[c++-pthreads] Re: thread-safety definition

[Matt Austern]

On Jan 12, 2004, at 5:41 AM, Dave Butenhof wrote:

> I think I disagree, at least philsophically, with the characterization 
> of the model as "fragile". But I think I also understand what you 
> mean; and the problem isn't with the model, but rather with the effect 
> of that model on existing code that all-too-casually and agressively 
> eats exceptions it doesn't understand. I think there are vanishingly 
> few circumstances where a blind catch(...) without an unconditional 
> re-throw should be considered "legitimate". If you don't completely 
> understand what an exception means, you cannot claim to have 
> completely recovered, and therefore cannot reasonably finalize 
> propagation. (And when you catch anonymously, you can't possibly 
> understand what they mean since you can't even identify them.) On the 
> other hand, regardless of whether the semantics are meaningful or 
> reasonable, the syntax is legal and apparently (unfortunately) in 
> common use, so I can't dispute that you need to consider that.

One legitimate use for that pattern is in mixed-language programming, 
when you write a little adapter to turn the error reporting mechanism 
used by the C++ part into an error reporting mechanism that the C part 
can understand. I think that's reasonable for most of the things 
exceptions are used for.  It isn't reasonable for thread cancellation, 
because C needs to know about thread cancellation too.  (Maybe this 
means that thread cancellation isn't quite "error reporting".)

It looks to me like most of the recent discussion has come back to 
catch(...).  I wonder if that's really the fundamental problem we have 
to solve?

			--Matt