C Header Files -> Pascal_(re)

Mon, 31 Mar 1997 23:38:13 +0200 (MET DST)

According to Sven Engelhardt:
> I agree. Though IMHO there already exist such tools. Possibly
> I will do this ... (if there aren't any parser-specialist)

I don't know any parser-specialist.  (No, I am not one either.;)  I also
have never seen any working converter.  It would be highly welcome if
you would write one!

> Or may be there is a way to use C .h files directly by slightly
> modifiying the preprocessor. This would be a really great deal
> for guys like me that permanently update some library-version...

This would mean nothing else than to build the converter program into
GPC - making GPC understand C source in effect.  I don't think this is
a good idea.  The only reasonable thing I can imagine in this context
would be to write a preprocessor switch which changes the language during
the compilation, e.g.


    Program FooBar;

    Var
      Foo: Integer;

    #language C

    int bar;

    void setbar (void)
    {
      bar = foo;
    }
    
    #language Pascal

    begin
      Foo:= 3;
      SetBar;
    end.


or, when the C part is in a header file,


    Program FooBar;

    Var
      Foo: Integer;

    #language C
    #include "bar.h"
    #language Pascal

    begin
      Foo:= 3;
      SetBar;
    end.


... but such a thing would be *very* hard to write.  If you really
must rely on C headers which change from time to time, it is probably
the most reasonable thing to write a C module which uses the header
files and exports some well-defined functions.  Then you can write a
Unit which imports these functions as `external' functions and makes
them accessible for your Pascal program.

Another thing I did experiments with was a C program which includes
the header files and writes out Pascal source for all constants
defined in the header.

But all these are kludges.  The best thing still will be a converter
program.  What about writing it with GNU Pascal, so we will get a
real-world demo program simultaneously?

Happy hacking,

    Peter

  Dipl.-Phys. Peter Gerwinski, Essen, Germany, free physicist and programmer
peter.gerwinski@uni-essen.de - http://home.pages.de/~peter.gerwinski/ [970201]
       maintainer GNU Pascal - http://home.pages.de/~gnu-pascal/ [970125]

Peter Gerwinski (peter@agnes.dida.physik.uni-essen.de)