gnats/414: Wrong dates in PRs if no %z support in strftime(3)

[Lars . Henriksen]

>Number:         414
>Category:       gnats
>Synopsis:       Wrong dates in PRs if no %z support in strftime(3)
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Sep 12 10:18:07 -0400 2002
>Originator:     Lars Henriksen
>Release:        4.0-beta1
>Organization:

>Environment:
Tru64
>Description:
On systems where strftime(3) does not support the format
code %z (numeric GMT offset), the dates in PRs are not correct if the local 
timezone is different from GMT.

The cause is a bug in gnats_strftime(). The problem is the
brokentime pointer passed to gnats_strftime(). It points to
static data that may be overwritten by calls to (among others) gmtime().

Exactly this happens in the routine minutes_gmt_offset(),
whereupon the now invalid brokentime pointer is passed on
to strftime().

Patch supplied.
>How-To-Repeat:

>Fix:
Index: misc.c
===================================================================
RCS file: /cvsroot/gnats/gnats/gnats/misc.c,v
retrieving revision 1.36
diff -u -r1.36 misc.c
--- misc.c      6 Jan 2002 16:13:20 -0000       1.36
+++ misc.c      12 Sep 2002 14:16:12 -0000
@@ -568,6 +568,11 @@
       char *fixed_template = (char*)xmalloc (strlen(template)+FORMAT_PADDING);
       const char *in = template;
       char *out = fixed_template;
+      /* Because brokentime points to static data (allocated
+       * by localtime()), it cannot be passed to a subroutine
+       * and then later be relied on to point to the same data. */
+      struct tm btime = *brokentime;
+      int result;
      
       while (*in != '\0')
        {
@@ -602,12 +607,9 @@
            }
        }
       *out = '\0';
-    
-      {
-       int result = strftime (s, size, fixed_template, brokentime);
-       free (fixed_template);
-       return result;
-      }
+      result = strftime (s, size, fixed_template, &btime);
+      free (fixed_template);
+      return result;
     }
 }
>Unformatted: