[perl #39855] [CAGE] configuration: define MIN/MAX macros for all integral typedefs

[Nicholas Clark]

On Sat, Apr 18, 2009 at 12:09:10AM -0700, Christoph Otto via RT wrote:
> On Wed Aug 06 20:07:05 2008, Whiteknight wrote:
> > On Sat May 17 14:57:18 2008, pmichaud wrote:
> > > On Mon Jul 17 11:59:47 2006, chip wrote:
> > > > It's great to have INTVAL and UINTVAL, but without MAX_INTVAL it's
> > kind of
> > > > hard to work with them in some respects.  All integral typedefs should
> > > have
> > > > min/max macros.  Syntax not a big deal, it can be fixed later, just
> > don't
> > > > break anything when introducing them.
> > > 
> > > Nothing has happened on this ticket since it was introduced in 2006.  Do
> > > we need MIN/MAX macros?  If so, why, or where do we expect them to be
> > used?
> > > 
> > > Pm
> > 
> > Defining them on a 2's complement machine would be easy as pie:
> > 
> > #define MAX_UINTVAL (UINTVAL)((INTVAL)-1)

I think that that would be better defined in terms of ~0

> > #define MIN_UINTVAL (UINTVAL)0

This one, I think is correct.

> > #define MAX_INTVAL  (((INTVAL)-1) / 2)

Eh? -1/2 is 0 for signed integer arithmetic.

> > #define MIN_INTVAL  ((~MAX_INTVAL) + 1)

Even with the correct definition of MAX_INTVAL, that's going to be out by 1.
For a two's complement system, it doesn't need the + 1.

The logic that Perl 5 uses to do this is described here:
http://perl5.git.perl.org/perl.git/blob/HEAD:/perl.h#l2178

I suspect it's portable.

Nicholas Clark