RE: Xggi/glide

[Mumit Khan <khan@xraylith.wisc.EDU>]

On Wed, 14 Jul 1999, Suhaib M. Siddiqi wrote:

> 
> > >                  from cfbpntwin.c:64:
> > >
> > c:/cygnus/CYGWIN~4/H-I586~1/bin/../lib/gcc-lib/i586-cygwin32/egcs-
> > 2.91.66/..
> > > /../
> > > ../../i586-cygwin32/include/stdlib.h:46: parse error before `int'
> > > make[5]: *** [cfbpntwin.o] Error 1
> > >
> >
> > Line 46 declares a function named abs, and it might be that there is an
> > existing abs macro when the compiler sees it and croaks. It really is
> > useful to look at the preprocessed file and see what happens there after
> > pre-processing.
> >
> > Regards,
> > Mumit
> >
> >
> 
> Mumit,
> 
> Thanks.  Actually problem exsists in the recent snapshots too.  i tried a
> recent
> snap shot and in that case the number of line moved from 46 to 51.  If I
> compile with -O2 flag
> it works, but with -g flag it gives a parse error.  The code compiled with
> optimization
> after doing changes over the weekend, is doing core dumps.  I need to get
> everything compiled
> with -g so I can debug it.  I forwarding this message to list, perhaps
> someone else
> on Xfree project also may have notice this problem.
> 
> Attached is the --save-temps file and code.
> 

Suhaib,

Please follow my suggestion and take a look at the preprocessed file. The
problem is obvious. Some header file is defining a macro named abs(x), and 
it's being turned on or off depending on if -g or -Ox is used. See line 
15671 in the preprocessed file for details.

What is happening is the following:

- some header, say a.h, file is doing something like the following:
  
  #define abs(x) ((x) > 0 ? (x) : -(x))

- stdlib.h is declaring a library function, abs, as the following:
  
  int abs (int);

Now imagine the following sequence of includes:
  
  #include "a.h"
  #include <stdlib.h>

and now you see what will happen when the compiler sees the abs() prototype
in stdlib.h after encountering the macro in a.h.

Tracking it down should be pretty easy. Compile the file with -H, and
see what includes are coming in *before* stdlib.h. Grep for abs in those
files and you'll find the culprit. Another way to find it is to do the
following: add the following somewhere in your .c file:
  
  #define abs(x) (x)

and cpp will complain about duplicate abs macro and show you where the
previous definition was encountered.
  
Regards,
Mumit