X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Fmmap-anon.m4;h=14b6270d28a150c5e99d968bdd9814f1eba2c6bf;hb=4097b52187106b6a2940d28968cfecd4e53f9b4e;hp=025c904e4131ea8f118d1641cde75a8df6875be2;hpb=42d1eda5dcce2d68deab7a642e7f29bcd7144a0d;p=gnulib.git

diff --git a/m4/mmap-anon.m4 b/m4/mmap-anon.m4
index 025c904e4..14b6270d2 100644
--- a/m4/mmap-anon.m4
+++ b/m4/mmap-anon.m4
@@ -1,9 +1,18 @@
-# mmap-anon.m4 serial 5
+# mmap-anon.m4 serial 8
 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.
@@ -11,14 +20,16 @@ AC_DEFUN([gl_FUNC_MMAP_ANON],
   AC_REQUIRE([AC_PROG_EGREP])
 
   dnl Persuade glibc <sys/mman.h> to define MAP_ANONYMOUS.
-  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
 
-  # Check for mmap()
-  AC_FUNC_MMAP
+  # Check for mmap(). Don't use AC_FUNC_MMAP, because it checks too much: it
+  # fails on HP-UX 11, because MAP_FIXED mappings do not work. But this is
+  # irrelevant for anonymous mappings.
+  AC_CHECK_FUNC([mmap], [gl_have_mmap=yes], [gl_have_mmap=no])
 
   # Try to allow MAP_ANONYMOUS.
   gl_have_mmap_anonymous=no
-  if test $ac_cv_func_mmap_fixed_mapped = yes; then
+  if test $gl_have_mmap = yes; then
     AC_MSG_CHECKING([for MAP_ANONYMOUS])
     AC_EGREP_CPP([I cant identify this map.], [
 #include <sys/mman.h>