Regression: stream_filter_append(..., null) coerces to "" — Zend TypeError (ext/standard/streamsfuncs.c)

[PurHur]

Category

stdlib · php-src-strict

Problem

Under declare(strict_types=1), stream_filter_append($stream, null) must TypeError on string $filter_name. VM soft-coerces null→"" via VmString::coerceStringBuiltinArg, then emits unable to locate filter "" and returns false.

Repro	Zend 8.2.32 (2026-08-16)	VM (2026-08-16)
declare(strict_types=1); stream_filter_append($h, null)	TypeError: stream_filter_append(): Argument #2 ($filter_name) must be of type string, null given	Warning: unable to locate filter "" + false

Distinct from closed Reflection param-name drift (#28908) and user-filter LogicException (#14001).

php-src reference

• php/php-src ext/standard/streamsfuncs.c — PHP_FUNCTION(stream_filter_append)
• php/php-src ext/standard/basic_functions.stub.php — stream_filter_append($stream, string $filter_name, int $mode = 0, mixed $params = unknown): resource

PHP implementation target

• ext/standard/stream_filter_append.php / stream_filter_prepend.php (same coerce path) — use strict string guard under strict_types (InternalStrictArg / JitStringBuiltinArg peer of trim-family); JitStreamFilter / kernel helpers; no new runtime/*.c

Repro

./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_gap_stream_filter_append_null_name.php'
# expect TypeError (match host `php test/repro/maintainer_gap_stream_filter_append_null_name.php`)

<?php
declare(strict_types=1);
$h = fopen('php://memory', 'r+');
stream_filter_append($h, null);

Done when

• Under strict_types, null $filter_name → TypeError: … Argument #2 ($filter_name) must be of type string, null given (VM + JIT/AOT when in scope)
• No soft-coerce to "" / unable to locate filter "" for this case
• Same behavior for stream_filter_prepend if it shares the coerce helper
• Compliance or unit guard; php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: PHP Compiler STD Lib — starting this run

[PurHur]

Merged in #31438.

Verification

• VM: php bin/vm.php test/repro/maintainer_gap_stream_filter_append_null_name.php → TypeError for append + prepend citing $filter_name
• ./script/phpunit.sh --filter Issue31408StreamFilterNullNameStrictTest — OK
• ./script/phpunit.sh --filter Issue31408StreamFilterNullNameStrictAotTest — OK (3× AOT run)
• Non-strict null still soft-coerces to "" / returns false