Re: [boost] [Thread] Win32 exception handling

Subject: Re: [boost] [Thread] Win32 exception handling
From: David Abrahams (dave_at_[hidden])
Date: 2008-11-25 16:11:54

on Tue Nov 25 2008, "Emil Dotchevski" <emil-AT-revergestudios.com> wrote:

> On Tue, Nov 25, 2008 at 12:26 PM, David Abrahams <dave_at_[hidden]> wrote:
>> on Tue Nov 25 2008, "Emil Dotchevski" <emil-AT-revergestudios.com> wrote:
>>> Maybe I'm missing something but what in the upcoming standard requires
>>> the catch(...)?
>>
>> The requirement that terminate() be called when the exception isn't
>> otherwise caught.  Of course you can do it with "compiler magic" because
>> the standard doesn't specify an implementation.  Practically speaking,
>> though, it means a catch(...) in the library.
>
> I don't follow.
>
> It means that no exception should propagate out of the thread
> function. 

It means more than that.  It means that terminate() is called.

  "If no matching handler is found, the function std::terminate() is
   called; ..."

> In other words, if an exception propagates out of the thread
> function, that's a bug. 

It's only a bug if your program doesn't expect to call std::terminate()
in that case.  If terminate() is your desired result, it's not a bug.

> In this case, the call to terminate() is reasonable. As a bonus, a
> standard-conforming implementation can also display a stack trace.

Yes, but catch(...) will prevent many existing implementations from
displaying a useful stack trace.

> Anyway, automatic catch(...) in boost::thread is not necessary IMO. 

It is necessary for conformance in many popular implementations because
they have no other way to ensure a call to terminate().

> To me that's like having an automatic catch(...) in main(). This
> doesn't mean that it's always a bad idea, only that the decision to
> use catch(...) is outside of the scope of boost::thread.

Not if Boost.Thread is trying to conform to the CD.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com