Re: UB when flowing off end of value-returning function

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 3 Nov 2010 09:19:36 -0700 (PDT)

Message-ID:

<3dd05921-9fc4-4a33-8e7b-1fbe117cb9af@l17g2000yqe.googlegroups.com>

On Nov 2, 6:49 pm, Leigh Johnston <le...@i42.co.uk> wrote:

On 02/11/2010 18:39, Juha Nieminen wrote:

Leigh Johnston<le...@i42.co.uk> wrote:

[...]

     int foo()
     {
         bar();
         assert(false);
     }

"This way if it was a mistake, like it probably was, it will
be caught pretty fast."

I assume that since the standard says it's undefined
behavior, the compiler *is* allowed to do that.

It is.

Yes Balog suggested issuing a runtime error else-thread and
said s(he) couldn't see much benefit; neither do I if I am
honest. Undefined behaviour includes crashing and one has to
expect crashes when one creates bugs. :) The argument in
favour of what you suggest is the insidious possibilty of UB
silently working resulting in undiscovered bugs. I guess this
is a QoI issue.

The problem is that for return types like int, the code probably
will work, but with a random value (whatever happened to be in
EAX on an Intel, for example). Catching such errors would be
useful; they're probably more frequent (and less expensive to
catch) than a lot of errors debugging implementations currently
catch.

--
James Kanze