[json-glib] [build] Add AS_COMPILER_FLAGS

[Emmanuele Bassi <ebassi src gnome org>]

commit 3ddeb7a8779a4c51453289aa15af130af480eea6
Author: Emmanuele Bassi <ebassi linux intel com>
Date:   Tue Jun 9 11:24:54 2009 +0100

    [build] Add AS_COMPILER_FLAGS
    
    Use the m4 AS_COMPILER_FLAGS macro to check for the maintainer
    compiler flags supported by the C compiler. This should allow the
    build to handle gracefully different versions of GCC.
---
 .gitignore                          |    1 +
 Makefile.am                         |    2 +
 build/autotools/Makefile.am         |    2 +-
 build/autotools/as-compiler-flag.m4 |   62 +++++++++++++++++++++++++++++++++++
 configure.ac                        |    5 ++-
 5 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index 7963496..048ec7b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@ aclocal.m4
 autom4te.cache
 /build/autotools/*.m4
 !/build/autotools/shave.m4
+!/build/autotools/as-compiler-flag.m4
 configure
 config.guess
 config.h
diff --git a/Makefile.am b/Makefile.am
index d06623f..88aea79 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,5 +1,7 @@
 include $(top_srcdir)/Makefile.decl
 
+ACLOCAL_AMFLAGS = -I build/autotools
+
 SUBDIRS = json-glib doc
 
 if ENABLE_GLIB_TEST
diff --git a/build/autotools/Makefile.am b/build/autotools/Makefile.am
index a17717f..899cbc9 100644
--- a/build/autotools/Makefile.am
+++ b/build/autotools/Makefile.am
@@ -1,3 +1,3 @@
-EXTRA_DIST = shave-libtool.in shave.in shave.m4
+EXTRA_DIST = shave-libtool.in shave.in shave.m4 as-compiler-flag.m4
 
 DISTCLEANFILES = shave-libtool shave
diff --git a/build/autotools/as-compiler-flag.m4 b/build/autotools/as-compiler-flag.m4
new file mode 100644
index 0000000..0f660cf
--- /dev/null
+++ b/build/autotools/as-compiler-flag.m4
@@ -0,0 +1,62 @@
+dnl as-compiler-flag.m4 0.1.0
+
+dnl autostars m4 macro for detection of compiler flags
+
+dnl David Schleef <ds schleef org>
+
+dnl $Id: as-compiler-flag.m4,v 1.1 2005/12/15 23:35:19 ds Exp $
+
+dnl AS_COMPILER_FLAG(CFLAGS, ACTION-IF-ACCEPTED, [ACTION-IF-NOT-ACCEPTED])
+dnl Tries to compile with the given CFLAGS.
+dnl Runs ACTION-IF-ACCEPTED if the compiler can compile with the flags,
+dnl and ACTION-IF-NOT-ACCEPTED otherwise.
+
+AC_DEFUN([AS_COMPILER_FLAG],
+[
+  AC_MSG_CHECKING([to see if compiler understands $1])
+
+  save_CFLAGS="$CFLAGS"
+  CFLAGS="$CFLAGS $1"
+
+  AC_TRY_COMPILE([ ], [], [flag_ok=yes], [flag_ok=no])
+  CFLAGS="$save_CFLAGS"
+
+  if test "X$flag_ok" = Xyes ; then
+    m4_ifvaln([$2],[$2])
+    true
+  else
+    m4_ifvaln([$3],[$3])
+    true
+  fi
+  AC_MSG_RESULT([$flag_ok])
+])
+
+dnl AS_COMPILER_FLAGS(VAR, FLAGS)
+dnl Tries to compile with the given CFLAGS.
+
+AC_DEFUN([AS_COMPILER_FLAGS],
+[
+  list=$2
+  flags_supported=""
+  flags_unsupported=""
+  AC_MSG_CHECKING([for supported compiler flags])
+  for each in $list
+  do
+    save_CFLAGS="$CFLAGS"
+    CFLAGS="$CFLAGS $each"
+    AC_TRY_COMPILE([ ], [], [flag_ok=yes], [flag_ok=no])
+    CFLAGS="$save_CFLAGS"
+
+    if test "X$flag_ok" = Xyes ; then
+      flags_supported="$flags_supported $each"
+    else
+      flags_unsupported="$flags_unsupported $each"
+    fi
+  done
+  AC_MSG_RESULT([$flags_supported])
+  if test "X$flags_unsupported" != X ; then
+    AC_MSG_WARN([unsupported compiler flags: $flags_unsupported])
+  fi
+  $1="$$1 $flags_supported"
+])
+
diff --git a/configure.ac b/configure.ac
index 1d3e939..ef2d166 100644
--- a/configure.ac
+++ b/configure.ac
@@ -108,7 +108,10 @@ AC_ARG_ENABLE([maintainer-flags],
 
 AS_IF([test "x$enable_maintainer_flags" = "xyes" && test "x$GCC" = "xyes"],
       [
-        MAINTAINER_CFLAGS="-Werror -Wall -Wshadow -Wcast-align -Wno-uninitialized -Wformat-security -Winit-self"
+        AS_COMPILER_FLAGS([MAINTAINER_CFLAGS],
+                          ["-Werror -Wall -Wshadow -Wcast-align
+                            -Wno-uninitialized -Wformat-security
+                            -Winit-self -Wempty-body"])
       ]
 )