Re: [boost] Has someone any plans to submit a exception_ptr library to Boost?

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-04-15 14:24:01

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On Tuesday 15 April 2008 13:19 pm, Sebastian Redl wrote:
> Peter Dimov wrote:
> > Note that N2179 doesn't require a copy to be made. If GCC allocates the
> > exception objects on a heap - I have some recollections that it was doing
> > that but I may be wrong  - it might still be possible to implement
> > current_exception to return a pointer to the active exception object...
> > if there's a way to insert a reference count somewhere inside.
>
> I took a larger stab at this, but I'm pretty much stumped right now. I
> can't abuse the reference count in __cxa_exception, because if I do, the
> handled exception stack won't be properly cleaned up.

I've never worked with compiler-internal kinds of things, but here's my 
attempt at a helpful suggestion.  Instead of modifying the reference count, 
is it possible to do anything with the 
__cxa_exception::unwindHeader.exception_cleanup function pointer?  Maybe you 
could replace it with something that doesn't actually destroy the exception 
object, and then have the exception_ptr take ownership.  You also have access 
to the exception's destructor with the __cxa_exception::exceptionDestructor 
function pointer, although I think even if you replaced this with a null 
destructor, it would still free the memory for the exception object.

- -- 
Frank
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