Bug #78933 [NEW]: Presence of a destructor affects garbage collection

From: requinix Operating system: Any (Windows?) PHP version: 7.4.0 Package: *General Issues Bug Type: Bug Bug description:Presence of a destructor affects garbage collection Description: ------------ Discovered during bug #78930. Works in PHP 7.3. With two classes forming a cyclic reference, one of them doesn't seem to be GCed properly if the other has a destructor - even if empty. It works without the destructor. The only way I've been able to reproduce *and detect* the problem has been to use ext/pdo_sqlite to open a file, then test that the file is closed using unlink(). As far as I know, this is only possible to do on Windows since Linux is supposed to allow deleting files with open handles. But this doesn't quite feel like a PDO, SQLite, or Windows issue. I assume the GC recognizes when there is a destructor that needs to be invoked, and that affects how it cleans up. Test script: --------------- <?php class Test { public $base; public $container; public function __construct(Container $c) { $this->container = $c; $this->base = new PDO("sqlite:base.sqlite", "", ""); } } class Container { public $test; public function __construct() { $this->test = new Test($this); } // commented: no errors, file deleted // uncommented: "resource temporarily unavailable", file not deleted function __destruct() { } } new Container(); gc_collect_cycles(); unlink("base.sqlite"); -- Edit bug report at https://bugs.php.net/bug.php?id=78933&edit=1 -- Fix committed: https://bugs.php.net/fix.php?id=78933&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=78933&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=78933&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=78933&r=needscript Try newer version: https://bugs.php.net/fix.php?id=78933&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=78933&r=support Expected behavior: https://bugs.php.net/fix.php?id=78933&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=78933&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=78933&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=78933&r=globals PHP version support discontinued: https://bugs.php.net/fix.php?id=78933&r=phptooold Daylight Savings: https://bugs.php.net/fix.php?id=78933&r=dst IIS Stability: https://bugs.php.net/fix.php?id=78933&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=78933&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=78933&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=78933&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=78933&r=mysqlcfg