Re: vector<> can probably never grow to it's maximum size!

[Dhruv Matani <dhruvbird at gmx dot net>]

This patch seems more correct, because it handles the case where the
memory in fact can be allocated.

-Dhruv.

On Tue, 2004-10-19 at 22:04, Dhruv Matani wrote:
> On Tue, 2004-10-19 at 20:44, Paolo Carlini wrote:
> > Dhruv Matani wrote:
> > 
> > >And tries to explain more concretely what I'm trying to achieve and also
> > >shows that it's do able in current C++.
> > >
> > Why you keep on refusing to deal with one issue at a time?
> 
> I know :-( I have to try and consciously stick to one thing at a time,
> and learn to control my frivolous nature.
> 
> > 
> > The below cannot fix, not even in principle, the immediate problem that
> > we have with __len overflowing size_type: all the new tricks in __mt_alloc
> > are not in effect in this case, ::operator new for sure will never return
> > an address == _M_start (half the memory is already used), it will always
> > throw, even if you ask only for __old_size + 1. 
> 
> Ah! I did not think about this. You are right on this count because
> vector first allocates and then deallocates, so no matter what if half
> the memory is used, you are doomed.
> 
> > Don't try to achieve the
> > impossible, concentrate on the case of small memory allocations, managed
> > via mt_alloc memory pools: in that case there is rooom for improvement..
> 
> Yes, I have shown in the patch that the small size cases can be dealt
> with quite well with __mt_alloc<>.
> 
> 
> Attached is a patch and test-case which shows that the patch actually
> works.
> 
> > 
> > Paolo.
-- 
        -Dhruv Matani.
http://www.geocities.com/dhruvbird/

The price of freedom is responsibility, but it's a bargain, because
freedom is priceless. ~ Hugh Downs

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