Valgrind is a popular and powerful tool for debugging programs and especially their use and abuse of memory.
runtests.pl automatically detects if valgrind is installed on your system
and by default runs tests using valgrind if found. You can pass -n to
runtests to disable the use of valgrind.
Valgrind makes execution much slower, but it is an excellent tool to find memory leaks and use of uninitialized memory.