gcc/libffi/acinclude.m4

# mmap(2) blacklisting.  Some platforms provide the mmap library routine
# but don't support all of the features we need from it.
AC_DEFUN([AC_FUNC_MMAP_BLACKLIST],
[
AC_CHECK_HEADER([sys/mman.h],
		[libffi_header_sys_mman_h=yes], [libffi_header_sys_mman_h=no])
AC_CHECK_FUNC([mmap], [libffi_func_mmap=yes], [libffi_func_mmap=no])
if test "$libffi_header_sys_mman_h" != yes \
 || test "$libffi_func_mmap" != yes; then
   ac_cv_func_mmap_file=no
   ac_cv_func_mmap_dev_zero=no
   ac_cv_func_mmap_anon=no
else
   AC_CACHE_CHECK([whether read-only mmap of a plain file works],
  ac_cv_func_mmap_file,
  [# Add a system to this blacklist if
   # mmap(0, stat_size, PROT_READ, MAP_PRIVATE, fd, 0) doesn't return a
   # memory area containing the same data that you'd get if you applied
   # read() to the same fd.  The only system known to have a problem here
   # is VMS, where text files have record structure.
   case "$host_os" in
     vms* | ultrix*)
	ac_cv_func_mmap_file=no ;;
     *)
	ac_cv_func_mmap_file=yes;;
   esac])
   AC_CACHE_CHECK([whether mmap from /dev/zero works],
  ac_cv_func_mmap_dev_zero,
  [# Add a system to this blacklist if it has mmap() but /dev/zero
   # does not exist, or if mmapping /dev/zero does not give anonymous
   # zeroed pages with both the following properties:
   # 1. If you map N consecutive pages in with one call, and then
   #    unmap any subset of those pages, the pages that were not
   #    explicitly unmapped remain accessible.
   # 2. If you map two adjacent blocks of memory and then unmap them
   #    both at once, they must both go away.
   # Systems known to be in this category are Windows (all variants),
   # VMS, and Darwin.
   case "$host_os" in
     vms* | cygwin* | pe | mingw* | darwin* | ultrix* | hpux10* | hpux11.00)
	ac_cv_func_mmap_dev_zero=no ;;
     *)
	ac_cv_func_mmap_dev_zero=yes;;
   esac])

   # Unlike /dev/zero, the MAP_ANON(YMOUS) defines can be probed for.
   AC_CACHE_CHECK([for MAP_ANON(YMOUS)], ac_cv_decl_map_anon,
    [AC_TRY_COMPILE(
[#include <sys/types.h>
#include <sys/mman.h>
#include <unistd.h>

#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS MAP_ANON
#endif
],
[int n = MAP_ANONYMOUS;],
    ac_cv_decl_map_anon=yes,
    ac_cv_decl_map_anon=no)])

   if test $ac_cv_decl_map_anon = no; then
     ac_cv_func_mmap_anon=no
   else
     AC_CACHE_CHECK([whether mmap with MAP_ANON(YMOUS) works],
     ac_cv_func_mmap_anon,
  [# Add a system to this blacklist if it has mmap() and MAP_ANON or
   # MAP_ANONYMOUS, but using mmap(..., MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
   # doesn't give anonymous zeroed pages with the same properties listed
   # above for use of /dev/zero.
   # Systems known to be in this category are Windows, VMS, and SCO Unix.
   case "$host_os" in
     vms* | cygwin* | pe | mingw* | sco* | udk* )
	ac_cv_func_mmap_anon=no ;;
     *)
	ac_cv_func_mmap_anon=yes;;
   esac])
   fi
fi

if test $ac_cv_func_mmap_file = yes; then
  AC_DEFINE(HAVE_MMAP_FILE, 1,
	    [Define if read-only mmap of a plain file works.])
fi
if test $ac_cv_func_mmap_dev_zero = yes; then
  AC_DEFINE(HAVE_MMAP_DEV_ZERO, 1,
	    [Define if mmap of /dev/zero works.])
fi
if test $ac_cv_func_mmap_anon = yes; then
  AC_DEFINE(HAVE_MMAP_ANON, 1,
	    [Define if mmap with MAP_ANON(YMOUS) works.])
fi
])