[c++-pthreads] Re: pthread_cancel and EH: let's try this again

[Peter Dimov]

Alexander Terekhov wrote:
> Peter Dimov wrote:
> [...]
>> I don't get it. What is this code supposed to achieve?
>
> It's a dtor. The logic is this:
>
> Detect whether unwinding caused by cancel delivery is taking place
>
>  yes:
>
>    reassert cancellation;
>    invoke fclose() -- it will throw (and most likely not flush),
>      but will close/free resources nevertheless;
>    catch and finalize cancel exception;
>
>  no:
>
>    invoke fclose() fully prepared to hit cancel, and if canceled
>    (see above) simply reassert cancellation;


And what is gained compared to

~X() throw()
{
    fclose( file );
}

?

Not that fclose should be a cancellation point, of course.

Do you mean something along the lines of

~X() throw()
{
    try
    {
        lengthy_or_blocking_operation();
    }
    catch( ... )
    {
    }
}

where one would want to have cancellation enabled in 
lengthy_or_blocking_operation, even when ~X is called by stack unwinding?

I'm not sure how compelling is this example.