Re: [boost] [exception] uncaught_exception_count, scope(failure), scope(success)

Subject: Re: [boost] [exception] uncaught_exception_count, scope(failure), scope(success)
From: Evgeny Panasyuk (evgeny.panasyuk_at_[hidden])
Date: 2013-02-05 16:23:54

06.02.2013 0:40, Emil Dotchevski:

> I'm not an expert on D but Google tells me that it doesn't support
> automatic deterministic termination.

Could you please describe what do you mean?

> So, if you have a file or a
> handle open, you need scope(exit) to close it. It also means that the
> programmer must keep track of all non-memory resources and dispose
> them "manually" like a C programmer.

> In C++, RAII makes scope(exit) unnecessary,

While scope(exit) is some kind of ad-hoc replacement for RAII wrappers, 
scope(failure) and scope(success) are not.
Nowadays scope(failure) and scope(success) are emulated in C++ via 
ScopeGuard idiom.

For motivating examples check:

ScopeGuard: 
http://www.drdobbs.com/cpp/generic-change-the-way-you-write-excepti/184403758#

scope(failure)/scope(success):
http://channel9.msdn.com/Events/Lang-NEXT/Lang-NEXT-2012/Three-Unlikely-Successful-Features-of-D 
,
http://channel9.msdn.com/Shows/Going+Deep/C-and-Beyond-2012-Andrei-Alexandrescu-Systematic-Error-Handling-in-C 
(ScopeGuard11 part)

 > and catch(...) is the same as scope(failure).

Compare:

scope(failure)
{
     rollback1();
};
do1();
scope(failure)
{
     rollback2();
};
do2();
scope(failure)
{
     rollback3();
};
do3();

with

try
{
     do1();
     try
     {
         do2();
         try
         {
             do3();
         }
         catch(...)
         {
             rollback3();
             throw;
         }
     }
     catch(...)
     {
         rollback2();
         throw;
     }
}
catch(...)
{
     rollback1();
     throw;
}

-- 
Evgeny Panasyuk