2021-02-05 Paul Eggert <eggert@cs.ucla.edu>
+ regex: avoid undefined behavior
+ * lib/regexec.c (pop_fail_stack): If the stack is empty, return -1
+ instead of indulging in undefined behavior. This simplifies
+ callers, and avoids undefined behavior in some cases (see glibc
+ bug 11053, though this change does not fix that overall bug).
+
regex: improve comments
* lib/regexec.c: Add and correct comments about return values.
pop_fail_stack (struct re_fail_stack_t *fs, Idx *pidx, Idx nregs,
regmatch_t *regs, re_node_set *eps_via_nodes)
{
+ if (fs == NULL || fs->num == 0)
+ return -1;
Idx num = --fs->num;
- DEBUG_ASSERT (num >= 0);
*pidx = fs->stack[num].idx;
memcpy (regs, fs->stack[num].regs, sizeof (regmatch_t) * nregs);
re_node_set_free (eps_via_nodes);
re_free (fs->stack[num].regs);
*eps_via_nodes = fs->stack[num].eps_via_nodes;
+ DEBUG_ASSERT (0 <= fs->stack[num].node);
return fs->stack[num].node;
}
if (idx == pmatch[0].rm_eo && cur_node == mctx->last_node)
{
Idx reg_idx;
+ cur_node = -1;
if (fs)
{
for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
if (pmatch[reg_idx].rm_so > -1 && pmatch[reg_idx].rm_eo == -1)
- break;
- if (reg_idx == nmatch)
- {
- re_node_set_free (&eps_via_nodes);
- regmatch_list_free (&prev_match);
- return free_fail_stack_return (fs);
- }
- cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
- &eps_via_nodes);
+ {
+ cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
+ &eps_via_nodes);
+ break;
+ }
}
- else
+ if (cur_node < 0)
{
re_node_set_free (&eps_via_nodes);
regmatch_list_free (&prev_match);
- return REG_NOERROR;
+ return free_fail_stack_return (fs);
}
}
free_fail_stack_return (fs);
return REG_ESPACE;
}
- if (fs)
- cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
- &eps_via_nodes);
- else
+ cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch, &eps_via_nodes);
+ if (cur_node < 0)
{
re_node_set_free (&eps_via_nodes);
regmatch_list_free (&prev_match);
+ free_fail_stack_return (fs);
return REG_NOMATCH;
}
}