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Re: null pointer constant, address constant

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James Kuyper <jameskuyper@verizon.net> wrote:
> On 12/18/2012 03:06 PM, Szabolcs Nagy wrote:
>> does not matter, your concerns only matter if the expression is
>> evaluated, but it is not:
>> 
>>  sizeof( *(0?(double*)0:(void*)((char*)1 - 1)) )
> 
> You didn't mention that in your original message.

sorry

> Can you give an example where it was reasonable, in a context where an
> ICE was required, to use an expression that pushed (or exceeded) the
> limits on what is permitted for an ICE?

it is required for an elaborate hack to workaround a
silliness of the standard that is tgmath.h

(ie. i have an implementation of tgmath.h which is
done with minimal compiler support using the typeof
extension present in many compilers)
(yes c11 _Generic could solve the issue but is not
practical as it is not supported on the compilers i
care about and i cannot modify the compilers, i'm
only implementing the standard library)

while testing the implementation it turned out that the
tested compilers disagreed about what is an ICE or a
null pointer constant (so it's not that trivial matter
after all)

eg on some compilers

 #define __is_integral(x) !((1?1:x)/2)
 __is_integral(1.0)

is an ICE and null pointer constant on others not

 0 ? (double*)0 : 0 ? (void*)0 : (void*)0

has type double* on some compilers on others void*

none of the tested compilers are completely standard
conformant (gcc, clang) which means i can implement
tgmath.h with typeof only, if they were conformant i
could not

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null pointer constant, address constant Szabolcs Nagy <nsz@port70.net> - 2012-12-18 13:25 +0000
  Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-18 09:53 -0500
    Re: null pointer constant, address constant Szabolcs Nagy <nsz@port70.net> - 2012-12-18 20:06 +0000
      Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-18 15:39 -0500
        Re: null pointer constant, address constant Szabolcs Nagy <nsz@port70.net> - 2012-12-19 00:44 +0000
          Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-18 20:24 -0500
            Re: null pointer constant, address constant Szabolcs Nagy <nsz@port70.net> - 2012-12-19 10:27 +0000
              Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-19 07:15 -0500
              Re: null pointer constant, address constant Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-12-21 03:03 +0200
                Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-21 12:13 -0500
                Re: null pointer constant, address constant Szabolcs Nagy <nsz@port70.net> - 2013-01-09 00:44 +0000
                Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2013-01-08 20:21 -0500
                Re: null pointer constant, address constant Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-01-08 20:46 -0500
          Re: null pointer constant, address constant Shao Miller <sha0.miller@gmail.com> - 2012-12-18 20:37 -0500
      Re: null pointer constant, address constant Shao Miller <sha0.miller@gmail.com> - 2012-12-18 16:15 -0500
        Re: null pointer constant, address constant Keith Thompson <kst-u@mib.org> - 2012-12-18 15:52 -0800
          Re: null pointer constant, address constant Shao Miller <sha0.miller@gmail.com> - 2012-12-18 19:12 -0500
            Re: null pointer constant, address constant Shao Miller <sha0.miller@gmail.com> - 2012-12-18 19:51 -0500
          Re: null pointer constant, address constant Keith Thompson <kst-u@mib.org> - 2012-12-18 17:02 -0800
          Re: null pointer constant, address constant "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2012-12-20 05:34 -0800
            Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-20 10:33 -0500
              Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-20 12:28 -0500
                Re: null pointer constant, address constant Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-20 21:13 -0800
              Re: null pointer constant, address constant Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-20 21:05 -0800
            Re: null pointer constant, address constant Shao Miller <sha0.miller@gmail.com> - 2012-12-20 12:17 -0500
            Re: null pointer constant, address constant Keith Thompson <kst-u@mib.org> - 2012-12-20 12:10 -0800
              Re: null pointer constant, address constant Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-20 21:25 -0800
  Re: null pointer constant, address constant Shao Miller <sha0.miller@gmail.com> - 2012-12-18 14:02 -0500
    Re: null pointer constant, address constant Szabolcs Nagy <nsz@port70.net> - 2012-12-18 20:09 +0000
      Re: null pointer constant, address constant James Kuyper <jameskuyper@verizon.net> - 2012-12-18 15:54 -0500
        Re: null pointer constant, address constant Shao Miller <sha0.miller@gmail.com> - 2012-12-18 16:18 -0500

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