php-in-php: drop always-on LibcExtern strlen after NestedJIT module-local (#31997 shape)

[PurHur]

Category

php-in-php · runtime-shrink (#1492, peer #31997 strtod / #31988 strtol / #31971 strcmp)

Problem

Always-on LibcExtern still registers libc strlen(3) even though:

1. User-script strlen() already lives in PHP (ext/types/strlen.php + JitStrlen / VmString::byteLength) — not libc on char*.
2. ~65 NestedJIT leaves call lookupFunction('strlen') for compile-time C-string length (session/stream/ob/parse_str/CLI/Reflection/env) — they rely on the always-on row.
3. ext/standard/Module.php jitInit still always-declares strlen as a fallback — that path should drop with the LibcExtern row (peer php-in-php: drop always-on LibcExtern strtod after NestedJIT module-local (#31988 shape) #31997 strtod).

Path	Today	Target
User-script strlen()	ext/types PHP (JitStrlen)	unchanged
LibcExtern	always-on strlen row	drop row
NestedJIT consumers	rely on always-on	LibcExtern::ensureStrlenDecl() before lookup
Module::jitInit	always-on strlen fallback	drop; comment peer #31997
EMBED MCJIT	implementStrlenBody after always-on decl	ensureStrlenDecl then body (#98 / #21109)

php-src reference

• Userland: php/php-src ext/standard/string.c — PHP_FUNCTION(strlen)
• php/php-src Zend/zend_operators.c — Z_STRLEN / string length on zend_string, not libc strlen on user values

PHP implementation target

• lib/JIT/LibcExtern.php — drop 'strlen' always-on row; add ensureStrlenDecl(); implementStrlenBody calls it first
• NestedJIT consumers call LibcExtern::ensureStrlenDecl() before lookupFunction('strlen')
• ext/standard/Module.php — drop always-on strlen jitInit fallback
• test/unit/LibcExternDeadDeclsRuntimeShrinkTest.php + StrlenRuntimeShrinkTest — assert row gone + consumer wiring

Repro

./script/phpunit.sh --filter LibcExternDeadDeclsRuntimeShrinkTest
./script/phpunit.sh --filter StrlenRuntimeShrinkTest

Done when

• LibcExtern has no always-on 'strlen' => row
• All NestedJIT lookupFunction('strlen') sites call ensureStrlenDecl() first (or declare module-locally)
• LibcExternDeadDeclsRuntimeShrinkTest + shrink guard green
• php-src-strict; user-script strlen() behavior unchanged

[PurHur]

claim: PHP Runtime → PHP — starting this run

Drop always-on LibcExtern strlen(3); NestedJIT consumers will call ensureStrlenDecl() before lookup. User-script strlen() stays on ext/types JitStrlen / VmString.

[PurHur]

Merged in #32072.

Dropped always-on LibcExtern strlen(3) row. NestedJIT leaves call ensureStrlenDecl(); user-script strlen() stays on ext/types JitStrlen / VmString. Module::jitInit strlen fallback removed.

Verification:

• ./script/phpunit.sh --filter 'LibcExternDeadDeclsRuntimeShrinkTest|StrlenRuntimeShrinkTest|LibcExternMathRuntimeShrinkTest' → OK 33 tests, 583 assertions
• ./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/nested_trim_strlen.php' → 5

C symbols deleted: always-on 'strlen' => in lib/JIT/LibcExtern.php (no runtime/*.c added).