Merge commit 'a39d4083cab589d7cd6a13e8a4b8db8875261d75'

[gnulib.git] / m4 / posixver.m4

diff --git a/m4/posixver.m4 b/m4/posixver.m4
index d0639c7..5f6e1f6 100644 (file)
--- a/m4/posixver.m4
+++ b/m4/posixver.m4
@@ -1,12 +1,43 @@
-# posixver.m4 serial 2
-dnl Copyright (C) 2002, 2003 Free Software Foundation, Inc.
-dnl This file is free software, distributed under the terms of the GNU
-dnl General Public License.  As a special exception to the GNU General
-dnl Public License, this file may be distributed as part of a program
-dnl that contains a configuration script generated by Autoconf, under
-dnl the same distribution terms as the rest of that program.
+# posixver.m4 serial 12
+dnl Copyright (C) 2002-2006, 2009-2014 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.
 
 AC_DEFUN([gl_POSIXVER],
 [
-  AC_CHECK_HEADERS_ONCE(unistd.h)
+  AC_REQUIRE([gl_DEFAULT_POSIX2_VERSION])
+])
+
+# Set the default level of POSIX conformance at configure-time.
+# Build with './configure DEFAULT_POSIX2_VERSION=199209 ...' to
+# support the older version, thus preserving portability with
+# scripts that use sort +1, tail +32, etc.
+# Note however, that this breaks tools that might run commands
+# like 'sort +some-file' that conform with the newer standard.
+AC_DEFUN([gl_DEFAULT_POSIX2_VERSION],
+[
+  AC_MSG_CHECKING([for desired default level of POSIX conformance])
+  gl_default_posix2_version=none-specified
+  if test -n "$ac_cv_env_DEFAULT_POSIX2_VERSION_set"; then
+    gl_default_posix2_version=$ac_cv_env_DEFAULT_POSIX2_VERSION_value
+    AC_DEFINE_UNQUOTED([DEFAULT_POSIX2_VERSION],
+      $gl_default_posix2_version,
+      [Define the default level of POSIX conformance. The value is of
+       the form YYYYMM, specifying the year and month the standard was
+       adopted. If not defined here, it defaults to the value of
+       _POSIX2_VERSION in <unistd.h>. Define to 199209 to default to
+       POSIX 1003.2-1992, which makes standard programs like 'head',
+       'tail', and 'sort' accept obsolete options like '+10' and
+       '-10'. Define to 200112 to default to POSIX 1003.1-2001, which
+       makes these standard programs treat leading-'+' operands as
+       file names and require modern usages like '-n 10' instead of
+       '-10'. Whether defined here or not, the default can be
+       overridden at run time via the _POSIX2_VERSION environment
+       variable.])
+  fi
+  AC_MSG_RESULT([$gl_default_posix2_version])
+  AC_ARG_VAR(
+    [DEFAULT_POSIX2_VERSION],
+    [POSIX version to default to; see 'config.hin'.])
 ])