Segmentation Fault during OPCache Preload in PHP 8.1+

[michdingpayc]

Description

Dear PHP Maintainers,

The following code, a barebones reproduction is available at https://github.com/michdingpayc/preload-segfault-minimum-reproduction
The problematic preloaded file:

class Root1_Constant_Referencer extends Root2_Empty_Empty
// Removing the extends clause will cause preloading to succeed
// Changing the extends clause to Root1_Constant_Empty will cause preloading to succeed
// Changing the extends clause to a non-existent class will continue causing preloading to segfault
{
    protected $propertyReferencingAnExternalConstant = Root1_Constant_Definer::CONSTANT;
    // Removing this line will cause preloading to succeed
    // Changing this to a hardcoded value will cause preloading to succeed
}

preload.php:

echo "Preload started." . PHP_EOL;

$files = require __DIR__ . '/vendor/composer/autoload_classmap.php';

foreach ($files as $file) {
    @opcache_compile_file($file);
}

echo "Finished preloading" . PHP_EOL;

Resulted in this output:

$ docker-compose up
Recreating preload-segfault-minimum-reproduction_webpreloader_1 ...
Recreating preload-segfault-minimum-reproduction_webpreloader_1 ... done
Attaching to preload-segfault-minimum-reproduction_webpreloader_1
webpreloader_1  | Preload started.
webpreloader_1  | Finished preloading
preload-segfault-minimum-reproduction_webpreloader_1 exited with code 139

But I expected this output instead:
(No segmentation Fault. The following output occurs if you comment out the opcache_compile_file call in preload.php)

$ docker-compose up
Starting preload-segfault-minimum-reproduction_webpreloader_1 ...
Starting preload-segfault-minimum-reproduction_webpreloader_1 ... done
Attaching to preload-segfault-minimum-reproduction_webpreloader_1
webpreloader_1  | Preload started.
webpreloader_1  | Finished preloading
webpreloader_1  | Thu Nov 17 18:15:38 2022 (1): Message Cached script '$PRELOAD$'
webpreloader_1  | Thu Nov 17 18:15:38 2022 (1): Message Cached script '/var/www/html/lib/preload.php'
webpreloader_1  | Thu Nov 17 18:15:38 2022 (1): Message Cached script '/var/www/html/lib/vendor/composer/autoload_classmap.php'

Recommendations attempted: (in all cases the result is the same)

1. Changing base docker image from php:8.1.1-fpm-alpine3.15 to php:8.1.12-fpm-alpine3.15 and php:8.2-rc-fpm-alpine3.15.
2. Different settings for opcache.jit directive: disable, 0, 0000, 0205, 1205.
3. Setting opcache.jit_buffer_size directive to 0.

Similar to #7817 though narrower in scope.

Running the docker-compose command in the linked repository will consistently reproduce the issue. This is a blocker for our PHP 8.1 migration. Will you please assist?

PHP Version

PHP 8.1.1 8.1.12 8.2

Operating System

Docker php:8.1.1-fpm-alpine3.15

[michdingpayc]

Here is a relevant detail I believe wasn't clear in my original posting.

After a composer install, Root2_Empty_Empty is not listed in the vendor/composer/autoload_classmap.php file. This is by design. I would expect the following warning:

Can't preload unlinked class Root1_Constant_Referencer: Unknown parent Root2_Empty_Empty in /var/www/html/lib/packages/Root1/src/Constant/Referencer.php on line 3

Indeed this warning shows (with no segmentation fault) when the reference to Root1_Constant_Definer::CONSTANT is removed from the problematic file. However, instead we see a segmentation fault. Interestingly, the file containing Root1_Constant_Definer is listed in the vendor/composer/autoload_classmap.php file and should be preloaded.

It seems to be related to BOTH an unknown parent class AND an external constant reference.

[arnaud-lb]

Thank you for the high quality bug report!