Understand this has been merged/closed. Not seen any reports of this as of yet, however, I am getting this repeated OutOfMemoryError message.

Symfony\Component\ErrorHandler\Error\OutOfMemoryError:
Error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 81920 bytes)

  at /application/vendor/symfony/dependency-injection/Compiler/DefinitionErrorExceptionPass.php:69 

Same here. The other day I had an errored service definition and I also got the OutOfMemoryError. Calling bin/console ca:cl with memory_limit=-1 fixed the problem, though it took a very long time for it to finish. After setting a breakpoint in this compiler pass and fixing that service definition bin/console ca:cl went back to only taking a few seconds to finish again. When I replaced the code for this compiler pass with the one prior to this change and then tried running bin/console ca:cl with the errored service definition it also went back to taking just a few seconds. So this PR is definitively the culprit, it looks like some loop there is not exactly infinite but takes a very long time to finish.

Please open a dedicated issue and provide a reproducer (even a private one you'd send me on Slack). Commenting on closed PRs doesn't work since we can't track those.

Please also let me know if the following patch has any effect on your side, both in terms of memory and time:

--- a/DefinitionErrorExceptionPass.php
+++ b/DefinitionErrorExceptionPass.php
@@ -71,7 +71,7 @@ class DefinitionErrorExceptionPass extends AbstractRecursivePass
                     }
                 }
 
-                unset($this->sourceReferences[$id]);
+                unset($this->sourceReferences[$id], $this->targetReferences[$id]);
             }