Bug #69371 [NEW]: Hash table collision leads to inaccessible array keys

From: berdir Operating system: Linux PHP version: master-Git-2015-04-03 (Git) Package: Arrays related Bug Type: Bug Bug description:Hash table collision leads to inaccessible array keys Description: ------------ We're working on making Drupal 8 compatible with PHP7. A few of our tests are failing with very strange array related errors. A lot of test that have a common base class and call the same method are failing with the same problem. See https://www.drupal.org/node/2454439#comment-9788325. Basically, there are two arrays, both are keyed with the same keys. We loop over one of them and access the element in the second array. That results in a undefined index notice. But when comparing with array_keys() or var_dump(), then the array key exists. Changing the code to instead do a foreach and look for the matching key works fine: - $migration = $migrations[$migration_id]; + foreach ($migrations as $id => $migration) { + // WTF PHP7, you drunk? + if ($id === $migration_id) { + break; + } + } @ircmaxell has been debugging this and tracked it down to a hash collision between the array entries d6_user and d6_node_type, which then results in d6_node_type not being accessible. For other tests, it's other keys. This only happens in this specific scenario, we haven't been able to reproduce it in a standalone script. To run the test, get the latest Drupal 8 (branch 8.0.x), and run the test like this: php7 core/scripts/run-tests.sh --sqlite /tmp/test.sqlite --dburl sqlite://tmp/db.sqlite --class "Drupal\migrate_drupal\Tests\d6\MigrateCckFieldRevisionTest" Notes: that needs the curl and gd extensions, and it starts a second script to actually run the test. To debug with gdb for example, you need something like this: gdb --args '/usr/local/bin/php7' './core/scripts/run-tests.sh' --url '' --sqlite '/tmp/test.sqlite' --dburl 'sqlite://tmp/db.sqlite' --php '/usr/local/bin/php7' --test-id 1 --execute-test 'Drupal\migrate_drupal\Tests\d6\MigrateCckFieldRevisionTest' (the first command needs to be run first, to set up the env, look for proc_open and print the command to get he right now) -- Edit bug report at https://bugs.php.net/bug.php?id=69371&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=69371&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=69371&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=69371&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=69371&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=69371&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=69371&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=69371&r=needscript Try newer version: https://bugs.php.net/fix.php?id=69371&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=69371&r=support Expected behavior: https://bugs.php.net/fix.php?id=69371&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=69371&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=69371&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=69371&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=69371&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=69371&r=dst IIS Stability: https://bugs.php.net/fix.php?id=69371&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=69371&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=69371&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=69371&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=69371&r=mysqlcfg