Bug #78589 [NEW]: Memory leak with GC + __destruct()

From: nikic Operating system: PHP version: 7.4Git-2019-09-23 (Git) Package: Scripting Engine problem Bug Type: Bug Bug description:Memory leak with GC + __destruct() Description: ------------ This is reduced from an OSS-Fuzz testcase involving unserialize(), but turns out to be some kind of generic GC bug. It is related to the changes to __destruct() handling in 7.4. Test script: --------------- class Test { public function __destruct() {} } $test = new Test; $test->foo = [&$test->foo]; $ary = [&$ary, $test]; unset($ary, $test); gc_collect_cycles(); Actual result: -------------- [Mon Sep 23 12:17:48 2019] Script: '/home/nikic/php-src-fuzz/t009.php' Zend/zend_vm_execute.h(27609) : Freeing 0x00007f8220201940 (32 bytes), script=/home/nikic/php-src-fuzz/t009.php [Mon Sep 23 12:17:48 2019] Script: '/home/nikic/php-src-fuzz/t009.php' /home/nikic/php-src-fuzz/Zend/zend_hash.c(256) : Freeing 0x00007f82202588a0 (56 bytes), script=/home/nikic/php-src-fuzz/t009.php [Mon Sep 23 12:17:48 2019] Script: '/home/nikic/php-src-fuzz/t009.php' /home/nikic/php-src-fuzz/Zend/zend_hash.c(131) : Freeing 0x00007f822025c280 (264 bytes), script=/home/nikic/php-src-fuzz/t009.php === Total 3 memory leaks detected === -- Edit bug report at https://bugs.php.net/bug.php?id=78589&edit=1 -- Fix committed: https://bugs.php.net/fix.php?id=78589&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=78589&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=78589&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=78589&r=needscript Try newer version: https://bugs.php.net/fix.php?id=78589&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=78589&r=support Expected behavior: https://bugs.php.net/fix.php?id=78589&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=78589&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=78589&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=78589&r=globals PHP version support discontinued: https://bugs.php.net/fix.php?id=78589&r=phptooold Daylight Savings: https://bugs.php.net/fix.php?id=78589&r=dst IIS Stability: https://bugs.php.net/fix.php?id=78589&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=78589&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=78589&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=78589&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=78589&r=mysqlcfg