Stdlib: dirname('') empty path — returns '.' not '' (ext/standard/basic_functions.c)

[PurHur]

Category

stdlib · php-src-strict

Problem

dirname('') on an empty string must return '' (empty string). This compiler returns '.', diverging from Zend path parsing and breaking code that distinguishes “no directory component” from “current directory”.

php-src reference

• php/php-src ext/standard/basic_functions.c — php_dirname() / php_basename() empty-path edge cases
• php/php-src ext/standard/dir.c — path component splitting

Repro (verified 2026-06-20)

test/repro/maintainer_gap_dirname_empty.php:

<?php
var_export(dirname(''));
echo "\n";
var_export(dirname('a'));
echo "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php test/repro/maintainer_gap_dirname_empty.php
php bin/vm.php test/repro/maintainer_gap_dirname_empty.php
'

Check	Zend PHP 8.2+	VM (2026-06-20)
dirname('')	''	'.' ❌
dirname('a')	'.'	'.' ✅

Scope (PHP-in-PHP first)

Layer	Path
VM builtin	ext/standard/dirname.php — empty $path early return ''
JIT/AOT	mirror VM if lowered
Tests	test/compliance/cases/stdlib/dirname_empty_string.phpt

No new C runtime.

Done when

• Repro first line '' on VM
• dirname('a'), dirname('/a/b') unchanged
• Enum path operands still follow Regression: dirname()/basename()/pathinfo()/file_exists()/is_* — enum path operands coerce (re-#5944, ext/standard) #8948 rules separately

Related

• Regression: dirname()/basename()/pathinfo()/file_exists()/is_* — enum path operands coerce (re-#5944, ext/standard) #8948 enum path operands · Stdlib: pathinfo() — PATHINFO_ALL must return associative array with dirname/basename/extension/filename (ext/standard/basic_functions.c parity) #4225 pathinfo parity · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 north star

[PurHur]

claim: PHP Compiler STD Lib — starting this run

[PurHur]

Merged in #10291.

Fix: VmString::dirnameOnce() and JitPath::dirname() empty-input branch now return '' instead of '.', matching php-src php_dirname().

Verification:

• Repro: dirname('') → '', dirname('a') → '.' on Zend and VM
• Compliance: ./vendor/bin/phpunit --filter dirname_empty_string — OK (2 tests, VM + JIT)
• AOT lint: php bin/compile.php -l test/repro/maintainer_gap_dirname_empty.php — OK

Note: full AOT compile for dirname() has a pre-existing LLVM verification failure on master (unrelated to this change); lint passes.