Re: cpp problem found by imake

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, May 03, 2000 at 12:11:56AM -0700, Zack Weinberg wrote:
> On Tue, May 02, 2000 at 11:47:33PM -0700, Zack Weinberg wrote:
> > On Wed, May 03, 2000 at 08:02:37AM +0200, Jakub Jelinek wrote:
> > 
> > > #define Header /usr/include/stdio
> > > #define MakeHeader(x) "x.h"
> > > #define Include MakeHeader(x)
> > 			     ^ You meant Header, right?
> > > #include Include
> > 
> > This should work, but it segfaults.  I'll fix that shortly.
> 
> Correction: this should not work, and the segfault appears to be due
> to unrelated bustage in my work area.
> 
> cpplib, cccp (from 2.95), and SunOS 4 cpp all wind up with
> 
> #include "Header.h"
> 
> from the above example, with 'x' replaced by 'Header' in the #define
> Include line.  This is not a surprise: what happened was something
> like
> 
>  Include -> MakeHeader ( Header )
> 	 -> " Header .h"	// -traditional, so no extra whitespace...
> 	 -> "Header.h"		// a string, not subject to further expansion.
> 
> I could easily change this, but that wouldn't be the way a "real K+R
> preprocessor" behaves.  The conclusion is that there simply is no way
> to paste together an include name with -traditional on.
> 
> I'm going to have to ask you what X11 is _really_ trying to achieve
> here, because this seems utterly perverse, and I'll bet there's a
> simpler and more portable way.  I've got XFree 4.0 source lying
> around, but I can't find the place where it does this.

xc/config/cf/Imake.tmpl in my copy (have updated it from CVS to make sure it
hasn't been removed):
If TopLevelProject was always X11, this would be easily solveable, but one
can change it (and I think kerberos and similar beasts change it).
BTW: This is not new in XF4.0, it seems to be present e.g. in XF 3.3.6 as
well.

#ifndef TopLevelProject
# define TopLevelProject        X11
#endif
#ifndef ProjectRulesFile
# define ProjectRulesFile       Concat3(<,TopLevelProject,.rules>)
#endif
#include ProjectRulesFile
#ifndef LocalRulesFile
/* need this to make ANSI-style preprocessors happy */
#define LocalRulesFile <noop.rules>
#endif
#include LocalRulesFile

/*
 * get project-specific configuration and rules
 */
#ifndef ProjectTmplFile
#define ProjectTmplFile         Concat3(<,TopLevelProject,.tmpl>)
#endif
#include ProjectTmplFile
#ifndef LocalTmplFile
/* need this to make ANSI-style preprocessors happy */
#define LocalTmplFile <noop.rules>
#endif
#include LocalTmplFile

	Jakub