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Re: cpp replacement


On Tue, 2 March 1999, 00:43:30, law@hurl.cygnus.com wrote:

 > 
 >   In message <199902010324.WAA23294@blastula.phys.columbia.edu>you write:
 >   > On Sun, 31 Jan 1999 12:45:16 -0700, Jeffrey A Law wrote:
 >   > >
 >   > >When y'all have settled on the script, can you send a patch which includes
 >   >  the
 >   > >cpp script and the Makefile.in changes to get the script installed?
 >   > >
 >   > >We actually wanted to include this kind of script in egcs-1.1, but it fell
 >   > >through the cracks.
 >   > 
 >   > Here's my patch.  It should work correctly on all supported Unixes,
 >   > but I doubt it works on cygwin/mingwin/djgpp.  Shouldn't be too hard
 >   > to fix, just gotta find someone who knows how you get shell scripts to
 >   > be executable under DOS.
 >   > 
 >   > zw
 >   > 
 >   > 1999-01-31 22:22 -0500  Zack Weinberg  <zack@rabi.columbia.edu>
 >   > 
 >   > 	* cpp.in: New file.
 >   > 	* Makefile.in (install-driver): Also install cpp wrapper in
 >   > 	$(bindir). 
 >   > 	(xcpp): New target.
 > I think I like HJ's old cpp patch better.  It seems a lot more complete for
 > the kinds of problems we're trying to address.
 > 
 > Specifically it handles installing cpp in a second location, which helps with
 > the "/lib/cpp" problem (lots of stuff hard-codes /lib/cpp :(
 > 
 > It also handles install/uninstall better (we really ought to fix uninstall
 > one day, several folks have asked about it).
 > 
 > HJ's patch has got a few minor problems, but nothing I shouldn't be able
 > to resolve on the fly.
 > 
 > I do have one question, why does your patch bother with argument processing?
 > cpp's interface has always been:  cpp [switches] [infile] [outfile]
 > where infile and outfile default to stdin/stdout automatically.  Does gcc -E
 > not handle input on stdin or something like that?

IIRC, the whole thread started because "cpp" alone does no longer
define the same machine/os specific macros that "gcc -E" does; e.g.
"i386", desperately needed by "Imake", was missing.  So we decided
to use "gcc -E" instead.  This needs some tweaking due to the following:

 1. Running "gcc -E" with input from stdin gives:

      $ echo "abc" | gcc -E -Dabc=xyz
      gcc: No input files

    Appending a single "-" results in the exepted:

      # 1 ""
      xyz 

 2. When such a wrapper script would be used for preprocessing
    files with unknown extensions (e.g. the calendar application
    "plan" processes its "~/.holiday" file with "cpp"), this
    will result in annoying error message from the linker as in:

      $ gcc -E .holiday
      gcc: .holiday: linker input file unused since linking not done

    With '-x c' added, gcc will simply call "cccp" and then terminate
    instead of "passing the unknown file to ld".

 > 
 > Thanks,
 > jeff

I don't know exactly, how Zack's script looks like, but provided that
"cccp" and "gcc -E" don't necessarily define the same macros, the wrapper
script should consider the above two issues.

manfred


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