alloca_.h suggested change

[Mark D. Baushke]

On FreeBSD 6.1, the file /usr/include/stdlib.h has the following
on lines 219 through 233 inclusive:

/*
 * The alloca() function can't be implemented in C, and on some
 * platforms it can't be implemented at all as a callable function.
 * The GNU C compiler provides a built-in alloca() which we can use;
 * in all other cases, provide a prototype, mainly to pacify various
 * incarnations of lint.  On platforms where alloca() is not in libc,
 * programs which use it will fail to link when compiled with non-GNU
 * compilers.
 */
#if __GNUC__ >= 2 || defined(__INTEL_COMPILER)
#undef  alloca  /* some GNU bits try to get cute and define this on their own */
#define alloca(sz) __builtin_alloca(sz)
#elif defined(lint)
void    *alloca(size_t);
#endif

This leads to warnings line this one being generated:

if gcc -DHAVE_CONFIG_H -I. -I../../lib -I..  -I../intl  -Ino/include  -g -O2 -MT
 mkdirat.o -MD -MP -MF ".deps/mkdirat.Tpo" -c -o mkdirat.o ../../lib/mkdirat.c;
 then mv -f ".deps/mkdirat.Tpo" ".deps/mkdirat.Po"; else rm -f ".deps/mkdirat.Tp
o"; exit 1; fi
In file included from ../../lib/openat-priv.h:22,
                 from ../../lib/mkdirat.c:37:
./alloca.h:38:1: warning: "alloca" redefined
In file included from ../../lib/mkdirat.c:26:
/usr/include/stdlib.h:230:1: warning: this is the location of the previous 
definition

The following patch helps to reduce the noise during a compilation.

        Thanks,
        -- Mark

Index: alloca_.h
===================================================================
RCS file: /sources/gnulib/gnulib/lib/alloca_.h,v
retrieving revision 1.8
diff -u -p -u -p -r1.8 alloca_.h
--- alloca_.h   14 May 2005 06:03:57 -0000      1.8
+++ alloca_.h   19 Jun 2006 08:29:51 -0000
@@ -35,7 +35,9 @@
  */
 
 #ifdef __GNUC__
-# define alloca __builtin_alloca
+# ifndef alloca
+#  define alloca __builtin_alloca
+# endif
 #elif defined _AIX
 # define alloca __alloca
 #elif defined _MSC_VER