php-in-php: JIT sscanf/vfscanf — route through VmSscanf PHP not __compiler_sscanf libc LLVM (#1492)

[PurHur]

Category

php-in-php · php-src-strict

Problem

VM sscanf() / fscanf() / vfscanf() parse via ext/standard/VmSscanf.php (PHP, #3190). JIT/AOT register LLVM helpers __compiler_sscanf, __compiler_sscanf_array, __compiler_sscanf_ex, __compiler_vfscanf in lib/JIT/Builtin/Type.php with libc sscanf formatting — duplicating VM semantics and blocking self-host surface shrink.

Distinct from #4512 (by-reference array element assignment parity) and #8835 (enum format operand TypeError): this issue is JIT routing to the PHP parser.

php-src reference

• php/php-src ext/standard/sscanf.c
• VM mirror: ext/standard/VmSscanf.php, ext/standard/sscanf.php

Repro

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php -r "\$n=0; sscanf(\"42\", \"%d\", \$n); var_export(\$n); echo PHP_EOL;"
php bin/jit.php -r "\$n=0; sscanf(\"42\", \"%d\", \$n); var_export(\$n); echo PHP_EOL;"
# JIT lowers via __compiler_sscanf (libc path in Type.php)'

Scope

Layer	Path
JIT	lib/JIT/Builtin/StringSscanfJit.php (if present), lib/JIT/Builtin/Type.php
VM	ext/standard/VmSscanf.php — SSOT
No new C runtime

Done when

• JIT/AOT sscanf/vfscanf match VM + Zend on compliance / test/repro/maintainer_sscanf_*.php
• Default JIT build does not require libc sscanf LLVM for these builtins
• PR notes __compiler_sscanf* symbols removed or gated

Ref: #1492, #4512, #8835

[PurHur]

claim: PHP Runtime → PHP — batch (issues #9180, #9134)

[PurHur]

Handoff after #9180 merge in same batch: sscanf migration blocked on __compiler_sscanf ABI — out-var path needs __value__** → Variable[] marshaling in bridge before delegating to VmSscanf::parse(). __compiler_sscanf_array is the easy slice (VmSscanf::parseToArray already exists). SscanfJit.php is ~1489 lines LLVM duplicating VmSscanf.php. Next: add ext/standard/SscanfJitHelper.php + thin SscanfRuntime.php bridges (mirror #9180/#9163); retain SscanfJit for standalone AOT only.

[PurHur]

claim: PHP Runtime → PHP — batch (issues #9134, #9034)

[PurHur]

Merged #11122 — JIT embed __compiler_sscanf_array routes through SscanfJitHelper → VmSscanf::parseToArray. Verification: StringSscanfArrayRuntimeShrinkTest + sscanf_return_array_jit.phpt green. Out-var __compiler_sscanf ABI still LLVM (handoff note on issue).