Eliminate class allocators and deallocators?

[Craig Black]

Andrei Alexandrescu Wrote:

> Michel Fortin wrote:
> > On 2009-10-06 20:26:48 -0400, Andrei Alexandrescu 
> > <SeeWebsiteForEmail at erdani.org> said:
> > 
> >> The matter has been discussed quite a bit around here and in other 
> >> places. I'm not having as much time as I'd want to explain things. In 
> >> short, destroying without freeing memory avoids dangling references 
> >> and preserves memory safety without impacting on other resources.
> >>
> >> It's a safety hack, not a performance hack.
> > 
> > In my opinion, it's mostly an illusion of safety. If you call the 
> > destructor on an object, the object state after the call doesn't 
> > necessarily respects the object invariants and doing anything with it 
> > could result in, well, anything, from returning wrong results to falling 
> > into an infinite loop (basically undefined behaviour). What you gain is 
> > that no object will be allocated on top of the old one, and thus new 
> > objects can't get corrupted. But it's still undefined behaviour, only 
> > with less side effects and more memory consumption.
> > 
> > I don't think it's a so bad idea on the whole, but it'd be more valuable 
> > if accessing an invalidated object could be made an error instead of 
> > undefined behaviour. If this can't be done, then we should encourage 
> > "destructors" to put the object in a clean state and not leave any dirt 
> > behind. But should that still be called a "destructor"?
> > 
> > Perhaps we could change the paradigm a little and replace "deletion" 
> > with "recycling". Recycling an object would call the destructor and 
> > immeditately call the default constructor, so the object is never left 
> > in an invalid state. Objects with no default constructor cannot be 
> > recycled. This way you know memory is always left in a clean state, and 
> > you encourage programmers to safely reuse the memory blocks from objects 
> > they have already allocated when possible.
> 
> Yes, recycling is best and I'm considering it. I'm only worried about 
> the extra cost.
> 
> Andrei

No this is a bad idea.  Removing the possibility to delete data will cause serious problems with heap fragmentation in some programs.

-Craig