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From:	"Alex Vinokur" <alexvn AT connect DOT to>
Subject:	Re: gcc -dM -E -xc /dev/null & g++ -dM -E -xc /dev/null
Date:	Tue, 14 Oct 2003 06:38:21 +0200
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"Ross Smith" <rosss AT pharos DOT co DOT nz> wrote in message news:bmf1m5$hsj$1 AT sea DOT gmane DOT org...
> Rick Rankin wrote:
> > --- Christopher Faylor <cgf-rcm AT cygwin DOT com> wrote:
> >
> >>On Mon, Oct 13, 2003 at 07:22:28AM +0200, Alex Vinokur wrote:
> >>
> >>>gcc -dM -E -xc /dev/null
> >>> and
> >>>g++ -dM -E -xc /dev/null
> >>> produce the same output.
> >>>
> >>>Is this a feature or a bug?
> >>
> >>It is not a bug.  Try it on linux.
> >>
> >>
> >>>How can one know that g++ (not gcc) is invoked?
> >>
> >>Isn't the __cplusplus define a feature of c++?  I'm too lazy to check if this
> >>is a g++ extension but I'd be surprised if it was.
> >
> > Yes, it's defined in section 16.8 (Predefined macro names) of the ANSI/ISO
> > standard.
>
> The original poster was using the -xc flag, which tells the compiler
> that the following source file is to be read as C regardless of the
> file name. I'd expect exactly the same preprocessor output from both
> frontends in that case.
>
[snip]

Thanks.

Now it seems to be OK.

$ g++ -dM -E -xc /dev/null > out_c

$ g++ -dM -E -xc++ /dev/null > out_c++

$ diff out_c out_c++
$ diff out_c out_c++
28a29
> #define __EXCEPTIONS 1
30a32
> #define __GXX_WEAK__ 1
43a46
> #define __WCHAR_UNSIGNED__ 1
50a54
> #define __cplusplus 1
51a56
> #define __DEPRECATED 1
53a59
> #define __GNUG__ 3


 =====================================
   Alex Vinokur
     mailto:alexvn AT connect DOT to
     http://mathforum.org/library/view/10978.html
     news://news.gmane.org/gmane.comp.lang.c++.perfometer
   =====================================





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