[boost] Re: boost::execution_monitor impl under windows

From: David Abrahams (dave_at_[hidden])
Date: 2003-10-08 13:09:47

Alexander Terekhov <terekhov_at_[hidden]> writes:

> David Abrahams wrote:
> [...]
>> I asked David Butenhof to explain the issue since I couldn't get any
>> other explanation.  We had a long discussion about it.  Basically, the
>> conclusion I (we) came to was that 2-phase EH is a good QOI choice as
>> a workaround for platforms where exception throwing due to
>> "asynchronous" interrups like crashes and signals has been instituted,
>> but that mandating it in the standard would be a mistake, because it
>> provides very few advantages on other platforms, and there is no
>> advantage to that kind of crash=exception throwing in the first place.
>
> How many times do I need to repeat that the issue here is unneeded
> and *hurting* unwinding for ANY unexpected exception -- "normal" C++
> "throw-expressions" including. 

Maybe until everyone understands why it hurts so badly.

> I have THE APPLICATION that doesn't
> handle std::bad_alloc because it documents its address space size
> requirements and all std::bad_alloc's are either "admin errors" or 
> indications of some serious flaw (leaking, corruption, whatever). I 
> neither *really want* nor *really can* wrap all "operator new(size_t)
> and "operator new[](size_t)" calls with catch(const std::bad_alloc&) 
> { abort(); } (or replace them with std::nothrow_t stuff and "if").

No, but you can replace operator new so that it aborts on failure.

>> The sorts of advantages that apply everywhere are relegated to
>> debugging relatively obscure conditions, e.g., that it may be easier
>> to debug an exception-specification violation that the runtime can
>> detect will be violated at the throw point, since the program can core
>> dump 
>
> and, more importantly, failover...

I don't see how failover (switching to backup hardware) can help with
what you claim is a programming error.

>>      immediately.  
>
> Right. Some optimizations would be possible too.

Example?

>> But not all ES violations can be detected that way.
>
> Really? Such as? Please elaborate.

I'm holding your answer as a hostage in exchange for an understandable
description of the optimization you think is enabled by 2-phase EH.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com