Re: [boost] [thread] catch(...) removed

From: Ulrich Eckhardt (doomster_at_[hidden])
Date: 2006-07-16 09:06:33

On Thursday 06 July 2006 15:45, Peter Dimov wrote:
> -        try
> +//        try
>          {
>              thread_param* p = static_cast<thread_param*>(param);
>              boost::function0<void> threadfunc = p->m_threadfunc;
> @@ -115,12 +115,12 @@
>              on_thread_exit();
>  #endif
>          }
> -        catch (...)
> -        {
> -#if defined(BOOST_HAS_WINTHREADS)
> -            on_thread_exit();
> -#endif
> -        }
> +//        catch (...)
> +//        {
> +//#if defined(BOOST_HAS_WINTHREADS)
> +//            on_thread_exit();
> +//#endif
> +//        }

This is really bad. It deactivates some code instead of removing it without 
the least comment why it is still there. What is the next person maintaining 
supposed to think? No, instead of doing this you should add a comment that 
says that a first approach (and an earlier version) used to catch(...) but 
that this effectively prevents invocation of the debugger and is therefore a 
bad idea.
An exception coming up here is a programming mistake anyway and hiding this 
silently here is bad because it restricts the user's possibilities. And they 
can still catch(...) in their code.
Also, not even catching(...), calling on_thread_exit() and rethrowing is an 
alternative because at that time the stack is already lost and if an 
exception propagates up there it would invoke std::terminate(). It thus 
prevents jumping into the debugger as noted above.

Referring to another posting in this thread, where you try to achieve the same 
via a local object's destructor, there is possibly a mistake in that: AFAIK, 
when an exception is thrown and not caught, terminate() is invoked without(!) 
unwinding the stack, or am I confusing something?

cheers

Uli