TITLE: throw as the last line in a function

(Newsgroups: comp.lang.c++.moderated, 16 Nov 98)


NAGLE: nagle@netcom.com (John Nagle)
>
>    One of those language lawyer questions.
>
>	int foo()
>	{
>		...
>		throw("msg");
>	}
>
>    "throw" cannot return, so it should not be followed by another
>statement.  Thus there's no "return" statement at the end of the
>function.  Some compilers don't like that.  What's correct?
>
>    It's one of those annoying things where, either way, some
>compiler probably won't like it.


CLAMAGE: clamage@Eng.Sun.COM (Steve Clamage)

If every execution path through the function winds up at
the throw statement, the function return type should be
void, not int, since it can't return a value. :-)

More likely, the throw statement is conditional, and some other
path finds a return statement.

However, your scenario can occur if foo is virtual and you
want to indicate an error by throwing an exception if this
particular version of foo is called.

One alternative is to make the function pure virtual.

If that is not appropriate for some reason, put a return statement
after the throw. In the worst case, a compiler will warn about
unreachable code. Unreachable code is not a violation of any
language rule, so no compiler should reject a program merely
because it contains unreachable code. OTOH, no compiler is
required to do the flow analysis to determine that a statement
cannot be reached, so you are more likely to get a rejection due
to a "missing" return statement.