Use Gnulib's `strftime' to address bug #24130.

* libguile/stime.c (scm_strftime): Use `nstrftime ()' from Gnulib.
  This provides the same semantics on all platforms, thereby fixing
  bug #24130.

* doc/ref/posix.texi (Time): Remove note about non-portable `%Z'
  behavior.  Describe the new, portable behavior.

* test-suite/tests/time.test ("strftime")["strftime %Z doesn't return
  garbage"]: Reinstate.
  ["C99 %z format"](have-strftime-%z): Remove.
  ("GMT", "EST+5"): Don't use `have-strftime-%z'.

doc/ref/posix.texi

@@ -1,6 +1,6 @@
 @c -*-texinfo-*-
 @c This is part of the GNU Guile Reference Manual.
-@c Copyright (C)  1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2007
+@c Copyright (C)  1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008
 @c   Free Software Foundation, Inc.
 @c See the file guile.texi for copying conditions.
 
@@ -1264,27 +1264,8 @@ formatting.
 If @code{setlocale} has been called (@pxref{Locales}), month and day
 names are from the current locale and in the locale character set.
 
-Note that @samp{%Z} might print the @code{tm:zone} in @var{tm} or it
+Note that @samp{%Z} always ignores the @code{tm:zone} in @var{tm};
-might print just the current zone (@code{tzset} above).  A GNU system
+instead it prints just the current zone (@code{tzset} above).
-prints @code{tm:zone}, a strict C99 system like NetBSD prints the
-current zone.  Perhaps in the future Guile will try to get
-@code{tm:zone} used always.
-@c
-@c  The issue in the above is not just whether tm_zone exists in
-@c  struct tm, but whether libc feels it should read it.  Being a
-@c  non-C99 field, a strict C99 program won't know to set it, quite
-@c  likely leaving garbage there.  NetBSD, which has the field,
-@c  therefore takes the view that it mustn't read it.  See the PR
-@c  about this at
-@c
-@c      http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=21722
-@c
-@c  Uniformly making tm:zone used on all systems (all those which have
-@c  %Z at all of course) might be nice (either mung TZ and tzset, or
-@c  mung tzname[]).  On the other hand it would make us do more than
-@c  C99 says, and we really don't want to get intimate with the gory
-@c  details of libc time funcs, no more than can be helped.
-@c
 @end deffn
 
 @deffn {Scheme Procedure} strptime format string

libguile/stime.c

@@ -44,6 +44,7 @@
 
 #include <stdio.h>
 #include <errno.h>
+#include <strftime.h>
 
 #include "libguile/_scm.h"
 #include "libguile/async.h"
@@ -689,10 +690,9 @@ SCM_DEFINE (scm_strftime, "strftime", 2, 0, 0,
     tzset ();
 #endif
 
-    /* POSIX says strftime returns 0 on buffer overrun, but old
+    /* Use `nstrftime ()' from Gnulib, which supports all GNU extensions
-       systems (i.e. libc 4 on GNU/Linux) might return `size' in that
+       supported by glibc.  */
-       case. */
+    while ((len = nstrftime (tbuf, size, myfmt, &t, 0, 0)) == 0)
-    while ((len = strftime (tbuf, size, myfmt, &t)) == 0 || len == size)
       {
 	free (tbuf);
 	size *= 2;

test-suite/tests/time.test

@@ -1,7 +1,7 @@
 ;;;; time.test --- test suite for Guile's time functions     -*- scheme -*-
 ;;;; Jim Blandy <jimb@red-bean.com> --- June 1999, 2004
 ;;;;
-;;;; 	Copyright (C) 1999, 2004, 2006, 2007 Free Software Foundation, Inc.
+;;;; 	Copyright (C) 1999, 2004, 2006, 2007, 2008 Free Software Foundation, Inc.
 ;;;; 
 ;;;; This program is free software; you can redistribute it and/or modify
 ;;;; it under the terms of the GNU General Public License as published by
@@ -196,44 +196,19 @@
 
 (with-test-prefix "strftime"
 
-  ;; Note we must force isdst to get the ZOW zone name out of %Z on HP-UX.
+  (pass-if "strftime %Z doesn't return garbage"
-  ;; If localtime is in daylight savings then it will decide there's no
+    (let ((t (localtime (current-time))))
-  ;; daylight savings zone name for the fake ZOW, and come back empty.
+      (set-tm:zone t "ZOW")
-  ;;
+      (set-tm:isdst t 0)
-  ;; This test is disabled because on NetBSD %Z doesn't look at the tm_zone
+      (string=? (strftime "%Z" t)
-  ;; field in struct tm passed by guile.  That behaviour is reasonable
+                "ZOW")))
-  ;; enough since that field is not in C99 so a C99 program won't know it
-  ;; has to be set.  For the details on that see
-  ;;
-  ;;     http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=21722
-  ;;
-  ;; Not sure what to do about this in guile, it'd be nice for %Z to look at
-  ;; tm:zone everywhere.
-  ;;
-  ;;
-  ;; (pass-if "strftime %Z doesn't return garbage"
-  ;; 	 (let ((t (localtime (current-time))))
-  ;; 	   (set-tm:zone t "ZOW")
-  ;; 	   (set-tm:isdst t 0)
-  ;; 	   (string=? (strftime "%Z" t)
-  ;; 		     "ZOW")))
 
   (with-test-prefix "C99 %z format"
 
-    ;; C99 spec is empty string if no zone determinable
-    ;;
-    ;; on pre-C99 systems not sure what to expect if %z unsupported, probably
-    ;; "%z" unchanged in C99 if timezone
-    ;;
-    (define have-strftime-%z
-      (not (member (strftime "%z" (gmtime 0))
-		   '("" "%z"))))
-
     ;; %z here is quite possibly affected by the same tm:gmtoff vs current
     ;; zone as %Z above is, so in the following tests we make them the same.
 
     (pass-if "GMT"
-      (or have-strftime-%z (throw 'unsupported))
       (putenv "TZ=GMT+0")
       (tzset)
       (let ((tm (localtime 86400)))
@@ -243,7 +218,6 @@
     ;; because we didn't adjust for tm:gmtoff being west of Greenwich versus
     ;; tm_gmtoff being east of Greenwich
     (pass-if "EST+5"
-      (or have-strftime-%z (throw 'unsupported))
       (putenv "TZ=EST+5")
       (tzset)
       (let ((tm (localtime 86400)))