Naive reverse string iteration infinite loop and/or assertion failure C++ / Visual Studio 2022

Question

I am trying to reverse iterate through a string, but am getting assertion failure for the [] operator in the latest VS.

int foo() {
    std::string s = "s";
    for (int i = (s.size() - 1); i >= 0; i--) {
        std::cout << s[i] << std::endl;
    }
    return 0;
}

Commenting out the cout line gives infinite loop warning and indeed enters infinite loop:

int foo2() {
    std::string s = "s";
    for (int i = (s.size() - 1); i >= 0; i--) {
        //std::cout << s[i] << std::endl;
    }
    return 0;
}

Iterating forwards works just fine with or without anything in the for loop:

int bar() {
    std::string s = "s";
    for (int i = 0; i < s.size(); i++) {
        std::cout << s[i] << std::endl;
    }
    return 0;
}

I am using the C++14 standard and the same code used to work on other compilers/older versions of VS. The same problem exists for any string size (although that should be irrelevant). I understand I could modify the code to use and dereference pointer instead of using int, but want to understand why this doesn't work anymore, why is it unsafe or incorrect, or what else am I missing. Thanks!

Answer 1

Could it be that your int defaults to being unsigned and therefore decrementing when i=0 resuts in a high value ?

As @PeteBecker mentioned, int should be signed and should not overflow. However my guess is that your actual code does not use int.