Sync toplevel with upstream GCC.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

config/gcc-plugin.m4

@@ -0,0 +1,113 @@
+# gcc-plugin.m4 -*- Autoconf -*-
+# Check whether GCC is able to be built with plugin support.
+
+dnl Copyright (C) 2014 Free Software Foundation, Inc.
+dnl This file is free software, distributed under the terms of the GNU
+dnl General Public License.  As a special exception to the GNU General
+dnl Public License, this file may be distributed as part of a program
+dnl that contains a configuration script generated by Autoconf, under
+dnl the same distribution terms as the rest of that program.
+
+# Check for plugin support.
+# Respects --enable-plugin.
+# Sets the shell variables enable_plugin and pluginlibs.
+AC_DEFUN([GCC_ENABLE_PLUGINS],
+  [# Check for plugin support
+   AC_ARG_ENABLE(plugin,
+   [AS_HELP_STRING([--enable-plugin], [enable plugin support])],
+   enable_plugin=$enableval,
+   enable_plugin=yes; default_plugin=yes)
+
+   pluginlibs=
+
+   case "${host}" in
+     *-*-darwin*)
+       if test x$build = x$host; then
+	 export_sym_check="nm${exeext} -g"
+       elif test x$host = x$target; then
+	 export_sym_check="$gcc_cv_nm -g"
+       else
+	 export_sym_check=
+       fi
+     ;;
+     *)
+       if test x$build = x$host; then
+	 export_sym_check="objdump${exeext} -T"
+       elif test x$host = x$target; then
+	 export_sym_check="$gcc_cv_objdump -T"
+       else
+	 export_sym_check=
+       fi
+     ;;
+   esac
+
+   if test x"$enable_plugin" = x"yes"; then
+
+     AC_MSG_CHECKING([for exported symbols])
+     if test "x$export_sym_check" != x; then
+       echo "int main() {return 0;} int foobar() {return 0;}" > conftest.c
+       ${CC} ${CFLAGS} ${LDFLAGS} conftest.c -o conftest$ac_exeext > /dev/null 2>&1
+       if $export_sym_check conftest$ac_exeext | grep -q foobar > /dev/null; then
+	 : # No need to use a flag
+	 AC_MSG_RESULT([yes])
+       else
+	 AC_MSG_RESULT([yes])
+	 AC_MSG_CHECKING([for -rdynamic])
+	 ${CC} ${CFLAGS} ${LDFLAGS} -rdynamic conftest.c -o conftest$ac_exeext > /dev/null 2>&1
+	 if $export_sym_check conftest$ac_exeext | grep -q foobar > /dev/null; then
+	   plugin_rdynamic=yes
+	   pluginlibs="-rdynamic"
+	 else
+	   plugin_rdynamic=no
+	   enable_plugin=no
+	 fi
+	 AC_MSG_RESULT([$plugin_rdynamic])
+       fi
+     else
+       AC_MSG_RESULT([unable to check])
+     fi
+
+     # Check -ldl
+     saved_LIBS="$LIBS"
+     AC_SEARCH_LIBS([dlopen], [dl])
+     if test x"$ac_cv_search_dlopen" = x"-ldl"; then
+       pluginlibs="$pluginlibs -ldl"
+     fi
+     LIBS="$saved_LIBS"
+
+     # Check that we can build shared objects with -fPIC -shared
+     saved_LDFLAGS="$LDFLAGS"
+     saved_CFLAGS="$CFLAGS"
+     case "${host}" in
+       *-*-darwin*)
+	 CFLAGS=`echo $CFLAGS | sed s/-mdynamic-no-pic//g`
+	 CFLAGS="$CFLAGS -fPIC"
+	 LDFLAGS="$LDFLAGS -shared -undefined dynamic_lookup"
+       ;;
+       *)
+	 CFLAGS="$CFLAGS -fPIC"
+	 LDFLAGS="$LDFLAGS -fPIC -shared"
+       ;;
+     esac
+     AC_MSG_CHECKING([for -fPIC -shared])
+     AC_TRY_LINK(
+       [extern int X;],[return X == 0;],
+       [AC_MSG_RESULT([yes]); have_pic_shared=yes],
+       [AC_MSG_RESULT([no]); have_pic_shared=no])
+     if test x"$have_pic_shared" != x"yes" -o x"$ac_cv_search_dlopen" = x"no"; then
+       pluginlibs=
+       enable_plugin=no
+     fi
+     LDFLAGS="$saved_LDFLAGS"
+     CFLAGS="$saved_CFLAGS"
+
+     # If plugin support had been requested but not available, fail.
+     if test x"$enable_plugin" = x"no" ; then
+       if test x"$default_plugin" != x"yes"; then
+	 AC_MSG_ERROR([
+   Building GCC with plugin support requires a host that supports
+   -fPIC, -shared, -ldl and -rdynamic.])
+       fi
+     fi
+   fi
+])