Creating a dangling const pointer is pretty trivial. Hell, make it a const reference.

    #include <iostream>

    struct Foo {
        const int &dangling;

        Foo(const int &dangling): dangling(dangling) { }
    };

    Foo foo() {
        int dangling = 0;
        Foo foo(dangling);
        return foo;
    }

    int main() {
        std::cout << foo().dangling << std::endl;
        return 0;
    }

Neither g++ nor clang warn on this, either. I am not sure why you think const pointers are safe. They aren't. Flat out.