I've been debugging a use-immediately-after-free bug involving obstacks (the bug isn't in trunk; I found it whilst testing one of my patches).
It was only visible as a crash when it happened that the call to obstack_free led to the underlying buffer being freed. Most of the time, the bug was dormant, since the obstack_free was merely unwinding the "high water mark" of allocation within a buffer, and so the "obstack_free"d memory was still accessible to the process. Is there a way to make the obstack code "fussier" e.g. a debug option that on obstack_free fills the freed memory with a canary garbage value, so that this kind of bug immediately leads to a crash? (probably only in a checking build). Similarly, filling obstack memory with "not-yet-initialized" etc. I wonder if there's a way to "teach" valgrind about obstacks. I can try my hand at a patch if people think it's a good idea. It's part of libiberty, so which mailing list "owns" obstack development? Thanks Dave
