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

[PurHur]

Category

stdlib · php-src-strict

Problem

realpath('') with an empty string path must resolve to the current working directory (same as realpath('.')). This compiler returns false, breaking path normalization in self-host and app code that passes user input through realpath() without an explicit . fallback.

php-src reference

• php/php-src ext/standard/basic_functions.c — php_realpath() empty-path → VCWD_GETCWD then canonicalize
• php/php-src main/php_streams.c — virtual cwd resolution

Repro (verified 2026-06-20)

test/repro/maintainer_gap_realpath_empty.php:

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

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

Runtime	Result
Zend PHP 8.2+	'/path/to/cwd' (non-empty string)
php bin/vm.php	false ❌

Scope (PHP-in-PHP first)

Layer	Path
VM builtin	ext/standard/realpath.php — treat '' like '.' before stat/canonicalize
JIT/AOT	mirror VM if realpath is lowered inline
Tests	test/compliance/cases/stdlib/realpath_empty_string.phpt

No new C runtime.

Done when

• Repro prints cwd string on VM (matches Zend in same directory)
• realpath('.') unchanged
• Invalid/nonexistent paths still false per Zend
• Targeted compliance guard green

Related

• Regression: dirname()/basename()/pathinfo()/file_exists()/is_* — enum path operands coerce (re-#5944, ext/standard) #8948 enum path operands · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 north star

[PurHur]

claim: PHP Runtime → PHP — batch (issues #10257, #10111)

[PurHur]

Merged via #10939.

Verification:

php bin/vm.php test/repro/maintainer_gap_realpath_empty.php
# prints cwd string (not false)

php bin/vm.php test/compliance/cases/stdlib/realpath_empty_string.phpt
# ok