Can (a==1)&&(a==2)&&(a==3) evaluate to true? (and can it be useful?)

Question

Inspired by another question regarding java-script language. Can the expression

 (a==1)&&(a==2)&&(a==3)

evaluate to true i

Answer 1

As it was noticed before, this trick could be performed with volatile. This is more honest approach compared to operator changing. Just let us use two threads:

volatile int a;

void changingValue(){
    std::srand(unsigned(std::time(0)));
    while (true) {
        a = (rand() % 3 + 1);
    }
}

void checkingValue(){
    while (true) {
        if (a == 1 && a == 2 && a == 3) {
            std::cout << "Good choice!" << std::endl;
        }
    }
}

int main() {
    std::thread changeValue = std::thread(changingValue);
    changeValue.detach();
    std::thread checkValue = std::thread(checkingValue);
    checkValue.detach();
    while (true){
        continue;
    }
}

Moreover, this code in my case is working well with no volatile declaration. As far as I understand, it should depend on compiler and processor. Maybe someone could correct it, if I'm wrong.