1 files changed, 20 insertions, 0 deletions
diff --git a/m4/acinclude.m4 b/m4/acinclude.m4
index df4f83a4..8ea45973 100644
--- a/m4/acinclude.m4
+++ b/m4/acinclude.m4
@@ -101,6 +101,26 @@ AC_DEFUN([GCC_GNU89_INLINE_CC],[
   fi
 ])
 
+dnl CFLAGS_ADD(PARAMETER, VARIABLE)
+dnl Adds parameter to VARIABLE if the compiler supports it.  For example,
+dnl CFLAGS_ADD([-Wall],[WARN_FLAGS]).
+AC_DEFUN([CFLAGS_ADD],
+[AS_VAR_PUSHDEF([my_cflags], [cflags_cv_warn_$1])dnl
+AC_CACHE_CHECK([whether compiler handles $1], [my_cflags], [
+  save_CFLAGS="$CFLAGS"
+  CFLAGS="${CFLAGS} $1"
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
+                    [AS_VAR_SET([my_cflags], [yes])],
+                    [AS_VAR_SET([my_cflags], [no])])
+  CFLAGS="$save_CFLAGS"
+])
+AS_VAR_PUSHDEF([new_cflags], [[$2]])dnl
+AS_VAR_IF([my_cflags], [yes], [AS_VAR_APPEND([new_cflags], [" $1"])])
+AS_VAR_POPDEF([new_cflags])dnl
+AS_VAR_POPDEF([my_cflags])dnl
+m4_ifval([$2], [AS_LITERAL_IF([$2], [AC_SUBST([$2])], [])])dnl
+])
+
 dnl Checks for getmntinfo and determines whether it uses statfs or statvfs
 AC_DEFUN([FS_STATS_TYPE],
   [AC_CACHE_CHECK([filesystem statistics type], fs_stats_cv_type,