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

AI;DR – This blog post and the debug memory manager it describes were developed with significant help from Claude. If you don’t want to read “AI slop”, stop reading now. I recently added a new import functionality to the GExperts Code Librarian. During the test phase I found a nasty (preexisting) bug: After deleting a folder branch, the whole file became corrupted. On the next open it failed with a “Stream Read Error”. Deleting the branch had shown no error at all. From the user’s point of view the deletion had simply worked. This happened in Delphi 6, the most ancient version that GExperts still supports. The Code Librarian stores its snippets in a single-file container based on Primoz Gabrijelcic’s GpStructuredStorage. A “Stream Read Error” on open means the container’s internal directory is inconsistent, so something had corrupted the file during the delete without complaining. Reproducing it The first step was a tiny console program that builds a storage file with a folder tree,…