Static $__joinPoint keeps the first instance of every woven class alive

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  • #802 di @lisachenko — integrata

Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
22/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
php
Ambito
backend

Direzione di ricerca

Start with the generated static $__joinPoint initialiser and AbstractMethodInvocation::$closureToCall, then read DynamicTraitAliasMethodInvocation::resolveOriginalMethod(), which uses the closure only to find the method. Reproduce the leak with the WeakReference snippet from the issue. Done means the first instance is collectable after gc_collect_cycles() without changing invocation results, and composer test:performance shows no regression. A linked pull request (#802) already exists, so check it before starting.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Bug PHP-8.4 PHP-8.5 PHP-8.6

What happens

Each intercepted instance method creates its joinpoint once, in a function-scoped static:

static $__joinPoint = InterceptorInjector::forMethod(
    self::class, 'sum', [...],
    $this->sumOriginalAlias(...),   // captures $this of the first call
);

The first-class callable captures the object of the first call. It is stored in AbstractMethodInvocation::$closureToCall (protected readonly Closure) and never released, so that object can't be garbage-collected until the end of the request:

$a = new Calc(); $a->sum(1, 1); $wa = WeakReference::create($a); unset($a); gc_collect_cycles();
$b = new Calc(); $b->sum(1, 1); $wb = WeakReference::create($b); unset($b); gc_collect_cycles();
var_dump($wa->get() !== null, $wb->get() !== null); // true, false: the first instance is still alive

The cost is one object per intercepted method, plus whatever that object references: entities, request objects, large graphs. Destructors of those objects run late. This isn't specific to PHP 8.6; it was found while checking whether PFA could replace this callable. PFA can't: 8.6 has no placeholder for $this, which the PFA RFC lists as future scope.

Cause

DynamicTraitAliasMethodInvocation only uses the closure to find the method: resolveOriginalMethod() reads the scope class and name, then calls ReflectionMethod::invokeArgs() on the current instance. The captured $this is never used.

Proposed fix (options)

  1. Pass the alias name instead of a callable, for example InterceptorInjector::forMethod(self::class, 'sum', [...], 'sumOriginalAlias'), and resolve new ReflectionMethod(self::class, 'sumOriginalAlias') lazily. For inherited methods without an alias, resolve the prototype from the parent class. This needs a migration path for the forMethod() signature and for existing caches.
  2. Smaller fix: unset the closure after resolveOriginalMethod(). This needs $closureToCall to stop being readonly for dynamic invocations, and it only frees the instance after the first call reaches the original body. An around advice that never proceeds keeps it alive.

Option 1 also makes the generated code a bit smaller. Check it with composer test:performance, since this touches the hot path.

Part of #789.

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