FastMM4 says “The block header has been corrupted”

Question

I had this nasty bug that disappeared in the past but now after quite some time it returned.

I have two TSam objects (derived from TPersistent) created and loaded into a

Answer 1

There might be a logic race somewhere in the code where an object is being written to as it's being freed. Add NULL-checks and other IPC mechanisms (lock lists etc) to make sure that isn't the case.

Another option could be to subclass the code to add logging to it - and check whether objects are being sequentially accessed.