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.

Valgrind can debug more or less any dynamically-linked ELF Linux x86 executable, without modification, recompilation, or anything, as long is it contains only classic x86 code (MMX/SSE/SSE2/3DNow! largely unsupported for the moment). There is experimental support for programs using libpthread.

Valgrind provides a generic infrastructure for supervising the execution of programs called "tools". This is done by providing a way to instrument programs in very precise ways, making it relatively easy to support activities such as dynamic error detection and profiling. Available tools include Memcheck (a heavyweight memory checker), Cachegrind (a cache-miss profiler), Addrcheck (a lightweight memory checker) and Helgrind (a data-race detector), among others.