Regression: pack() nested call operand — empty string / null not packed bytes (ext/standard/pack.c, re-#11313) #11365

Category

stdlib · php-src-strict

Problem

When pack() is used as a nested call operand (return value passed directly to another callee such as strlen() or bin2hex()), the VM loses the packed byte string. Assignment to a variable works; nested use does not — same operand-pipeline class as #11313 / #11338.

php-src reference

• php/php-src ext/standard/pack.c — php_pack()
• PHP implementation: ext/standard/pack.php, ext/standard/PackEngine.php

Repro (verified 2026-06-24)

test/repro-maintainer/parity_pack_nested_call_operand.php

php test/repro-maintainer/parity_pack_nested_call_operand.php
php bin/vm.php test/repro-maintainer/parity_pack_nested_call_operand.php

PackEngine::pack() itself is correct when invoked from host PHP; failure is in VM nested-call return propagation.

Implementation hints (PHP-in-PHP)

• Fix VM temporary/return slot handling for nested builtin calls returning binary strings (NUL bytes must not truncate)
• Reuse the same operand fix pattern as Regression: hash_algos() returns NULL as in_array() haystack — nested call operand (ext/standard/array.c hash.c) #11313 (shared lowering / frame return path)
• JIT/AOT: verify nested pack() lowering when in scope

Done when (php-src-strict)

• Repro nested lines match Zend on VM
• Direct assignment path unchanged
• Invalid format still follows Regression: pack() invalid format returns empty string not false + Warning (re-#4532, ext/standard/pack.c) #10178 (warning + false)

Related

• Regression: hash_algos() returns NULL as in_array() haystack — nested call operand (ext/standard/array.c hash.c) #11313 · Regression: getdate()/localtime() nested strtotime() — callee receives current time not int result (ext/standard/basic_functions.c) #11338 · Regression: pack() invalid format returns empty string not false + Warning (re-#4532, ext/standard/pack.c) #10178 · php-in-php: pack() JIT/AOT — delete lib/AOT/runtime/phpc_pack.c, lower from ext/standard/VmPack.php #5231 · North star Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492