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Re: Evaluation of #elif - trying again

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on Fri Oct 14 2011, Edward Diener<eldiener-AT-tropicsoft.invalid> wrote:

> On 10/12/2011 12:34 PM, David Krauss wrote:
>>  On Sep 25, 8:26 am, Edward Diener<eldie...@tropicsoft.invalid>    wrote:
>
>>>
>>>    Having already asked for a clarification of the C standard in the
>>>    approprate NG I was told in no uncertain terms that the C standard is
>>>    not the source of the C++ standard on this issue. I am pursuing a change
>>>    on this issue in the C standard separately from my pursuit of this issue
>>>    in the C++ standard. But I have still received practically no response
>>>    regarding this issue in this NG regarding the interpretation in the C++
>>>    standard other than your reply above, which I appreciate. I still would
>>>    like some definite understanding how this is treated in C++ according to
>>>    the C++ standard.
>>>
>>>    So the question in my mind still remains: is an #elif expression
>>>    evaluated as a constant expression when its corresponding #if expression
>>>    is true ?
>>
>>  I stumbled on this recently, as I'm writing a C++ preprocessor. For
>>  curious other readers, the corresponding comp.std.c discussion
>>  concluded that this is also still a defect in C.
>>
>>  The problem is slightly broader than just expanding/interpreting
>>  constant expressions. Since skipped directives are only processed far
>>  enough to determine the nesting level, there is also the issue of
>>  preprocessing tokens following #else or #endif.
>>
>>  Since I read somewhere that some obsolete code allows an "argument" to
>>  #endif, I decided to ignore such a construction within a skipped group
>>  and flag it for a peer to an interpreted group. And, for what it's
>>  worth, I'm not evaluating the conditions of #elif directives following
>>  an interpreted #if or #elif group.
>
> Unforunately I could never get the C++ responders on this NG to take
> action for correcting the problem in C++. The best I was told was that I
> had to find someone who was a member of the C++ standards committee to
> take action for me and when I suggested to one responder, who may have
> been a member of the C++ standards committee, that I would gladly write
> up some form of document to get this corrected for C++, I received no
> further response.
>
> Both the C and C++ standard committees make it much too hard for a
> discerning C/C++ programmer to effect changes in the respective standards.

Have you tried posting a defect report here?  Presumably that should go
on the CWG issues list and at least get considered at the next meeting.

--
Dave Abrahams
BoostPro Computing
http://www.boostpro.com


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Evaluation of #elif - trying again Edward Diener<eldiener@tropicsoft.invalid> - 2011-09-11 09:13 -0700
  Re: Evaluation of #elif - trying again Marc <marc.glisse@gmail.com> - 2011-09-11 17:47 -0700
    Re: Evaluation of #elif - trying again Edward Diener<eldiener@tropicsoft.invalid> - 2011-09-25 08:26 -0700
      Re: Evaluation of #elif - trying again Marc<marc.glisse@gmail.com> - 2011-09-26 09:00 -0700
      Re: Evaluation of #elif - trying again David Krauss<potswa@gmail.com> - 2011-10-12 09:34 -0700
        Re: Evaluation of #elif - trying again Edward Diener<eldiener@tropicsoft.invalid> - 2011-10-13 22:42 -0700
          Re: Evaluation of #elif - trying again Francis Glassborow <francis.glassborow@btinternet.com> - 2011-10-14 12:02 -0700
          Re: Evaluation of #elif - trying again Dave Abrahams <dave@boostpro.com> - 2011-10-14 12:02 -0700
            Re: Evaluation of #elif - trying again Edward Diener<eldiener@tropicsoft.invalid> - 2011-10-15 09:30 -0700

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