Add comments.

diff --git a/ChangeLog b/ChangeLog
index ba732851b8007d6bb749eb60cdeffffbe5de8b6e..ffa4100a382ed9fdd2bb806861045f8b28447e0c 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2009-05-12  Bruno Haible  <bruno@clisp.org>
+
+       * m4/mmap-anon.m4 (gl_FUNC_MMAP_ANON): Add comments.
+
 2009-05-12  Jim Meyering  <meyering@redhat.com>
 
        * top/maint.mk: Adjust backslash alignment.

diff --git a/m4/mmap-anon.m4 b/m4/mmap-anon.m4
index 025c904e4131ea8f118d1641cde75a8df6875be2..91cd95b232862850cad26daa3732ce8902ab4aab 100644 (file)
--- a/m4/mmap-anon.m4
+++ b/m4/mmap-anon.m4
@@ -1,9 +1,18 @@
-# mmap-anon.m4 serial 5
+# mmap-anon.m4 serial 6
 dnl Copyright (C) 2005, 2007, 2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
+# Detect how mmap can be used to create anonymous (not file-backed) memory
+# mappings.
+# - On Linux, AIX, OSF/1, Solaris, Cygwin, Interix, Haiku, both MAP_ANONYMOUS
+#   and MAP_ANON exist and have the same value.
+# - On HP-UX, only MAP_ANONYMOUS exists.
+# - On MacOS X, FreeBSD, NetBSD, OpenBSD, only MAP_ANON exists.
+# - On IRIX, neither exists, and a file descriptor opened to /dev/zero must be
+#   used.
+
 AC_DEFUN([gl_FUNC_MMAP_ANON],
 [
   dnl Work around a bug of AC_EGREP_CPP in autoconf-2.57.