mktime: Work around TZ problem on native Windows.

* lib/mktime.c: Add #ifs to make the algorithmic workaround independent
from the native Windows workaround.
* m4/mktime.m4 (gl_FUNC_MKTIME_WORKS): New macro, extracted from
gl_FUNC_MKTIME. If guessing, set gl_cv_func_working_mktime to
'guessing no'.
(gl_FUNC_MKTIME): Require it. Require AC_CANONICAL_HOST.
Set REPLACE_MKTIME to 1 on native Windows. Define NEED_MKTIME_WORKING,
NEED_MKTIME_WINDOWS.
(gl_FUNC_MKTIME_INTERNAL): Require gl_FUNC_MKTIME_WORKS, not
gl_FUNC_MKTIME. Set WANT_MKTIME_INTERNAL, not REPLACE_MKTIME. Define
NEED_MKTIME_INTERNAL.
* m4/timegm.m4 (gl_FUNC_TIMEGM): Require gl_FUNC_MKTIME_WORKS, not
gl_FUNC_MKTIME. Cope with 'guessing yes' value.
* modules/mktime-internal (configure.ac): Test WANT_MKTIME_INTERNAL,
not REPLACE_MKTIME.
* doc/posix-functions/mktime.texi: Mention the native Windows
workaround.

1 files changed, 40 insertions, 19 deletions

diff --git a/m4/mktime.m4 b/m4/mktime.m4
index d594ddc58b..31da65e8b2 100644
--- a/m4/mktime.m4
+++ b/m4/mktime.m4
@@ -1,4 +1,4 @@
-# serial 27
+# serial 28
 dnl Copyright (C) 2002-2003, 2005-2007, 2009-2017 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -21,9 +21,9 @@ AC_DEFUN([gl_TIME_T_IS_SIGNED],
   fi
 ])
 
-AC_DEFUN([gl_FUNC_MKTIME],
+dnl Test whether mktime works. Set gl_cv_func_working_mktime.
+AC_DEFUN([gl_FUNC_MKTIME_WORKS],
 [
-  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
   AC_REQUIRE([gl_TIME_T_IS_SIGNED])
 
   dnl We don't use AC_FUNC_MKTIME any more, because it is no longer maintained
@@ -239,29 +239,50 @@ main ()
 }]])],
        [gl_cv_func_working_mktime=yes],
        [gl_cv_func_working_mktime=no],
-       [gl_cv_func_working_mktime=no])
+       [gl_cv_func_working_mktime="guessing no"])
     ])
+])
+
+dnl Main macro of module 'mktime'.
+AC_DEFUN([gl_FUNC_MKTIME],
+[
+  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_REQUIRE([gl_FUNC_MKTIME_WORKS])
 
-  if test $gl_cv_func_working_mktime = no; then
+  REPLACE_MKTIME=0
+  if test "$gl_cv_func_working_mktime" != yes; then
     REPLACE_MKTIME=1
-  else
-    REPLACE_MKTIME=0
+    AC_DEFINE([NEED_MKTIME_WORKING], [1],
+      [Define if the compilation of mktime.c should define 'mktime'
+       with the algorithmic workarounds.])
   fi
+  case "$host_os" in
+    mingw*)
+      REPLACE_MKTIME=1
+      AC_DEFINE([NEED_MKTIME_WINDOWS], [1],
+        [Define if the compilation of mktime.c should define 'mktime'
+         with the native Windows TZ workaround.])
+      ;;
+  esac
 ])
 
+dnl Main macro of module 'mktime-internal'.
 AC_DEFUN([gl_FUNC_MKTIME_INTERNAL], [
-  AC_REQUIRE([gl_FUNC_MKTIME])
-  if test $REPLACE_MKTIME = 0; then
-    dnl BeOS has __mktime_internal in libc, but other platforms don't.
-    AC_CHECK_FUNC([__mktime_internal],
-      [AC_DEFINE([mktime_internal], [__mktime_internal],
-         [Define to the real name of the mktime_internal function.])
-      ],
-      [dnl mktime works but it doesn't export __mktime_internal,
-       dnl so we need to substitute our own mktime implementation.
-       REPLACE_MKTIME=1
-      ])
-  fi
+  AC_REQUIRE([gl_FUNC_MKTIME_WORKS])
+
+  WANT_MKTIME_INTERNAL=0
+  dnl BeOS has __mktime_internal in libc, but other platforms don't.
+  AC_CHECK_FUNC([__mktime_internal],
+    [AC_DEFINE([mktime_internal], [__mktime_internal],
+       [Define to the real name of the mktime_internal function.])
+    ],
+    [dnl mktime works but it doesn't export __mktime_internal,
+     dnl so we need to substitute our own mktime implementation.
+     WANT_MKTIME_INTERNAL=1
+     AC_DEFINE([NEED_MKTIME_INTERNAL], [1],
+       [Define if the compilation of mktime.c should define 'mktime_internal'.])
+    ])
 ])
 
 # Prerequisites of lib/mktime.c.