How to debug a crash that only occurs on application shutdown? (Delphi)

Question

So, after some recent changes we discovered that one of our oldest applications is sometimes crashing on shutdown. This manifests itself either in the form of \"Runtime error 21

Answer 1

Like others said: 216 means AV after SysUtils was shutdown. Usually, the only thing that shutdowns after SysUtils (and have chance to raise AV) - is System unit. Specifically: memory manager.

So, run-time error 216 at shutdown usually means memory corruption bug in your application.

That can be very easy to solve - just enable full debug mode in memory manager or use a debugging memory manager. Sometimes, however, it can be very hard to find. But you can start with debug mode of MM first.

See this article.