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

[David Pfitzner <dwpfitzner@xxxxxxxxx>]

Falk Hueffner <falk.hueffner@xxxxxxxxxxxxxxxxxxxxxxxx> wrote: 

> David Pfitzner <dwpfitzner@xxxxxxxxx> writes:
 
> > 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?
> 
> I don't think this is guaranteed to work. But I really don't know of
> *any* platform where it wouldn't work. While it is pretty common that
> pointers take more bits than ints, the opposite would be very weird.
> 
> > Eg, could you have a platform on which a particular int bit pattern
> > happened to be invalid as a pointer value, and the implementation
> > happened to notice this at runtime and throw up its hands in
> > horror?
> 
> It's not usual for compiled C programs to do such checks...
> 
> BTW, the Athena widget set and gtk make the assumption that this
> works all the time, and there haven't been any problems so far.

Right, its probably safe enough.  

I notice glib does have wrappers GINT_TO_POINTER(),
GPOINTER_TO_INT(), (along with definig gpointer and gint themselves),
which could perhaps be used to work-around obscure platforms
(ie, in general, not for Freeciv, since may not always have glib.) 

So to answer the original question, I may have been responsible for 
some such code, on the basis that I _knew_ allocating would work, 
compared to wasn't so sure about doing it "directly".

-- David

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