How to catch glaring undefined behavior statically?

Question

I'm using clion and I'm running some code that has UB. My goal is to catch it statically:

#include <iostream>
#include <vector>



int main() {
    auto v = std::vector<int>();
    v.push_back(20);
    auto &first = v[0];
    auto vector_ref = &v;
    vector_ref->clear();
    std::cout << first;

}

This is UB, and I'm trying to catch it.

I have added the following to my cmake project:

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=undefined -O1 -fno-omit-frame-pointer -g")

I still get no warnings.

what do I have to enable so that I can catch such UB instances?

Answer 1

Some compilers can detect some UB statically. No compiler is required to detect any UB except in some cases specified in the standard (in constant expressions).

what do I have to enable so that I can catch such UB instances?

Best you can do is to enable all warnings. If the compiler doesn't detect it, then modify the compiler to do so. This may be either very difficult, or very expensive in compile time, or both.

Sanitisers can help only at runtime.