Re: lua_number2int

[David Jones <drj@...>]

On 15 Nov 2006, at 00:39, David Given wrote:

> Brian Weed wrote:
> [...]
> > So, to be safe, maybe I should do this?
> >
> > #define lua_number2integer(i, d) ((d) < 0 ? (i) = (int)(d) : (i) =
> > (int)(unsigned int)(d))
>
> Actually, I think the only way to be completely safe would be to do:
>
>
> int lua_number2integer_f(double d)
> {
> 	if (d < INT_MIN)
> 		return INT_MIN;
> 	if (d > INT_MAX)
> 		return INT_MAX;
> 	return (int)d;
> }
>
> #define lua_number2integer(i, d) i=lua_number2integer_f(d)
>
>
> ...but that's rather a mouthful, and of course you'd need a completely
> separate version for unsigned ints.

I think you're right; this is the only safe way.  I'm amazed that  
this has gone unnoticed.  Of course, even with this solution it's  
_possible_ to construct a perverse C implementation where it would be  
undefined behavious (if INT_MAX was huge enough to be outside the  
range of double).

drj