Valgrind

http://developer.kde.org/~sewardj/

Valgrind is a GPL'd tool to help you find memory-management problems in
your programs. When a program is run under Valgrind's supervision, all
reads and writes of memory are checked, and calls to
malloc/new/free/delete are intercepted. As a result, Valgrind can detect
problems such as:

    * Use of uninitialised memory
    * Reading/writing memory after it has been free'd
    * Reading/writing off the end of malloc'd blocks
    * Reading/writing inappropriate areas on the stack
    * Memory leaks -- where pointers to malloc'd blocks are lost forever
    * Passing of uninitialised and/or unaddressible memory to system
calls
    * Mismatched use of malloc/new/new [] vs free/delete/delete []
    * Some misuses of the POSIX pthreads API

-- 
Florin Andrei
"Some times are fuzzier than others." - Dan Farmer & Wietse Venema