php-in-php: drop always-on LibcExtern mkstemp/memchr after JitTempnamKernel module-local (#31637 shape)

[PurHur]

Category

php-in-php · runtime-shrink (#1492, peer #31637 / #31606 / #31458)

Problem

Always-on LibcExtern still registers libc mkstemp(3) and memchr(3) even though the sole NestedJIT lookupFunction consumer (JitTempnamKernel::ensureLibc) already declares both module-locally. User-script tempnam() routes through PHP (TempnamJitHelper / StringTempnam / VmFsTempnam*) — not these always-on rows.

Symbol	Sole lookupFunction consumers	Already module-local
mkstemp	JitTempnamKernel	yes (ensureLibc)
memchr	JitTempnamKernel	yes (ensureLibc)

Path	Today	Target
User-script tempnam()	PHP helpers (already)	unchanged
LibcExtern	always-on mkstemp memchr	drop both rows
JitTempnamKernel	ensureLibc already declares	unchanged (cite this issue)
MCJIT host pin list	McjitEmbedRuntime may keep memchr for reloc	unchanged (not LibcExtern)

php-src reference

• php/php-src ext/standard/file.c — PHP_FUNCTION(tempnam) (semantics stay in PHP; libc is thin ABI inside NestedJIT leaf only)

PHP implementation target

• lib/JIT/LibcExtern.php — drop 'mkstemp' and 'memchr' rows; cite this issue
• ext/standard/JitTempnamKernel.php — cite this issue on the existing ensureLibc decls
• test/unit/LibcExternDeadDeclsRuntimeShrinkTest.php — flip keep→drop for mkstemp; add memchr to deletedDecls
• test/unit/TempnamRuntimeShrinkTest.php — assert kernel still looks up mkstemp after ensure

Repro / verify

./script/phpunit.sh --filter 'LibcExternDeadDeclsRuntimeShrinkTest|TempnamRuntimeShrinkTest|VmFsTouchTempnamRuntimeShrinkTest|StrrchrRuntimeShrinkTest'
./script/docker-exec.sh -- bash -lc 'php bin/vm.php -r '\''$p=tempnam(sys_get_temp_dir(),"phpc"); echo is_string($p)?1:0; @unlink($p);'\'''

Done when

• LibcExtern has no 'mkstemp' => or 'memchr' => row
• JitTempnamKernel::ensureLibc still declares both before lookupFunction
• User-script tempnam() still works on VM
• LibcExternDeadDeclsRuntimeShrinkTest + TempnamRuntimeShrinkTest green
• php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: PHP Runtime → PHP — starting this run (drop always-on LibcExtern mkstemp/memchr)

[PurHur]

Merged in #31657.

Verification:

• ./script/phpunit.sh --filter 'LibcExternDeadDeclsRuntimeShrinkTest|TempnamRuntimeShrinkTest|VmFsTouchTempnamRuntimeShrinkTest|StrrchrRuntimeShrinkTest' → OK (30 tests, 216 assertions)
• VM tempnam(sys_get_temp_dir(),"phpc") smoke → 1 (string path)

C / always-on shrink: dropped LibcExtern 'mkstemp' + 'memchr' rows; JitTempnamKernel::ensureLibc already module-local. lib/AOT/runtime/*.c still empty.