Hunting a GExperts Code Librarian corruption bug with a custom debug memory manager

This article details the process of hunting down a preexisting corruption bug in the GExperts Code Librarian, which caused file corruption after deleting a folder branch in Delphi 6. The author describes reproducing the issue, identifying it as a use-after-free error, and developing a custom debug memory manager (DebugMM.pas) to catch the invalid memory access. The solution involved wrapping the existing memory manager with sentinel values and stack traces, leveraging Claude AI for assistance. The bug was version-independent, and the fix applies across Delphi versions. This is a technical debugging and software engineering article focused on memory management, Delphi programming, and tool creation.