximum|error)
-	warning_flags="-Wall -Wmissing-prototypes -Wnested-externs -Wpointer-arith"
-	CFLAGS="$warning_flags $CFLAGS"
-	for option in -Wno-sign-compare; do
-		SAVE_CFLAGS="$CFLAGS"
-		CFLAGS="$CFLAGS $option"
-		AC_MSG_CHECKING([whether gcc understands $option])
-		AC_TRY_COMPILE([], [],
-			has_option=yes,
-			has_option=no,)
-		CFLAGS="$SAVE_CFLAGS"
-		AC_MSG_RESULT($has_option)
-		if test $has_option = yes; then
-		  warning_flags="$warning_flags $option"
-		fi
-		unset has_option
-		unset SAVE_CFLAGS
-	done
-	unset option
-	if test "$enable_compile_warnings" = "error" ; then
-	    warning_flags="$warning_flags -Werror"
-	fi
+	warning_flags="-Wall -Wstrict-prototypes -Waggregate-return -Wdeclaration-after-statement -Werror=missing-prototypes -Werror=implicit-function-declaration -Werror=pointer-arith -Werror=init-self -Werror=format-security -Werror=format=2 -Werror=missing-include-dirs -Wnested-externs -Wno-sign-compare"
 	;;
     *)
 	AC_MSG_ERROR(Unknown argument '$enable_compile_warnings' to --enable-compile-warnings)
 	;;
     esac
+
+    if test "$enable_compile_warnings" = "error" ; then
+        warning_flags="$warning_flags -Werror"
+    fi
+
+    dnl Check whether GCC supports the warning options
+    for option in $warning_flags; do
+	save_CFLAGS="$CFLAGS"
+	CFLAGS="$CFLAGS $option"
+	AC_MSG_CHECKING([whether gcc understands $option])
+	AC_TRY_COMPILE([], [],
+	    has_option=yes,
+	    has_option=no,)
+	CFLAGS="$save_CFLAGS"
+	AC_MSG_RESULT([$has_option])
+	if test $has_option = yes; then
+	    tested_warning_flags="$tested_warning_flags $option"
+	fi
+	unset has_option
+	unset save_CFLAGS
+    done
+    unset option
     CFLAGS="$realsave_CFLAGS"
     AC_MSG_CHECKING(what warning flags to pass to the C compiler)
-    AC_MSG_RESULT($warning_flags)
+    AC_MSG_RESULT($tested_warning_flags)
 
     AC_ARG_ENABLE(iso-c,
                   AC_HELP_STRING([--enable-iso-c],
@@ -81,7 +83,7 @@ AC_DEFUN([GNOME_COMPILE_WARNINGS],[
     fi
     AC_MSG_RESULT($complCFLAGS)
 
-    WARN_CFLAGS="$warning_flags $complCFLAGS"
+    WARN_CFLAGS="$tested_warning_flags $complCFLAGS"
     AC_SUBST(WARN_CFLAGS)
 ])