Try to make stack direction detection more reliable on GCC 4.7.0 and later.

  AC_RUN_IFELSE([AC_LANG_SOURCE([[

#include <stdio.h>

#if __GNUC__ >= 4

int f2(char * mark) __attribute__((noinline));

#else

int f2(char * mark);

#endif

int f1() {

  char d = 0;

  return f2(&d);

}

int f2(char * mark) {

  char c = 0;

  /* The purpose of this printf call is to prevent the compiler

     from inlining this function (like gcc 4.7.0 does).

     This is hoped to be portable, otherwise compiler specific

     pragmas or attributes would be needed. (like gcc __attribute__((noinline))

     pragmas or attributes would be needed. (like gcc __attribute__((noinline)))

   */

  printf("callee frame = %p, caller frame = %p, ", &c, mark);

  return &c - mark;

}

int f1() {

  char d = 0;

  return f2(&d);

}

int main() {

  if (f1() > 0)

    return 1;