doc: work around mingw-w64 alloca problem with example

* doc/autoconf.texi (Particular Functions): In example code for
alloca, do not re-#define alloca.  This works around a mingw-w64
problem reported by Vincent Torri in
<http://lists.gnu.org/archive/html/autoconf/2012-01/msg00018.html>.

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 247a46ca511d245f4e733c1bb9da919119e78413..82837a2ba4e7b287520eb8d3ab23aa5d382fce18 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -4863,15 +4863,15 @@ like the following, to declare it properly.
 #endif
 #ifdef HAVE_ALLOCA_H
 # include <alloca.h>
-#elif defined __GNUC__
-# define alloca __builtin_alloca
-#elif defined _AIX
-# define alloca __alloca
-#elif defined _MSC_VER
-# include <malloc.h>
-# define alloca _alloca
-#else
-# ifndef HAVE_ALLOCA
+#elif !defined alloca
+# ifdef __GNUC__
+#  define alloca __builtin_alloca
+# elif defined _AIX
+#  define alloca __alloca
+# elif defined _MSC_VER
+#  include <malloc.h>
+#  define alloca _alloca
+# elif !defined HAVE_ALLOCA
 #  ifdef  __cplusplus
 extern "C"
 #  endif