Fix: AOT link fails for EVERY binary — duplicate memset declaration

[PurHur]

master cannot produce a working native binary. Measured on 8084f14996:

aot-smoke: 0 passed, 8 failed

Every case dies identically:

/opt/llvm9/ld: loop.bin.o: in function `phpc_gc_collect_cycles_impl':
main:(.text+0x47afe): undefined reference to `memset.1'

Cause

GcCollectCyclesRuntime::ensureExternal() called module->addFunction() whenever lookupFunction() threw, without first checking getNamedFunction():

try {
    $context->lookupFunction($name);
} catch (\Throwable $e) {
    $fn = $context->module->addFunction($name, $ft);   // no getNamedFunction check
    $context->registerFunction($name, $fn);
}

LibcExtern adds memset to the module and gives it a body via implementMemsetBody(), but does not always leave it in the context's function registry — so lookupFunction() throws while the symbol already exists.

addFunction() on an existing name does not fail. LLVM silently renames the second one to memset.1, which carries no body, and the link ends with an undefined reference.

Fixed by reusing the existing declaration, matching the getNamedFunction()-first pattern LibcExtern already uses.

Verified

php-compiler:22.04-dev, script/aot-smoke.sh:

	before	after
aot-smoke	0 passed, 8 failed	8 passed, 0 failed

Two defects that looked like independent AOT bugs were this one wearing a costume — both now match Zend exactly:

probe	before	after
var_dump(7)	abort, rc=134	int(7)
(new Exception)->getMessage()	segfault	msg=[]

Not fixed here

One genuine bug survives — an inherited typed-property default is not initialized under AOT:

class A { public string $p = 'hi'; }
class B extends A {}
echo (new B)->p;
// zend: hi
// aot:  Uncaught Error: Typed property A::$p must not be accessed before initialization

Filed separately.

🤖 Generated with Claude Code

[PurHur]

Maintainer review (do not merge yet)

Verified locally in php-compiler:22.04-dev by applying this patch on current master and running script/aot-smoke.sh via ./script/docker-exec.sh.

The memset.1 undefined-reference is gone. Every smoke case still fails to link, now on the sibling symbol:

aot-smoke: 0 passed, 8 failed
undefined reference to `memcpy.1`

Same LLVM rename: lookupFunction('memcpy') throws while the module already has a memcpy body (LibcExtern / NestedJIT after #31885 dropped always-on memcpy), then addFunction('memcpy') silently creates memcpy.1 with no body.

One remaining site (not in this diff):

// lib/JIT/Builtin/StringSscanfByRef.php ensureRuntimeHelpers()
try {
    $context->lookupFunction('memcpy');
} catch (\Throwable) {
    $fn = $context->module->addFunction('memcpy', ...);  // no getNamedFunction
    $context->registerFunction('memcpy', $fn);
}

Same ensureExternal shape also exists on ObStorageLlvm, OutputRewriteVarsStorage, UrlRewriterApplyRuntime, …

Please generalize getNamedFunction()-first to memcpy (and any other libc symbol this pattern declares) and re-run script/aot-smoke.sh until 8 passed, 0 failed. I will merge when that output is pasted.

GHA Compiler gate red is a php-cfg-bare-variable-read-stmt.patch apply failure on a fresh composer install — unrelated; we do not treat GHA as the merge gate.