AC_DEFUN([AX_PTRDIFF_ALIASES_INT], [
	ax_saved_CFLAGS="$CFLAGS"
	CFLAGS="$CFLAGS -Werror"

	AC_CACHE_CHECK([whether ptrdiff_t aliases int], [ax_cv_ptrdiff_aliases_int], [
		AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
			@%:@include <stddef.h>
		]], [[
			int a = 23;
			ptrdiff_t *b = &a;
		]])],
		[ax_cv_ptrdiff_aliases_int=yes],
		[ax_cv_ptrdiff_aliases_int=no])
	])
	AS_IF([test "x$ax_cv_ptrdiff_aliases_int" = "xyes"], [
		AC_DEFINE([PTRDIFF_ALIASES_INT], [1], [Whether ptrdiff_t aliases int])
	])

	CFLAGS="$ax_saved_CFLAGS"
])dnl