Hi
I asked this question some days ago, but it never appeared in the
newsgoup.

Does anybody know if __cplusplus is standard #define for C++?

Dear moderator:
If you regected my post, do you know the answer?

--
rado
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[ moderator's note: The question as posed would not have been rejected,
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rado42 <rado42@my-deja.com> writes:

>Does anybody know if __cplusplus is standard #define for C++?

Yes. Every C++ compiler since about 1991 has defined __cplusplus
as a macro.

A standard-conforming compiler is required to define it to
the value 199711. The mysterious number is the date the
standard was voted out of committee: November 1997.

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Steve Clamage, stephen.clamage@sun.com
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rado42 <rado42@my-deja.com> wrote:

> Does anybody know if __cplusplus is standard #define for C++?

Yes. It is. The standard requires it; this is found in paragraph 16.8/1.

    -- Darin
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> >And a standard way for compiler vendors to identify themselves and their
> >compiler version?
>
> Compilers already have ways of doing that.
>
> >#elif __compiler == __gnu
>
> Why would that be any better than
>
>  #elif __GNUC__
>
> ?

Because none of the vendors can make up their minds how they want to do it.

#if defined(_MSC_VER)
  //
#elif defined(__BORLANDC__)
  //
#elif defined(__WATCOM_CPLUSPLUS__)
  //
#elif defined(__GNUC__)
  //
#endif

as you can see there are several ways for them to do it, and of course they
will.

This still leaves us with the problem of determining compiler version.
Admittedly the compiler versions themselves are going to vary wildly.

The POINT is that there should be a STANDARD way to determine these things.
 This is a STANDARD right?
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> C++ compilers use to #define __cplusplus which can be used by source code
> to check whether a C or C++ compiler is in use. Will that be part of the
> C++ standard?
>
>  [Yes.  See 16.8[cpp.predefined]/1 in the draft working paper.
>    -moderator (fjh).]

What about draft/standard revision identification?

#if __cplusplus >= 19970211  //Feb '97 standard or later?
#endif

And a standard way for compiler vendors to identify themselves and their
compiler version?

#if   __compiler == __msvc
#elif __compiler == __borland
#elif __compiler == __watcom
#elif __compiler == __gnu
#endif
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"Sean L. Palmer" <seanpalmer@mindspring.com> writes:

>> C++ compilers use to #define __cplusplus which can be used by source code
>> to check whether a C or C++ compiler is in use. Will that be part of the
>> C++ standard?
>>
>>  [Yes.  See 16.8[cpp.predefined]/1 in the draft working paper.
>>    -moderator (fjh).]
>
>What about draft/standard revision identification?
>
>#if __cplusplus >= 19970211  //Feb '97 standard or later?
>#endif

See 16.8[cpp.predefined]/1!
If you read that, you will see that the Feb 97 draft requires
that __cplusplus be defined as `199711L'.  So you should use

 #if __cplusplus >= 199711  //Feb '97 standard or later?
 ...
 #endif

>And a standard way for compiler vendors to identify themselves and their
>compiler version?

Compilers already have ways of doing that.

>#elif __compiler == __gnu

Why would that be any better than

 #elif __GNUC__

?

--
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WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh@128.250.37.3         |     -- the last words of T. S. Garp.
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Fergus Henderson wrote:
>
> See 16.8[cpp.predefined]/1!
> If you read that, you will see that the Feb 97 draft requires
> that __cplusplus be defined as `199711L'.  So you should use
>
>         #if __cplusplus >= 199711  //Feb '97 standard or later?
>         ...
>         #endif

The draft is dated 2-Dec-96, and was presumably written in November.
Would I be right in guessing that the "199711L" in the draft is a typo,
and it's meant to be "199611L"?

--
Ross Smith .................................... Wellington, New Zealand
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     person would be interested in."          -- Ashleigh Brilliant
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Ross Smith <ross.smith@nz.eds.com> writes:

> Fergus Henderson wrote:
> >
> > See 16.8[cpp.predefined]/1!
> > If you read that, you will see that the Feb 97 draft requires
> > that __cplusplus be defined as `199711L'.  So you should use
> >
> >         #if __cplusplus >= 199711  //Feb '97 standard or later?
> >         ...
> >         #endif
>
> The draft is dated 2-Dec-96, and was presumably written in November.
> Would I be right in guessing that the "199711L" in the draft is a typo,
> and it's meant to be "199611L"?

No.  That value is supposed to be the date when the C++ standard
becomes final.  It has always been understood that the number in the
draft is basically a placeholder: the project editor will replace it
with the appropriate date when the time comes.
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C++ compilers use to #define __cplusplus which can be used by source code
to check whether a C or C++ compiler is in use. Will that be part of the
C++ standard?

 [Yes.  See 16.8[cpp.predefined]/1 in the draft working paper.
   -moderator (fjh).]

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