Stdlib: mb_strlen() — encoding argument + error behavior parity with php-src ext/mbstring

[PurHur]

Category

stdlib

Problem

mb_strlen() exists but has compiler-specific constraints (UTF-8/ASCII/8BIT-only in JIT path; other encodings depend on host mbstring, and error handling differs). For parity and portability we need php-src-consistent behavior for:

• accepted values for $encoding (string, null, omitted)
• invalid encoding handling (warnings / ValueError depending on PHP version)
• interaction with internal encoding (when $encoding omitted)
• return value for empty string and multibyte characters

php-src reference

• ext/mbstring/mbstring.c — PHP_FUNCTION(mb_strlen)
• ext/mbstring/php_mbstring.h — encoding tables and option parsing
• PHPTs: ext/mbstring/tests/mb_strlen*.phpt

Repro (today)

<?php
echo mb_strlen('é', 'UTF-8'), "\n";

// Zend accepts null to mean "use internal encoding".
try {
    var_dump(mb_strlen('hello', null));
} catch (Throwable $e) {
    echo get_class($e), ": ", $e->getMessage(), "\n";
}

// Invalid encoding should match Zend (warning/ValueError + return false).
try {
    var_dump(mb_strlen('hello', 'NO_SUCH_ENCODING'));
} catch (Throwable $e) {
    echo get_class($e), ": ", $e->getMessage(), "\n";
}

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php repro.php'
php repro.php   # Zend reference (with ext/mbstring)

Scope (this repo)

• ext/types/mb_strlen.php + ext/types/JitMbStrlen.php + native helpers under lib/AOT/runtime/
• Decide parity policy for environments without host mbstring (Docker image vs harness host)
• Add/port compliance PHPTs for encoding parsing + error behavior

Done when

• $encoding accepts null/omitted like Zend and follows internal encoding rules
• Invalid encoding behavior matches php-src (exception vs warning + false) for targeted PHP version
• JIT/AOT/VM behavior aligned for UTF-8 and ASCII; documented/guarded behavior for other encodings

[PurHur]

claim: PHP Compiler Ext — I/O & Crypto — starting this run

[PurHur]

Merged in #17988.

Fix: mb_strlen() uses MbstringState::internalEncoding() when $encoding is omitted or null; invalid names raise ValueError via MbstringEncodingRegistry::assertValid(). Shared helpers: VmMbstring::resolveValidatedEncodingArg() + VmMbstring::strlen().

Verification (VM):
```bash
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro/maintainer_gap_mb_strlen_encoding.php
./vendor/bin/phpunit test/compliance/MbStrlenVMTest.php
./vendor/bin/phpunit test/compliance/MbStrlenJITTest.php
'
```
→ repro prints `1`, `int(5)`, ValueError for `NO_SUCH_ENCODING`; MbStrlen VM (3) + JIT (2) tests green.