# HG changeset patch
# User Eric Blake <eblake@redhat.com>
# Date 1376595955 21600
# Node ID 88b6cb053cd7e90b4b67cd598830cd647c971779
# Parent  1175d52f956a98ef5e9a819842e51fdfc38285cb
warnings: minor optimization

Paul Eggert suggested that expr is more efficient than echo|sed.

* m4/warnings.m4 (gl_COMPILER_OPTION_IF): Use fewer processes.

Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2013-08-15  Eric Blake  <eblake@redhat.com>
 
+	warnings: minor optimization
+	* m4/warnings.m4 (gl_COMPILER_OPTION_IF): Use fewer processes.
+
 	warnings: check -Wfoo rather than -Wno-foo
 	* m4/warnings.m4 (gl_COMPILER_OPTION_IF): If name begins with
 	-Wno-, test if the compiler recognizes the positive form instead.
diff --git a/m4/warnings.m4 b/m4/warnings.m4
--- a/m4/warnings.m4
+++ b/m4/warnings.m4
@@ -1,4 +1,4 @@
-# warnings.m4 serial 9
+# warnings.m4 serial 10
 dnl Copyright (C) 2008-2013 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -29,7 +29,7 @@
   [m4_pushdef([gl_Positive], m4_bpatsubst([$1], [^-Wno-], [-W]))],
   [gl_positive="$1"
 case $gl_positive in
-  -Wno-*) gl_positive=`echo ".$gl_positive" | sed 's/^.//; s/^-Wno-/-W/'`;;
+  -Wno-*) gl_positive=-W`expr "X$gl_positive" : 'X-Wno-\(.*\)'` ;;
 esac
 m4_pushdef([gl_Positive], [$gl_positive])])dnl
 AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], m4_defn([gl_Warn]), [