A few months back, I wrote about wanting a warning from C++, and not being able to get one. It happened again.

We have code like this:

class CMyString
{
    /** Return a copy of the string with outlying spaces removed. */
    CMyString Trim() const;
};

If you read the comments and signature of the Trim() method, you see that it returns a copy of the string. But if you are less careful, you can think that this method trims the string in place:

CMyString fooey("  this needs trimming.   ");

fooey.Trim();                       // bad
CMyString good = fooey.Trim();      // good

I figured, there ought to be a way to get a compiler warning: not only is the return value ignored, but the method is declared const, so it conceptually has no side effects. I know: the const aspect can be worked around, but still, why can't the compiler warn me about this?

There's a warning that can tell me that I've used an enumeration type in a switch, and have not provided a case for every enumeration value. This warning will appear even if there is a default clause! If this is something that can be warned about, why not ignoring the return from a const method?