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Regression: preg_*() /u on invalid UTF-8 — match succeeds, preg_last_error() stale (ext/pcre/php_pcre.c) #17503
Description
Category
Regression · php-src-strict
Problem
PCRE functions with the u (UTF-8) modifier must reject malformed subject strings: return false (or false from split) and set preg_last_error() to PREG_BAD_UTF8_ERROR (4). This compiler accepts invalid bytes and leaves preg_last_error() at 0.
| Repro | Zend 8.2+ | VM (2026-07-09) |
|---|---|---|
preg_match('//u', "\xFF") |
false; error 4 |
1; error 0 |
preg_split('//u', "\xFF") |
false; error 4 |
array(...); error 0 |
preg_replace('//u', 'x', "\xFF") |
false; error 4 |
mutates subject; error 0 |
php-src reference
- php/php-src
ext/pcre/php_pcre.c—php_pcre_match_impl(), UTF-8 validation /PREG_BAD_UTF8_ERROR
PHP implementation target
ext/standard/preg builtins + VM/JIT lowering — validate subject UTF-8 when pattern carriesu; propagatepreg_last_error()/preg_last_error_msg()like Zend- Prefer PHP implementation; keep any C as thin PCRE ABI only
Repro
./script/docker-exec.sh -- bash -lc '
php bin/vm.php test/repro/maintainer_gap_preg_match_invalid_utf8.php
php bin/vm.php test/repro/maintainer_gap_preg_split_invalid_utf8.php
'
# Zend: ok · VM: fail on bothDone when
-
preg_match,preg_match_all,preg_split,preg_replace,preg_grepwith/usetPREG_BAD_UTF8_ERRORon invalid UTF-8 subjects (VM + JIT/AOT where pattern is known at compile time) - Compliance
.phptguards undertest/compliance/cases/pcre/ - php-src-strict; no php-compiler-strict shortcut
Activity
PurHur commentedon Jul 9, 2026
claim: cursor-agent-lane-b — starting this run
PurHur commentedon Jul 9, 2026
Merged via #17512.
Fix:
VmPregPure::ensureUtf8SubjectForOpts()validates subject UTF-8 when pattern has/u(PCRE2_UTF), setsPREG_BAD_UTF8_ERROR(4) like Zendext/pcre/php_pcre.c.Verification (Docker):
php bin/vm.php test/repro/maintainer_gap_preg_match_invalid_utf8.php→false/ error 4php bin/vm.php test/repro/maintainer_gap_preg_split_invalid_utf8.php→false/ error 4php bin/vm.php test/compliance/cases/pcre/preg_utf8_invalid_subject.phpt— greenvendor/bin/phpunit --filter VmPregUtf8SubjectTest— 4/4 OKStdlib: reject invalid UTF-8 subjects for preg_* /u modifier (#17503) (…
chore: drop 24 more stale maintainer_gap repros (wave30 batch 2, #16660…