php-in-php: drop always-on LibcExtern strncasecmp after Object_ Type routes via __compiler_strncasecmp (#31655 shape)

[PurHur]

Category

php-in-php · runtime-shrink (#1492, peer #31655 / #31519 / #15225)

Problem

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

1. User-script strncasecmp() already routes through PHP (CaseCompareJitHelper / __compiler_strncasecmp — php-in-php: strcasecmp()/strncasecmp() JIT via CaseCompareJitHelper PHP — drop libc LLVM (#1492) #15225 / php-in-php: StringCaseCompare NestedJIT → JitVmHelperLink::ensureCompiled (#1492) #23862 / Regression: AOT password_hash(PASSWORD_BCRYPT) segfaults after build — VM/JIT match Zend (re-#26773, ext/standard/password.c) #26861).
2. The sole NestedJIT lookupFunction('strncasecmp') consumer is lib/JIT/Builtin/Type/Object_::classIdFromRuntimeName, which already calls StringCaseCompare::ensureStrncasecmpLinked but then looks up libc strncasecmp (always-on) instead of the linked __compiler_strncasecmp ABI.

Symbol	Sole lookupFunction consumer	Target
strncasecmp	Type/Object_::classIdFromRuntimeName	call __compiler_strncasecmp (already ensured)

Path	Today	Target
User-script strncasecmp()	CaseCompareJitHelper / __compiler_*	unchanged
LibcExtern	always-on strncasecmp	drop row
Object_::classIdFromRuntimeName	ensure CaseCompare + lookup libc strncasecmp	ensure + lookup __compiler_strncasecmp

php-src reference

• php/php-src ext/standard/string.c — PHP_FUNCTION(strncasecmp) (semantics stay in PHP VmString / CaseCompareJitHelper)

PHP implementation target

• lib/JIT/Builtin/Type/Object_.php — lookup StringCaseCompare::ABI_STRNCASECMP
• lib/JIT/LibcExtern.php — drop always-on 'strncasecmp' row
• test/unit/LibcExternDeadDeclsRuntimeShrinkTest.php + StrcasecmpRuntimeShrinkTest.php guards

Done when

• LibcExtern has no 'strncasecmp' => row
• Object_.php looks up __compiler_strncasecmp (not libc strncasecmp)
• User-script strncasecmp() still matches Zend via VM/JIT
• No new lib/AOT/runtime/*.c
• php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: PHP Runtime → PHP — starting this run (drop always-on LibcExtern strncasecmp; Object_ → __compiler_strncasecmp)

[PurHur]

Merged via #31685

Verification

• ./script/phpunit.sh --filter 'LibcExternDeadDeclsRuntimeShrinkTest|LibcNameCollisionRuntimeShrinkTest|StrcasecmpRuntimeShrinkTest::testObjectTypeRoutesStrncasecmpThroughCaseCompare|StrcasecmpRuntimeShrinkTest::testStrncasecmp' → OK (20 tests, 181 assertions)
• VM/JIT: strncasecmp("Ab","ab",1) → int(0); filter_var("TRUE", FILTER_VALIDATE_BOOLEAN) → bool(true)

Shrink: dropped always-on LibcExtern 'strncasecmp' row; Object_ + JitFilter use __compiler_strncasecmp. lib/AOT/runtime/*.c still empty.