Re: macro FIXNUM_OVERFLOW_P in lisp.h is valid ?

[Andreas Schwab <schwab@linux-m68k.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Stefan Monnier <monnier@iro.umontreal.ca>
>> Date: Fri, 23 Oct 2009 21:05:05 -0400
>> Cc: t_tuneyosi@hotmail.com, Andreas Schwab <schwab@linux-m68k.org>,
>> 	emacs-devel@gnu.org
>> 
>> Actually, when the cast was added in 2001, it came with the following
>> commit-log-comment:
>> 
>>   (FIXNUM_OVERFLOW_P): Cast I to EMACS_INT in comparisons
>>   in case I is of some unsigned type, in which case
>>   MOST_NEGATIVE_FIXNUM will be converted to unsigned, and the
>>   comparison becomes bogus.
>
> Right, sorry for my failing memory.
>
> So I think the change made yesterday by Andreas should be reverted.

These should also work with unsigned types, but may generate extra
warnings:

#define FIXNUM_OVERFLOW_P(i) \
  (((i) > 0 && (i) > MOST_POSITIVE_FIXNUM) \
   || ((i) < 0 && (i) < MOST_NEGATIVE_FIXNUM))

or:

#define FIXNUM_OVERFLOW_P(i) \
  !((i) <= MOST_POSITIVE_FIXNUM \
    && (i) >= MOST_NEGATIVE_FIXNUM)

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
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