Re: nmap 3.3+V-2.99

[Brett Hutley <brett () hutley net>]

Jay Freeman (saurik) wrote:

> Brett:
>
> Counted_ is defined to be a pointer. The only two expansions are:
>
> template <typename Counted_>
> class ReferenceManager :
>     public NullReferenceHelper<Counted_ *>
> {
>   public:
>     // XXX: stupid gcc 3.2.2
>     typedef typename NullReferenceHelper<Counted_ *>::Value Value;
>
> This is a backend function of a massively generalized smart pointer class.
> The particular implementation of Clear being looked at is defined in a
> helper class that reference count managers that are managing pointers are
> encouraged to derive from for easier implementation. If you needed a smart
> pointer that worked over something else (maybe more smart pointers, maybe
> the windows HANDLE sysem, etc.) then you could implement your own version of
> Clear() that resets the value to a cleared state. In this case, simply
> setting it to NULL works.
>
> Your point about the callers being broken is what seems would have to be the
> case considering A) if it weren't something you could assign NULL to it
> wouldn't compile and B) assigning NULL to something that can be assigned
> NULL to wouldn't crash except if your reference to that object was invald
> and then reading the reference (such as Gisle's patch does) would also cause
> the same crash (well, unless the reference you have is in read only memory
> or something and also happens to be set to 0s, but I have hardly ever seen
> readonly memory used...).

Yes. I figured that Value was a smart pointer class, but rather than 
implementing with templates, I was assuming that it was implemented 
using a class with the assignment operator overloaded.
That's why Gisle's patch looked so odd (at least with regard to the 
changes to the Clear() function.

--
Brett Hutley [MAppFin,CISSP,SANS GCIH]
mailto:brett () hutley net
http://hutley.net/brett



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