Re: UB when flowing off end of value-returning function
"Scott Meyers" <NeverRead@aristeia.com>
Both C++98/03 and draft C++0x say this:
Flowing off the end of a function is equivalent to a return with no
value; this results in undefined
behavior in a value-returning function.
Does anybody know why this is undefined behavior instead of a hard error?
What kind of error? Compile-time -- forcing bogus return near the end when
the programmer has no intention ever reach that point? Or runtime -- say
emitting call to terminate? Well, the latter could be done, and I doubt it
would add much noise, but I don't see much benefit.
The compilers I use (VC, gcc) emit warnings 'not all control paths return a
value', catching most real problems, and flag some false positives.
It has an interesting implication for lambda expressions. Lambdas
declaring a return type but returning nothing yield UB and, with the
compilers I tested, don't necessarily issue a warning:
auto f = []()->int { std::cout << "Oops, I forgot to return
something"; };
That's an interesting observation. I'd expect a diagnostic. Do they declare
the new features as finished or yet experimental? I'd guess the latter and
in release form the warning will be there.
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