gnulib/import/m4/mmap-anon.m4

   1 # mmap-anon.m4 serial 10
   2 dnl Copyright (C) 2005, 2007, 2009-2019 Free Software Foundation, Inc.
   3 dnl This file is free software; the Free Software Foundation
   4 dnl gives unlimited permission to copy and/or distribute it,
   5 dnl 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
  16 AC_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 ])