--- /dev/null
+# warnings.m4 serial 6
+dnl Copyright (C) 2008-2012 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Simon Josefsson
+
+# gl_AS_VAR_APPEND(VAR, VALUE)
+# ----------------------------
+# Provide the functionality of AS_VAR_APPEND if Autoconf does not have it.
+m4_ifdef([AS_VAR_APPEND],
+[m4_copy([AS_VAR_APPEND], [gl_AS_VAR_APPEND])],
+[m4_define([gl_AS_VAR_APPEND],
+[AS_VAR_SET([$1], [AS_VAR_GET([$1])$2])])])
+
+
+# gl_WARN_ADD(PARAMETER, [VARIABLE = WARN_CFLAGS])
+# ------------------------------------------------
+# Adds parameter to WARN_CFLAGS if the compiler supports it. For example,
+# gl_WARN_ADD([-Wparentheses]).
+#
+# If VARIABLE is a variable name, AC_SUBST it.
+AC_DEFUN([gl_WARN_ADD],
+dnl FIXME: gl_Warn must be used unquoted until we can assume
+dnl autoconf 2.64 or newer.
+[AS_VAR_PUSHDEF([gl_Warn], [gl_cv_warn_[]_AC_LANG_ABBREV[]_$1])dnl
+AS_VAR_PUSHDEF([gl_Flags], [_AC_LANG_PREFIX[]FLAGS])dnl
+AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], m4_defn([gl_Warn]), [
+ gl_save_compiler_FLAGS="$gl_Flags"
+ gl_Flags="$gl_Flags $1"
+ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
+ [AS_VAR_SET(gl_Warn, [yes])],
+ [AS_VAR_SET(gl_Warn, [no])])
+ gl_Flags="$gl_save_compiler_FLAGS"
+])
+AS_VAR_IF(gl_Warn, [yes],
+ [gl_AS_VAR_APPEND(m4_if([$2], [], [[WARN_CFLAGS]], [[$2]]), [" $1"])])
+AS_VAR_POPDEF([gl_Flags])dnl
+AS_VAR_POPDEF([gl_Warn])dnl
+m4_ifval([$2], [AS_LITERAL_IF([$2], [AC_SUBST([$2])], [])])dnl
+])