should _GNU_SOURCE be used in libiberty if glibc is present?

[Rafael Ávila de Espíndola <rafael dot espindola at gmail dot com>]

I noticed that in the config.h generated for libiberty has HAVE_DECL_ASPRINTF  
defined as 0. This hapens because _GNU_SOURCE is not used when running the 
test programs.

Coping the test that enables _GNU_SOURCE from gcc/configure.ac to 
libiberty/configure.ac results in HAVE_DECL_ASPRINTF  being defined as 1. I 
am not sure where in libiberty/configure.ac should the test be added (if it 
should). Is the attached patch correct? If so, I will submit a formal patch 
to gcc-patches.

I am currently bootstraping the trunk with the patch applied.

Thanks,
Rafael

Index: libiberty/configure.ac
===================================================================
--- libiberty/configure.ac	(revision 107446)
+++ libiberty/configure.ac	(working copy)
@@ -227,6 +227,21 @@ AC_SUBST_FILE(host_makefile_frag)
 # It's OK to check for header files.  Although the compiler may not be
 # able to link anything, it had better be able to at least compile
 # something.
+
+AC_MSG_CHECKING(for GNU C library)
+AC_CACHE_VAL(gcc_cv_glibc,
+[AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+  [[#include <features.h>]], [[
+#if ! (defined __GLIBC__ || defined __GNU_LIBRARY__)
+#error Not a GNU C library system
+#endif]])],
+  [gcc_cv_glibc=yes],
+  [gcc_cv_glibc=no])])
+AC_MSG_RESULT($gcc_cv_glibc)
+if test $gcc_cv_glibc = yes; then
+  AC_DEFINE(_GNU_SOURCE, 1, [Always define this when using the GNU C Library])
+fi
+
 AC_CHECK_HEADERS(sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h)
 AC_HEADER_SYS_WAIT
 AC_HEADER_TIME
Index: libiberty/configure
===================================================================
--- libiberty/configure	(revision 107446)
+++ libiberty/configure	(working copy)
@@ -3594,6 +3594,71 @@ host_makefile_frag=${frag}
 # able to link anything, it had better be able to at least compile
 # something.
 
+echo "$as_me:$LINENO: checking for GNU C library" >&5
+echo $ECHO_N "checking for GNU C library... $ECHO_C" >&6
+if test "${gcc_cv_glibc+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+#include <features.h>
+int
+main ()
+{
+
+#if ! (defined __GLIBC__ || defined __GNU_LIBRARY__)
+#error Not a GNU C library system
+#endif
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag"			 || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  gcc_cv_glibc=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+gcc_cv_glibc=no
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+
+echo "$as_me:$LINENO: result: $gcc_cv_glibc" >&5
+echo "${ECHO_T}$gcc_cv_glibc" >&6
+if test $gcc_cv_glibc = yes; then
+
+cat >>confdefs.h <<\_ACEOF
+#define _GNU_SOURCE 1
+_ACEOF
+
+fi
+
+
 
 
 
@@ -6424,18 +6489,24 @@ else
   ac_cv_func_fork_works=cross
 else
   cat >conftest.$ac_ext <<_ACEOF
-/* By Ruediger Kuhlmann. */
-      #include <sys/types.h>
-      #if HAVE_UNISTD_H
-      # include <unistd.h>
-      #endif
-      /* Some systems only have a dummy stub for fork() */
-      int main ()
-      {
-	if (fork() < 0)
-	  exit (1);
-	exit (0);
-      }
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+$ac_includes_default
+int
+main ()
+{
+
+	  /* By Ruediger Kuhlmann. */
+	  if (fork() < 0)
+	    exit (1);
+	  exit (0);
+
+  ;
+  return 0;
+}
 _ACEOF
 rm -f conftest$ac_exeext
 if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5

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