X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Falloca.m4;h=4b978e137cbe7c2d9f76baa6546764f6e2f7a0a6;hb=f249140854f1966d3f2333f58fa4ddd8d96001ce;hp=6fcb205e94e08ef15aacc19e8e3dc825c34037da;hpb=5e576318cdb5628381e4082c3f4a29c1e97f27a8;p=gnulib.git

diff --git a/m4/alloca.m4 b/m4/alloca.m4
index 6fcb205e9..4b978e137 100644
--- a/m4/alloca.m4
+++ b/m4/alloca.m4
@@ -1,10 +1,8 @@
-# alloca.m4 serial 4
-dnl Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
-dnl This file is free software, distributed under the terms of the GNU
-dnl General Public License.  As a special exception to the GNU General
-dnl Public License, this file may be distributed as part of a program
-dnl that contains a configuration script generated by Autoconf, under
-dnl the same distribution terms as the rest of that program.
+# alloca.m4 serial 9
+dnl Copyright (C) 2002-2004, 2006, 2007, 2009 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.
 
 AC_DEFUN([gl_FUNC_ALLOCA],
 [
@@ -19,24 +17,28 @@ AC_DEFUN([gl_FUNC_ALLOCA],
 
   # Define an additional variable used in the Makefile substitution.
   if test $ac_cv_working_alloca_h = yes; then
-    AC_EGREP_CPP([Need own alloca], [
+    AC_CACHE_CHECK([for alloca as a compiler built-in], [gl_cv_rpl_alloca], [
+      AC_EGREP_CPP([Need own alloca], [
 #if defined __GNUC__ || defined _AIX || defined _MSC_VER
-	Need own alloca
+        Need own alloca
 #endif
-      ],
-      [AC_DEFINE(HAVE_ALLOCA, 1,
-	    [Define to 1 if you have `alloca' after including <alloca.h>,
-	     a header that may be supplied by this distribution.])
-       ALLOCA_H=alloca.h],
-      [ALLOCA_H=])
+        ], [gl_cv_rpl_alloca=yes], [gl_cv_rpl_alloca=no])
+    ])
+    if test $gl_cv_rpl_alloca = yes; then
+      dnl OK, alloca can be implemented through a compiler built-in.
+      AC_DEFINE([HAVE_ALLOCA], [1],
+        [Define to 1 if you have 'alloca' after including <alloca.h>,
+         a header that may be supplied by this distribution.])
+      ALLOCA_H=alloca.h
+    else
+      dnl alloca exists as a library function, i.e. it is slow and probably
+      dnl a memory leak. Don't define HAVE_ALLOCA in this case.
+      ALLOCA_H=
+    fi
   else
     ALLOCA_H=alloca.h
   fi
   AC_SUBST([ALLOCA_H])
-
-  AC_DEFINE(HAVE_ALLOCA_H, 1,
-    [Define HAVE_ALLOCA_H for backward compatibility with older code
-     that includes <alloca.h> only if HAVE_ALLOCA_H is defined.])
 ])
 
 # Prerequisites of lib/alloca.c.