It's not simple to find the undefined behavior in C. (As evidenced by the OP being about a tool to help. I've read that clang may be better than gcc at this.)

It's not simple to find the undefined behavior in C. (As evidenced by the OP being about a tool to help. I've read that clang may be better than gcc at this.) For the sort of code that was best written in C, a few decades ago, it was often reasonable engineering to depend on technically undefined behavior. Then over the decades the compilers made increasingly-subtle transformations without getting much better at telling you where they might have tripped you up (again, maybe except for clang which I haven't tried yet).