1. 2014

    On compiler warnings (and off them, too)

    Quick, what’s wrong with this C++ program?

    #include <iostream>
    int test(int arg) {
        cout << arg << endl;
    int main(int argc, char** argv) {

    Did you guess nothing at all? Because that’s what GCC says:

    $ g++ -o funnyprogram funnyprogram.cpp


    Pretty much every other programming language that makes you explicitly identify a function’s return type will also make you actually return something from that function. C and C++ don’t, and furthermore GCC doesn’t even warn you that anything is wrong. This can occasionally lead to serious bugs, as I discovered today in this real-world example. I had a function that checks the name of an object and returns an enum value based on that name.

    virtual const HardFactorOrder get_order() const {
        // relies on a particular convention for get_name()
        // but can be overridden for hard factors where that convention doesn't apply
        std::string name = get_name();
        if (name.compare(0, 3, "H01") == 0) {
            return MIXED;
        else if (name.compare(0, 2, "H0") == 0) {
            return LO;
        else if (name.compare(0, 2, "H1") == 0) {
            return NLO;

    That was all good when all the objects involved had names conforming to the convention, but my latest batch of updates to …