Re: [boost] boost/checked_delete.hpp

Subject: Re: [boost] boost/checked_delete.hpp
From: Peter Dimov (pdimov_at_[hidden])
Date: 2009-06-08 09:52:28

Kizza George Mbidde:
...
>    typedef char type_must_be_complete[ sizeof(T)? 1: -1 ];
>    (void) sizeof(type_must_be_complete);
>    delete x;

...

> * What's the result of applying sizeof to an incomplete type?

A compile-time error, unless the compiler chooses to return 0 as a 
nonstandard extension.

> * Why is sizeof called twice?

The second sizeof is a workaround for a Metrowerks CodeWarrior bug in which 
the first typeof is never instantiated unless used.

> * Why is the result of sizeof cast to void? What exactly does that line 
> do?

Silences a compiler warning.

> * Is it an empty statement if the sizeof is legal?

Yes.

> * Why not apply x = 0; at the end?

It wouldn't do anything as x is passed by value.

--
Peter Dimov
http://www.pdplayer.com