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Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor?

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Am 03/29/2012 07:49 AM, schrieb Francois Grieu:
> I think that the preprocessor part of cross-compilers is allowed
> to use wider types than their target. 1U can be 64-bit as far
> as the preprocessor is concerned, even if UINT_MAX is 0xFFFF,
> right?
> 
> At least, I met preprocessors which perform all their arithmetic
> over 32 bits, even though the compiler does not. In these
> #if ( 256<<8 )         is taken
>  if ( 256<<8 )         is not taken
> and this is NOT a non-conformance AFAIK.

Since C99 the preprocessor arithmetic must be the one of {u}intmaxt_t
for the target platform. So your example is well possible.

The #-comparison is done in intmax_t and goes ok.

The other one is done with int. If int has only 16 bit 256<<8 is an
overflow and thus the behavior is undefined.

Jens

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what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? Francois Grieu <fgrieu@gmail.com> - 2012-03-28 22:34 +0200
  Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-28 14:47 -0700
    Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? Francois Grieu <fgrieu@gmail.com> - 2012-03-29 07:49 +0200
      Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-28 23:51 -0700
      Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? Jens Gustedt <jens.gustedt@loria.fr> - 2012-03-29 17:21 +0200
  Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? ImpalerCore <jadill33@gmail.com> - 2012-03-28 14:14 -0700
  Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? China Blue Water Navy <chine.bleu@yahoo.com> - 2012-04-02 15:04 -0700
    Re: what would be the most portable way to test if UINT_MAX>=0xFFFFFFF with the preprocessor? Francois Grieu <fgrieu@gmail.com> - 2012-04-03 18:15 +0200

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