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Date: Tue, 17 Jan 2006 06:31:05 +0100
From: Peter Ekberg <peda AT lysator DOT liu DOT se>
To: cygwin AT cygwin DOT com
Subject: Re: ATT: gcc maintainer (was Re: cpp does not honor the -undef option.)
Message-ID: <20060117053105.GA25800@sellafield.lysator.liu.se>
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On Mon, Jan 16, 2006 at 10:49:38PM -0600, * * wrote:
> On 1/16/06, Peter Ekberg <peda AT lysator DOT liu DOT se> wrote:
> > On Mon, Jan 09, 2006 at 10:58:00AM +0100, Peter Ekberg wrote:
> > > Hello!
> > >
> > > I recently tried to build a package that was using cpp for other
> > > purposes than preprocessing C files. Its configure script was
> > > looking for a way to not have cpp predefine anything, and it
> > > specifically tried the -undef option, but failed. From reading the
> > > docs, I couldn't figure out why. Here's a quote from "info cpp":
> > >
> > > '-undef'
> > >      Do not predefine any system-specific or GCC-specific macros.  The
> > >      standard predefined macros remain defined.  *Note Standard
> > >      Predefined Macros::.
> 
> Apparently some macros must remain defined.  What macros specifically
> did you notice still defined that you would consider "system-specific"
> (i.e. __cygwin__ or __CYGWIN__ or CYGWIN) or "gcc-specific"?

Well, "cpp -undef -mD < /dev/null" gives me this list:

#define __unix 1
#define __STDC_HOSTED__ 1
#define __unix__ 1
#define unix 1
#define __CYGWIN__ 1
#define __CYGWIN32__ 1

I would consider all but __STDC_HOSTED__ system/gcc-specific. Which
should be apparent if you read the "*Note Standard Predefined Macros"
in the above quote, as that's the only define listed in the note.

In my specific case, the configure script is looking for a way to
not have "unix" defined.

FWIW, the provided patch fixes all of the above, so that the output
from the above command is:

#define __STDC_HOSTED__ 1

It seems I'm not the only one with this problem, even though cpp now
seems to be in better shape in this regard:
http://www.cygwin.com/ml/cygwin/2002-05/msg01613.html

Cheers,
Peter

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