This is Memory Allocation Checker package.  Main features:
* Fault on pointer overrun (read or write).
* Fault on freed pointer dereference (read or write).
* Log double free or realloc of already freed pointer.
* Log memory not freed on exit.
* Check for pointer underrun on free/realloc.
* Optionally reverse behaviour of overrun and underrun.
* Optionally "churn" reallocations. Always return a different pointer.
* Optionally log pointer overruns instead of faulting.
* Optionally return freed memory to system. (May hurt checking for freed
  pointer usage).
* Very small performance impact.
* Large memory footprint impact.
* Includes a validation test suite to test correctness of libmemcheck.

WWW: http://www.sound.net/~hald/projects/memcheck/