On Thu, 2007-11-01 at 08:35 +0900, Miles Bader wrote: > "Kaz Kylheku" <kaz@xxxxxxxxxxxxxxxxx> writes: > > This should be diagnosed by -Wunused, IMHO. You are calling a > > constructor, but ignoring the return value. > ... > > into the program, -Wunused will give you a diagnostic. But if you > > construct an object and ignore the result, you don't get a diagnostic. > > Of course constructors (and destructors) can have side-effects, and it's > not that uncommon to create objects just for such side-effects. I'm not > sure how common it is to use _unnamed_ objects in this way (I've never > done it I think, and it seems ever so slightly dodgy), but obviously it's > possible... > > I guess gcc could warn when there are obviously no side-effects but who > knows how easy that is (and maybe the few cases it catches aren't worth > the effort). In this case that would not work, since the constructor does have a side effect. What's more, the incorrect coding I used has a useful side effect: locking and then unlocking a mutex acts as a memory barrier. It just wasn't what the class was designed for, it was supposed to hold the mutex in a longer scope. The 'explicit' keyword helps prevent some problems, but I don't see that it useful here. -- John Skaller <skaller at users dot sf dot net> Felix, successor to C++: http://felix.sf.net
