Description

This issue started over in docker-library/php#1545 because I initially thought this was an issue with the Debian based Docker images for PHP 8.4.0RC, but since then @yosifkit and @tianon helped with realizing that it's not related to Docker at all.

The problem

This is a minimal example of a class with a property that has a set-hook, but specifically no get-hook. When you create a lazy ghost object from this class and try to access its property, PHP should call its initialization function. And it usually does.

Test code

<?php

class Foo {
    public string $bar {
        set => $value;
    }
}

$reflector = new ReflectionClass(Foo::class);

$foo = $reflector->newLazyGhost(function ($ghost) {
    $ghost->bar = 'bar';
});

echo $foo->bar;

Expected output

bar

Actual output

However, when PHP was compiled with GCC 12.2.0 (I did not have time to test any other versions) and CFLAGS="-O2", the code throws the following fatal error instead:

Fatal error: Uncaught Error: Typed property Foo::$bar must not be accessed before initialization in /workspace/test.php:15
Stack trace:
#0 {main}
  thrown in /workspace/test.php on line 15

Some more information

GCC 12.2.0 is the current version shipped with Debian "Bookworm", hence why this bug appears in the official Docker images. However, I could reproduce it outside of Docker, on a different Linux distribution, but with the same compiler version. So GCC was the common denominator, as far as I could tell.

@yosifkit could also reproduce the issue with Debian's PHP 8.4 package from the experimental repository.

In the other thread, we suspected that this could be a compiler bug in GCC. However, I'm not well-versed enough in compilers - or the internals of PHP for that matter - to really tell. So I'm leaving this here with all the information I could gather for someone who can.

PHP Version

PHP 8.4.0RC3

Operating System

No response