php-in-php: drop always-on LibcExtern malloc/realloc/free after NestedJIT module-local (#32092 shape)

[PurHur]

Category

php-in-php · runtime-shrink (#1492, peer #32092 snprintf / #31885 memcpy / #31863 memset)

Problem

Always-on LibcExtern still registers libc malloc(3) / realloc(3) / free(3) on every JIT/AOT module even though:

1. User-script allocation is PHP (MemoryManager __mm__malloc / __mm__realloc / __mm__free) — not an always-on libc row on the user-script path.
2. NestedJIT leaves (~22 files) call lookupFunction('malloc'|'realloc'|'free') for compile-time C buffers and currently rely on the always-on rows.
3. memcpy/memset already moved to ensureMemcpyDecl / ensureMemsetDecl after always-on drops (php-in-php: drop always-on LibcExtern memcpy after NestedJIT module-local (#31863 shape) #31885 / php-in-php: drop always-on LibcExtern memset after NestedJIT module-local (#31743 shape) #31863). The allocator trio is the remaining libc heap surface in the always-on table (keep syscall / __phpc_host_* MCJIT aliases).

Path	Today	Target
User-script alloc	MemoryManager __mm__*	unchanged
LibcExtern	always-on malloc/realloc/free rows	drop rows
NestedJIT consumers	rely on always-on	LibcExtern::ensureMallocFamily() before lookup
MemoryManager\Native	comment: registered by LibcExtern	ensureMallocFamily in register()
EMBED MCJIT aliases	syscall / __phpc_host_*	unchanged (#98 / #21109 / #21124)

php-src reference

• php/php-src Zend/zend_alloc.c — Zend heap (emalloc / erealloc / efree); libc malloc is the native floor this compiler still uses for LLVM C buffers
• php/php-src Zend/zend_alloc.h

PHP implementation target

• lib/JIT/LibcExtern.php — drop 'malloc'/'realloc'/'free' always-on rows; add ensureMallocFamily() (peer ensurePosixFd php-in-php: drop always-on LibcExtern open/close/read/write after NestedJIT declares module-locally (#31764 shape) #31817 / ensureMemcpyDecl php-in-php: drop always-on LibcExtern memcpy after NestedJIT module-local (#31863 shape) #31885)
• NestedJIT consumers call LibcExtern::ensureMallocFamily() before lookupFunction('malloc'|'realloc'|'free')
• lib/JIT/Builtin/MemoryManager/Native.pre — call ensureMallocFamily from register()
• test/unit/LibcExternDeadDeclsRuntimeShrinkTest.php + shrink guard — assert rows gone + consumer wiring
• Do not add new runtime/*.c logic

Repro

./script/phpunit.sh --filter 'LibcExternDeadDeclsRuntimeShrinkTest|MallocRuntimeShrinkTest'

Done when

• LibcExtern has no always-on 'malloc' => / 'realloc' => / 'free' => rows
• All NestedJIT lookupFunction('malloc'|'realloc'|'free') sites call ensureMallocFamily() first
• MemoryManager\Native::register() declares the trio module-locally
• LibcExternDeadDeclsRuntimeShrinkTest + shrink guard green
• php-src-strict; user-script alloc behavior unchanged
• syscall / __phpc_host_php_write / __phpc_host_snprintf remain

[PurHur]

claim: php-in-php runtime-migration — starting this run (drop always-on LibcExtern malloc/realloc/free)