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From: "Jon Bills" <jon_bills AT hotmail DOT com>
Newsgroups: comp.lang.c++,comp.os.msdos.djgpp
Subject: Re: ** Pointer thingie's <= what's up with the double *?
Date: Fri, 14 Dec 2001 15:35:45 +0000 (UTC)
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"A. Sinan Unur" <asu1 AT cornell DOT edu> wrote in message
news:Xns917766F857AB6ASINANUNUR AT 132 DOT 236 DOT 56 DOT 8...

> "Mike Pilat" <pilat AT uiuc DOT edu> wrote in
> news:wTmS7.3829$tg4 DOT 48021 AT vixen DOT cso DOT uiuc DOT edu: 
> 
> > "A. Sinan Unur" <asu1 AT cornell DOT edu> wrote 
> >> "Emile Bosch" <emilebosch AT hotmail DOT com> wrote  
> >> > void** ptr; //? Double **?
> >>
> >> i don't think that is valid.
> >> AFAIK, you can't have pointers to void pointers. 
> > 
> > You can indeed have void**... for example, the COM IUnknown method
> > QueryInterface(..) takes a void** as a parameter into which your
> > interface pointer goes.
> 
> See http://www.eskimo.com/~scs/C-faq/q4.9.html

That's the C FAQ. The rules for pointer-to-void are different for C++.

If the OP hadn't cross-posted, we wouldn't have this confusion. From
a C++ perspective, there is nothing wrong with void** type. You can't
do much with it until it's cast to a particular type. It's a pretty
bad idea to use void** in C++ as it completely bypasses the type safety
system.

Note that assigning a pointer-to-void to pointer-to-type in C++ requires
a cast.

Jon.


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