1# mmap-anon.m4 serial 10
2dnl Copyright (C) 2005, 2007, 2009-2012 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7# Detect how mmap can be used to create anonymous (not file-backed) memory
8# mappings.
9# - On Linux, AIX, OSF/1, Solaris, Cygwin, Interix, Haiku, both MAP_ANONYMOUS
10#   and MAP_ANON exist and have the same value.
11# - On HP-UX, only MAP_ANONYMOUS exists.
12# - On Mac OS X, FreeBSD, NetBSD, OpenBSD, only MAP_ANON exists.
13# - On IRIX, neither exists, and a file descriptor opened to /dev/zero must be
14#   used.
15
16AC_DEFUN([gl_FUNC_MMAP_ANON],
17[
18  dnl Persuade glibc <sys/mman.h> to define MAP_ANONYMOUS.
19  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
20
21  # Check for mmap(). Don't use AC_FUNC_MMAP, because it checks too much: it
22  # fails on HP-UX 11, because MAP_FIXED mappings do not work. But this is
23  # irrelevant for anonymous mappings.
24  AC_CHECK_FUNC([mmap], [gl_have_mmap=yes], [gl_have_mmap=no])
25
26  # Try to allow MAP_ANONYMOUS.
27  gl_have_mmap_anonymous=no
28  if test $gl_have_mmap = yes; then
29    AC_MSG_CHECKING([for MAP_ANONYMOUS])
30    AC_EGREP_CPP([I cannot identify this map], [
31#include <sys/mman.h>
32#ifdef MAP_ANONYMOUS
33    I cannot identify this map
34#endif
35],
36      [gl_have_mmap_anonymous=yes])
37    if test $gl_have_mmap_anonymous != yes; then
38      AC_EGREP_CPP([I cannot identify this map], [
39#include <sys/mman.h>
40#ifdef MAP_ANON
41    I cannot identify this map
42#endif
43],
44        [AC_DEFINE([MAP_ANONYMOUS], [MAP_ANON],
45          [Define to a substitute value for mmap()'s MAP_ANONYMOUS flag.])
46         gl_have_mmap_anonymous=yes])
47    fi
48    AC_MSG_RESULT([$gl_have_mmap_anonymous])
49    if test $gl_have_mmap_anonymous = yes; then
50      AC_DEFINE([HAVE_MAP_ANONYMOUS], [1],
51        [Define to 1 if mmap()'s MAP_ANONYMOUS flag is available after including
52         config.h and <sys/mman.h>.])
53    fi
54  fi
55])
56