X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Falloca.m4;h=eb62e0e7a52f16787cd5ac5084def332d5874aed;hb=74f8d5870e0fd68701ff379775a5f0a439bfb5b3;hp=793cf0ac0e1d72d74cd137a613aa97d8682b882f;hpb=968cc4b0e8a516793b5c095de542744b17df05fa;p=gnulib.git

diff --git a/m4/alloca.m4 b/m4/alloca.m4
index 793cf0ac0..eb62e0e7a 100644
--- a/m4/alloca.m4
+++ b/m4/alloca.m4
@@ -1,10 +1,8 @@
-# alloca.m4 serial 3
-dnl Copyright (C) 2002-2003 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 7
+dnl Copyright (C) 2002-2004, 2006 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],
 [
@@ -18,15 +16,33 @@ AC_DEFUN([gl_FUNC_ALLOCA],
   fi
 
   # Define an additional variable used in the Makefile substitution.
-
-  AC_EGREP_CPP([Need own alloca], [
-#if defined __GNUC__ || defined _MSC_VER || !HAVE_ALLOCA_H
-  Need own alloca
+  if test $ac_cv_working_alloca_h = yes; then
+    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
 #endif
-    ],
-    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.