Valgrind (Which also has a bunch of other stuff like cachegrind, which can be a godsend if you are getting telltale cache/branch prediction issues but you can't find where etc.).

Clang/GCC both have suites of sanitizers which are usually excellent and easy to grok, these are also available in many language frontends based on LLVM (and maybe GCC?)

You can just throw every tool you can find at your CI if you're paranoid, too.