diff --git a/m4/asmcfi.m4 b/m4/asmcfi.m4
index 3e286022..bf427a5a 100644
--- a/m4/asmcfi.m4
+++ b/m4/asmcfi.m4
@@ -1,13 +1,29 @@
+dnl ------------------------------------------------------------------
+dnl  Check whether the assembler understands .cfi_* pseudo-ops.
+dnl ------------------------------------------------------------------
 AC_DEFUN([GCC_AS_CFI_PSEUDO_OP],
-[AC_CACHE_CHECK([assembler .cfi pseudo-op support],
-    gcc_cv_as_cfi_pseudo_op, [
-    gcc_cv_as_cfi_pseudo_op=unknown
-    AC_TRY_COMPILE([asm (".cfi_sections\n\t.cfi_startproc\n\t.cfi_endproc");],,
-		   [gcc_cv_as_cfi_pseudo_op=yes],
-		   [gcc_cv_as_cfi_pseudo_op=no])
- ])
- if test "x$gcc_cv_as_cfi_pseudo_op" = xyes; then
-    AC_DEFINE(HAVE_AS_CFI_PSEUDO_OP, 1,
-	      [Define if your assembler supports .cfi_* directives.])
- fi
+[
+  AC_CACHE_CHECK([assembler .cfi pseudo-op support],
+                 [gcc_cv_as_cfi_pseudo_op],
+  [ AC_LANG_PUSH([C])
+    AC_COMPILE_IFELSE(
+      [AC_LANG_SOURCE([[
+        int foo (void)
+        {
+          __asm__ (
+            ".cfi_sections\n\t"
+            ".cfi_startproc\n\t"
+            ".cfi_endproc");
+          return 0;
+        }
+      ]])],
+      [gcc_cv_as_cfi_pseudo_op=yes],
+      [gcc_cv_as_cfi_pseudo_op=no])
+    AC_LANG_POP([C])
+  ])
+
+  if test "x$gcc_cv_as_cfi_pseudo_op" = xyes; then
+    AC_DEFINE([HAVE_AS_CFI_PSEUDO_OP], [1],
+              [Define if your assembler supports .cfi_* directives.])
+  fi
 ])
diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4
index bd753b34..54191c55 100644
--- a/m4/ax_check_compile_flag.m4
+++ b/m4/ax_check_compile_flag.m4
@@ -34,14 +34,24 @@
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 6
+#serial 11
 
 AC_DEFUN([AX_CHECK_COMPILE_FLAG],
 [AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
 AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
-AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
+AC_CACHE_CHECK([whether the _AC_LANG compiler accepts $1], CACHEVAR, [
   ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
-  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
+  if test x"m4_case(_AC_LANG,
+                     [C], [$GCC],
+                     [C++], [$GXX],
+                     [Fortran], [$GFC],
+                     [Fortran 77], [$G77],
+                     [Objective C], [$GOBJC],
+                     [Objective C++], [$GOBJCXX],
+                     [no])" = xyes ; then
+    add_gnu_werror="-Werror"
+  fi
+  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1 $add_gnu_werror"
   AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
     [AS_VAR_SET(CACHEVAR,[yes])],
     [AS_VAR_SET(CACHEVAR,[no])])