1 files changed, 9 insertions, 13 deletions

diff --git a/gl/m4/mmap-anon.m4 b/gl/m4/mmap-anon.m4
index 61ca0120..b5e323d4 100644
--- a/gl/m4/mmap-anon.m4
+++ b/gl/m4/mmap-anon.m4
@@ -1,18 +1,17 @@
 # mmap-anon.m4
-# serial 12
-dnl Copyright (C) 2005, 2007, 2009-2024 Free Software Foundation, Inc.
+# serial 15
+dnl Copyright (C) 2005, 2007, 2009-2026 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.
+dnl This file is offered as-is, without any warranty.
 
 # 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 Linux, AIX, Solaris, Cygwin, Interix, Haiku, both MAP_ANONYMOUS and
+#   MAP_ANON exist and have the same value.
 # - On HP-UX, only MAP_ANONYMOUS exists.
 # - On Mac OS X, FreeBSD, NetBSD, OpenBSD, Minix, only MAP_ANON exists.
-# - On IRIX, neither exists, and a file descriptor opened to /dev/zero must be
-#   used.
 
 AC_DEFUN_ONCE([gl_FUNC_MMAP_ANON],
 [
@@ -22,11 +21,13 @@ AC_DEFUN_ONCE([gl_FUNC_MMAP_ANON],
   # 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])
+  # Instead, assume that mmap() exists if and only if <sys/mman.h> exists.
+  # Code needs to tests HAVE_SYS_MMAN_H, not HAVE_MMAP.
+  AC_CHECK_HEADERS_ONCE([sys/mman.h])
 
   # Try to allow MAP_ANONYMOUS.
   gl_have_mmap_anonymous=no
-  if test $gl_have_mmap = yes; then
+  if test $ac_cv_header_sys_mman_h = yes; then
     AC_MSG_CHECKING([for MAP_ANONYMOUS])
     AC_EGREP_CPP([I cannot identify this map], [
 #include <sys/mman.h>
@@ -47,10 +48,5 @@ AC_DEFUN_ONCE([gl_FUNC_MMAP_ANON],
          gl_have_mmap_anonymous=yes])
     fi
     AC_MSG_RESULT([$gl_have_mmap_anonymous])
-    if test $gl_have_mmap_anonymous = yes; then
-      AC_DEFINE([HAVE_MAP_ANONYMOUS], [1],
-        [Define to 1 if mmap()'s MAP_ANONYMOUS flag is available after including
-         config.h and <sys/mman.h>.])
-    fi
   fi
 ])