A discussion on Valgrind's capacity to detect undefined behavior:

Valgrind is *NOT* a leak checker

by Mark Isaacson

From the article:

Valgrind is one of the most misunderstood tools I know of in my community. Valgrind is not a leak checker. It has a leak checking tool. I'd argue that this tool happens to be the least useful component.

Without changing the way you invoke Valgrind, you get so much more useful information than most people realize. Valgrind finds latent bugs even when they don't cause your program to fail/crash; it doesn't just tell you where the bug happened, it tells you why it happened, in English. Valgrind is an undefined behavior checking tool first, a function and memory profiler second, a data-race detection tool third, and a leak checking tool last...