Re: [boost] [Boost.Thread]: consider removing catch(...) fromthread_proxy

From: David Abrahams (dave_at_[hidden])
Date: 2005-08-26 08:17:41

Matt Hurd <matt.hurd_at_[hidden]> writes:

>>On 25/08/05, John Maddock <john_at_[hidden]> wrote:
> <snip>
>> I think I'd come down on the other side: this isn't a minor change, it's a
>> complete change of semantics and we should be very careful about such a
>> change.  With most of the compilers I use an uncaught exception thrown from
>> a user thread will terminate the application, which may be what you want, or
>> it may not: but it sure is drastic!  You can always trap uncaught exceptions
>> yourself and call abort (or whatever) if that's what you want.  The debugger
>> I use will also let you trap all thrown exceptions if that's what you want,
>> whether they all do that I don't know.
>> 
>> Also 2c worth,
>
> After thinking about it some more, I'd still much rather see a
> screaming application halt than the false sense of security suggested
> by silent failure.  

If that's what you want, you ought to force it to halt.  Probably the
most reliable way is to put an empty exception-specification on the
function and make sure it's being called by another C++ function, just
for good measure.  Of course, you'd need to take special measures for
MSVC, which doesn't implement any runtime behavior for exception
specifications.

> Yes, it is a big change, and needs more comment. 
> As you suggest, you may catch anything in your own handler.  I worry
> that silent collection of exceptions will allow too many subtle errors
> to slip through, especially in the land of concurrency.  It has
> happenned to me that I've let errors slip through in pooled workers
> where I didn't notice rare failures and the loss of a single worker
> thread.  A screaming halt would have woken me up from my lazy
> stupidity...

Another possibility (a good one IMO) would be to allow a
user-replaceable handler there, which could abort, log a message and
then abort, eat the exception, etc., as desired.  If the default is to
eat the exception, you have perfect backward compatibility.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com