Still leaks, even in PHP 7. dual_it doesn't implement GC handling.

@nikic why dual_it can not be GCed like any other object and is this something than can be fixed?

https://3v4l.org/AL2Hr the issue seems to be present even if the callback is static but the (outer) Iterator is linked with any object

The bug author here.

Thank you for fixing the issue with SPL iterators. However, the original issue was about circular references on callbacks in general, and not specifically about handling circular references in SPL iterators. I see the bug title was changed on 2020-10-01, affecting its meaning quite much. Among the 6 cases provided (https://gist.github.com/5lava/53aa2e53c7f8c658f045), only one of them had to do with SPL iterators. I tested that case and I confirm it's fixed, but the 2nd one still leaks, as it did 7 years ago.

I did not re-test cases 3-6 since then, they are rather specific and I don't know if that's something that has to be addressed in the corresponding extensions or PHP core itself.

That does not, however, diminish the scale of the problem. For example, with curl:

// TEST 7: curl callback
$obj->a = curl_init('https://www.php.net/');
curl_setopt($obj->a, CURLOPT_HEADERFUNCTION, static function() use ($obj) {});

That leaks. Or with PDO/sqlite:

// TEST 8: PDO/sqlite callback
$db = new PDO('sqlite::memory:');
$db->sqliteCreateFunction('md5rev', static function() use ($obj) {}, 1);

That leaks, too. My point being: the bug (the reported one!) was NOT fixed.

@nikic I'd appreciate some input from you regarding this matter. Thank you.

This issue isn't really related to callbacks, it's a question of whether the specific object holding the callback implements GC support. As such, it needs to be addressed on a case-by-case basis. Most of the examples you listed were in 3rd-party extensions over which we have no control.

I will however check the additional two cases you just provided, those are part of our responsibility :)

Thanks, @nikic, I appreciate your attention to this problem.

In the meantime, correction my previous comment, test 8 should read as follows (replaced $db with $obj->a):

// TEST 8: PDO/sqlite callback
$obj->a = new PDO('sqlite::memory:');
$obj->a->sqliteCreateFunction('md5rev', static function() use ($obj) {}, 1);

I checked test case 7, and that one no longer leaks since PHP 8.0. GC support for  CurlHandle has been implemented as part of the migration from resources to objects (resources do not support cycle GC).

I've implemented a fix for test case 8 in https://github.com/php/php-src/pull/6262. However, this one will only go into PHP 8.1, because it changes the internal PDO ABI.

The PDO SQLite GC fix has landed, so I'm closing this again.

Very much appreciated!