🚀 go-pugleaf

Eugene Lazutkin wrote:
[auto_ptr]

> It's good if you are going to create a STL
> container of auto_ptr's.  

	EGADS! NEVER DO THIS!!!!

	The following will CRASH FOR SURE:

	void f(vector<auto_ptr<X> >){}
	vector<auto_ptr<X> > vx; vx.push_front(new X);
	f(vx);
	vx[0]; // CRASH

Copying the container transfers ownership to the NEW container.
You must NOT use FIFO/block structure here: if the new
container is destroyed before the old one, all the auto_ptrs
in the old container dangle.

Even worse, if you have an input iterator onto the container
which returns an rvalue, dereferencing it steals ownership
from the container by creating a copy -- the destruction
of which will delete the object, leaving the container's
auto_ptr dangling. 

[Correct use of the idiom requires the newest copy of
an auto_ptr outlive use of older ones. This is often
achieved by assigning the newest value back to the object
it was copied from.]

-- 
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81 Glebe Point Rd              fax:   61-2-660-0850
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AUSTRALIA                      email: skaller@maxtal.com.au

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