[Freeciv-Dev] Re: int -> void*, was Re: [RFC] Attaching information to objects

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Wed, Jan 17, 2001 at 07:11:00PM -0800, David Pfitzner wrote:
> Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx> wrote: 
> 
> > On Mon, Jan 15, 2001 at 03:11:08PM -0800, David Pfitzner wrote:
> 
> > > Is it guaranteed by the language that stuffing the int into the
> > > void* will always work, or does it just happen to work on most
> > > (all?) platforms?
> 
> > ISO/ANSI C99 added optional types intptr_t and uintptr_t. Pointers
> > can be cast to these types and back without loss of information.
> > IMHO they are expected to be used in weird places where pointers
> > need to be stored together with integers
> 
> Well, I don't think Freeciv actually uses/requires C99 features
> at this time :-)

Configure can maybe teached to recgonize that intptr_t is available.

> Also this sounds like still a different problem, since it talks
> of casting pointers to int and back, where we're interested in
> casting arbitrary ints to pointers (specifically void*) and back.

So sizeof(int)<=sizeof(intptr_t). If you choose
sizeof(int)==sizeof(intptr_t) there will be no trouble either way.

        Raimar

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