Omitting return statement in C++

I just had some weird behavior from a version of g++ for Windows that I got with Strawberry Perl. It allowed me to omit a return statement.

I have a member function that returns a structure consisting of two pointers, called a boundTag:

struct boundTag Box::getBound(int side) {
    struct boundTag retBoundTag;
    retBoundTag.box = this;
    switch (side)
    {
        // set retBoundTag.bound based on value of "side"
    }
}

This function gave me some bad output, and I discovered that it had no return statement. I had meant to return retBoundTag but forgot to actually write the return statement. Once I added return retBoundTag; everything was fine.

But I had tested this function and gotten correct boundTag output from it. Even now, when I remove the return statement, g++ compiles it without warning. WTF? Does it guess to return retBoundTag?