Language: ++/-- on property hooks must use get/set hooks (zend_property_hooks.c, pairs #6427)

[PurHur]

Category

language

Problem

#6427 tracks compound assignment (+=, .=, …) on property hooks. Zend also routes pre/post increment and decrement (++$obj->prop, $obj->prop++, --) through get/set hooks: read current value via get hook, compute, write via set hook.

This compiler lowers TYPE_PRE_INC / TYPE_POST_INC / dec opcodes in lib/VM.php but does not dispatch property hooks on inc/dec lvalues — hooked properties mutate backing storage or skip hooks.

php-src reference

• php/php-src Zend/zend_property_hooks.c — inc/dec on hooked properties
• php/php-src Zend/zend_execute.c — ZEND_PRE_INC_OBJ, ZEND_POST_INC_OBJ, etc.
• php/php-src Zend/zend_compile.c — inc/dec on PROP_HOOK lvalues

Repro (failure today)

<?php
class Counter {
    private int $n = 0;
    public int $count {
        get => $this->n;
        set => $this->n = $value;
    }
}
$c = new Counter();
echo $c->count, "\n";   // 0
$pre = ++$c->count;
echo "$pre {$c->count}\n"; // 1 1
$post = $c->count++;
echo "$post {$c->count}\n"; // 1 2

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php repro_property_hook_incdec.php
php bin/vm.php repro_property_hook_incdec.php'

Step	Zend	bin/vm.php today
++$c->count	get→add→set; returns new value	likely wrong count / no set hook
$c->count++	returns old value; set hook runs	likely wrong

String increment ($s++ on hooked string) and -- must follow same get/set pattern per php-src.

Scope (this repo)

Area	Files
VM	lib/VM.php — TYPE_PRE_INC, TYPE_POST_INC, TYPE_PRE_DEC, TYPE_POST_DEC paths; reuse enforceVirtualPropertyHookWrite / get-hook read
Compiler	lib/Compiler.php — compileIncDecExpr if lvalue metadata needed
JIT/AOT	lib/JIT/PropertyHookDispatch.php, lib/JIT.php — mirror VM
Tests	test/compliance/cases/language/property_hook_incdec.phpt

PHP-in-PHP first: hook dispatch stays in PHP VM/JIT lowering.

Done when

• Repro int inc/dec matches Zend on VM
• String $s++ on hooked string property matches Zend (str_increment semantics via hooks)
• Get-only hook: inc/dec assignment throws Error (same as plain assign, Language: property hooks without set — assignment must throw Error (zend_property_hooks.c) #4821)
• JIT + AOT compliance green when issue requires full pipeline
• ./script/ci-fast.sh --filter property_hook_incdec green

php-src-strict

Default — inc/dec must not write backing storage directly when hooks are defined.

Related

• Language: compound assignment (+=, .=, …) on property hooks must use get/set hooks (zend_property_hooks.c) #6427 compound assignment on hooks
• Language: property hooks without set — assignment must throw Error (zend_property_hooks.c) #4821 get-only hook assign Error
• Language: foreach by-reference on property hooks must invoke set hook (zend_property_hooks.c) #6435 foreach by-ref on hooks
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: agent-worker-lane-c — starting this run

[PurHur]

Merged #6482.

VM get/set hook dispatch for ++/-- was already implemented in #6309/#6319 (lib/VM.php, lib/JIT.php). This PR adds the remaining acceptance coverage:

• property_hook_string_incdec.phpt — string $s++ / ++$s on hooked properties
• PropertyHookIncDecJitCompileTest — LLVM compile probe (@group llvm)

Verification:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter "property_hook.*inc" test/compliance/VMTest.php'

→ OK (5 tests, 5 assertions)