Eliminate 'extension used' clang warning in sparc_mach_dep.S (configure)

A number of .S (asm) files to be compiled when targeting sparc.
Option -Wno-language-extension-token should be passed to clang to
suppress a warning about passing asm files to the compiler.

* configure.ac (compile_asm): New variable.
* configure.ac [$host==sparc-*] (compile_asm): Set to true.
* configure.ac [$compile_asm==true && $GCC==yes]
(ac_cv_lang_ext_token): Set to yes if compiler supports -Werror and
-Wno-language-extension-token options.
* configure.ac [$compile_asm==true && $ac_cv_lang_ext_token==yes
&& $GCC==yes] (CFLAGS): Append -Wno-language-extension-token.

1 files changed, 18 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 88f85d9f..2a9e3898 100644
--- a/configure.ac
+++ b/configure.ac
@@ -190,6 +190,7 @@ CFLAGS="$old_CFLAGS"
 
 THREADDLLIBS=
 need_atomic_ops_asm=false
+compile_asm=false
 use_parallel_mark=no
 use_thread_local_alloc=no
 # Libraries needed to support dynamic loading and/or threads.
@@ -590,17 +591,21 @@ case "$host" in
     ;;
  sparc-*-netbsd*)
     machdep="sparc_netbsd_mach_dep.lo"
+    compile_asm=true
     ;;
  sparc*-*-linux* | sparc*-*-openbsd* | sparc64-*-freebsd* | sparc64-*-netbsd*)
     machdep="sparc_mach_dep.lo"
+    compile_asm=true
     ;;
  sparc-sun-solaris2.3)
     machdep="sparc_mach_dep.lo"
+    compile_asm=true
     AC_DEFINE(SUNOS53_SHARED_LIB, 1,
               [Define to work around a Solaris 5.3 bug (see dyn_load.c).])
     ;;
  sparc*-sun-solaris2*)
     machdep="sparc_mach_dep.lo"
+    compile_asm=true
     ;;
  ia64-*-*)
     machdep="ia64_save_regs_in_stack.lo"
@@ -611,6 +616,19 @@ addobjs="$addobjs $machdep"
 AC_SUBST(addobjs)
 AC_SUBST(addlibs)
 
+# Suppress "extension used" clang warning (when compiling .S files).
+if test x$compile_asm = xtrue -a "$GCC" = yes; then
+  AC_MSG_CHECKING([whether compiler supports -Wno-language-extension-token])
+  old_CFLAGS="$CFLAGS"
+  CFLAGS="$CFLAGS -Werror -Wno-language-extension-token"
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
+                    [ac_cv_lang_ext_token=yes], [ac_cv_lang_ext_token=no])
+  CFLAGS="$old_CFLAGS"
+  AS_IF([test "$ac_cv_lang_ext_token" = yes],
+        [CFLAGS="$CFLAGS -Wno-language-extension-token"])
+  AC_MSG_RESULT($ac_cv_lang_ext_token)
+fi
+
 dnl We use these options to decide which functions to include.
 AC_ARG_WITH(target-subdir,
 [  --with-target-subdir=SUBDIR