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Re: Determining the 'type' of a variable, if only its name is given

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Hi

Am 23.06.2012 05:42, schrieb Tim Rentsch:
> Jens Gustedt <jens.gustedt@loria.fr> writes:
>
>> with C11's _Generic you may do that, provided your implementation
>> hasn't extended integer types that are narrower than int,
>>
>> you can do something horrible like
>>
>> _Generic(var,
>>         default: use_the_previous_method(var),
>>
>>         char:  (CHAR_MAX < UCHAR_MAX),
>>         char const:  (CHAR_MAX < UCHAR_MAX),
>>         [snip remainder]
> 
> In most cases I expect this approach will work fine, but unfortunately
> it doesn't always,

It did some more experiments with this and actually found that the
handling of qualified types is not very well designed with this new
_Generic tool. In the case it was asked here (for a variable, i.e an
lvalue) it seems consistent, but for rvalues it is completely
underspecified.

I'll post a question comp.std.c about this

> specifically for bitfields.

the signedness of bitfields is really a special case oddity. What
should _Generic trigger, here. The declared type or the effective
type?

A bitfield that is declared with just "int" could (implementation
defined) well be unsigned in nature. To the extreme on a system with
32 bit wide "int", a bit field with specification "int a:32" could be
unsigned.

> Btw, the many redundant parentheses are, well, redundant.

but not superficial

coding styles vary, as you probably know

Jens

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Thread

Determining the 'type' of a variable, if only its name is given John Reye <jononanon@googlemail.com> - 2012-06-15 01:47 -0700
  Re: Determining the 'type' of a variable, if only its name is given John Reye <jononanon@googlemail.com> - 2012-06-15 01:51 -0700
    Re: Determining the 'type' of a variable, if only its name is given James Kuyper <jameskuyper@verizon.net> - 2012-06-15 08:18 -0400
      Re: Determining the 'type' of a variable, if only its name is given "BartC" <bc@freeuk.com> - 2012-06-15 13:43 +0100
      Re: Determining the 'type' of a variable, if only its name is given Noob <root@127.0.0.1> - 2012-06-15 17:02 +0200
        Re: Determining the 'type' of a variable, if only its name is given Robert Miles <milesrf@Usenet-News.net> - 2012-07-23 23:20 -0500
    Re: Determining the 'type' of a variable, if only its name is given pete <pfiland@mindspring.com> - 2012-06-15 08:21 -0400
    Re: Determining the 'type' of a variable, if only its name is given Jens Gustedt <jens.gustedt@loria.fr> - 2012-06-15 16:37 +0200
      Re: Determining the 'type' of a variable, if only its name is given Ian Collins <ian-news@hotmail.com> - 2012-06-16 09:27 +1200
        Re: Determining the 'type' of a variable, if only its name is given Jens Gustedt <jens.gustedt@loria.fr> - 2012-06-16 09:38 +0200
      Re: Determining the 'type' of a variable, if only its name is given Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-22 20:42 -0700
        Re: Determining the 'type' of a variable, if only its name is given Jens Gustedt <jens.gustedt@loria.fr> - 2012-06-23 14:41 +0200
          Re: Determining the 'type' of a variable, if only its name is given Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-24 10:15 -0700
    Re: Determining the 'type' of a variable, if only its name is given Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-22 20:31 -0700

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