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fix for timezone core dumps
- To: libc-hacker@cygnus.com, drepper@cygnus.com
- Subject: fix for timezone core dumps
- From: Zack Weinberg <zack@rabi.phys.columbia.edu>
- Date: Thu, 30 Jul 1998 20:14:50 -0400
The appended patch fixes the problem I was having where tst-timezone
would dump core. The problem was stack corruption in __tzstring(),
which was way too tense for a routine that gets called a handful of
times in normal programs.
I seem to be the only person with this problem so it may be that
egcs-1.0.3 miscompiles this function (is everyone else using
snapshots?) but I think it's worth fixing anyway. In the wider world
more people are going to be using 1.0.3 than 1.1.
zw
1998-07-30 20:09 -0400 Zack Weinberg <zack@rabi.phys.columbia.edu>
* time/tzset.c (__tzstring): Get rid of excessive cleverness
which was causing stack corruption.
============================================================
Index: time/tzset.c
--- time/tzset.c 1998/07/04 10:37:23 1.56
+++ time/tzset.c 1998/07/31 00:04:59
@@ -88,66 +88,51 @@
internal_function;
static void tzset_internal __P ((int always)) internal_function;
-/* Header for a list of buffers containing time zone strings. */
-struct tzstring_head
+/* List of buffers containing time zone strings. */
+struct tzstring_l
{
- struct tzstring_head *next;
- /* The buffer itself immediately follows the header.
- The buffer contains zero or more (possibly overlapping) strings.
- The last string is followed by 2 '\0's instead of the usual 1. */
+ struct tzstring_l *next;
+ size_t len; /* strlen(data) - doesn't count terminating NUL! */
+ char data[0];
};
-/* First in a list of buffers containing time zone strings.
- All the buffers but the last are read-only. */
-static struct
-{
- struct tzstring_head head;
- char data[48];
-} tzstring_list;
-
-/* Size of the last buffer in the list, not counting its header. */
-static size_t tzstring_last_buffer_size = sizeof tzstring_list.data;
-
-/* Allocate a time zone string with given contents.
- The string will never be moved or deallocated.
- However, its contents may be shared with other such strings. */
+struct tzstring_l *tzstring_list;
+
+/* Allocate a permanent home for S. It will never be moved or deallocated,
+ but may share space with other strings.
+ Don't modify the returned string. */
char *
-__tzstring (string)
- const char *string;
+__tzstring (const char *s)
{
- struct tzstring_head *h;
- size_t needed;
char *p;
+ struct tzstring_l *t, *u, *new;
+ size_t len = strlen(s);
- /* Look through time zone string list for a duplicate of this one. */
- for (h = &tzstring_list.head; ; h = h->next)
- {
- for (p = (char *) (h + 1); p[0] | p[1]; ++p)
- if (strcmp (p, string) == 0)
+ /* Walk the list and look for a match. If this string is the same
+ as the end of an already-allocated string, it can share space. */
+ for (u = t = tzstring_list; t; u = t, t = t->next)
+ if (len <= t->len)
+ {
+ p = &t->data[t->len - len];
+ if (strcmp (s, p) == 0)
return p;
- if (! h->next)
- break;
- }
-
- /* No duplicate was found. Copy to the end of this buffer if there's room;
- otherwise, append a large-enough new buffer to the list and use it. */
- ++p;
- needed = strlen (string) + 2; /* Need 2 trailing '\0's after last string. */
-
- if ((size_t) ((char *) (h + 1) + tzstring_last_buffer_size - p) < needed)
- {
- size_t buffer_size = tzstring_last_buffer_size;
- while ((buffer_size *= 2) < needed)
- continue;
- h = malloc (sizeof *h + buffer_size);
- if (h == NULL)
- return NULL;
- h->next = NULL;
- tzstring_last_buffer_size = buffer_size;
- p = (char *) (h + 1);
- }
+ }
+
+ /* Not found; allocate a new buffer. */
+ new = malloc (sizeof (struct tzstring_l) + len + 1);
+ if (!new)
+ return NULL;
+
+ new->next = NULL;
+ new->len = len;
+ strcpy (new->data, s);
+
+ if (u)
+ u->next = new;
+ else
+ tzstring_list = new;
- return strncpy (p, string, needed);
+ return new->data;
}
static char *old_tz = NULL;