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regex: avoid a UBSAN failure: remove an unnecessary DEBUG_ASSERT

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* lib/regex_internal.c (re_node_set_insert): Remove the DEBUG_ASSERT
and instead return early for an attempt to insert an ELEM that is
already present in the set.  Relax the function's comment that says
there should be no duplicate.  This function is called from many
places and has been working fine.  With its nontrivial backrefs,
the sample regexp apparently elicits enough backtracking retries
and state-set merges to trigger this duplicate insertion attempt.
Reported by Bruno Haible in
https://lists.gnu.org/r/bug-gnulib/2026-04/msg00138.html
This commit is contained in:
Jim Meyering
2026-04-19 09:52:26 -07:00
parent 1a8421ada2
commit 76eb993a7b
2 changed files with 18 additions and 3 deletions
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13
ChangeLog
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@@ -1,3 +1,16 @@
2026-04-19 Jim Meyering <meyering@meta.com>
regex: avoid a UBSAN failure: remove an unnecessary DEBUG_ASSERT
* lib/regex_internal.c (re_node_set_insert): Remove the DEBUG_ASSERT
and instead return early for an attempt to insert an ELEM that is
already present in the set. Relax the function's comment that says
there should be no duplicate. This function is called from many
places and has been working fine. With its nontrivial backrefs,
the sample regexp apparently elicits enough backtracking retries
and state-set merges to trigger this duplicate insertion attempt.
Reported by Bruno Haible in
https://lists.gnu.org/r/bug-gnulib/2026-04/msg00138.html
2026-04-19 Bruno Haible <bruno@clisp.org>
regex tests: Add a test case that triggers an assertion failure.

8
lib/regex_internal.c
View File

@@ -1241,8 +1241,8 @@ re_node_set_merge (re_node_set *dest, const re_node_set *src)
}
/* Insert the new element ELEM to the re_node_set* SET.
SET should not already have ELEM.
Return true if successful. */
SET is not expected to already contain ELEM, but tolerate
duplicates as a no-op. Return true if successful. */
static bool
__attribute_warn_unused_result__
@@ -1286,7 +1286,9 @@ re_node_set_insert (re_node_set *set, Idx elem)
{
for (idx = set->nelem; set->elems[idx - 1] > elem; idx--)
set->elems[idx] = set->elems[idx - 1];
DEBUG_ASSERT (set->elems[idx - 1] < elem);
/* Already in set. Return early. */
if (__glibc_unlikely (set->elems[idx - 1] == elem))
return true;
}
/* Insert the new element. */