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# 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

])