Re: FreeVision port to GPC: helpers needed

10 Mar 2000

      Marco van de Voort wrote:
...
How does it work effectively? So something like:
procedure proc1(x:longint);
procedure proc2(x:longint);
begin
end;
begin
end;
type myproctype=procedure(x:longint);
procedure proc3(x:pointer);
begin
  myproctype(x);
end;
begin
 proc3(@proc1);
 proc3(@proc2);
end;
This does not work because
  1) `myproctype(x)' lacks an argument to the called procedure, and
  2) your "main program" does not know `proc2' which is local to `proc1'.

The following _does_ work:

  program foo;

  type myproctype=procedure(x:longint);

  procedure proc3(x:pointer);

  begin
    myproctype(x)(21);
  end;

  procedure proc1(x:longint);

  procedure proc2(y:longint);

  begin
    writeln(2*x)
  end;

  begin
    proc3(@proc2)
  end;

  begin
    proc3(@proc1)
  end.

GPC uses "trampolines" to pass the pointer of the local
procedure. (See `info -f jarg400 -n trampoline'.)

    Peter

-- 
http://home.pages.de/~Peter.Gerwinski/ - G-N-U GmbH: http://www.g-n-u.de
Maintainer GNU Pascal - http://home.pages.de/~GNU-Pascal/ - gpc-19990118
GnuPG key fingerprint: 9E7C 0FC4 8A62 5536 1730 A932 9834 65DB 2143 9422
keys: ftp://ftp.gerwinski.de/pub/keys/ - AntiSpam: http://spam.abuse.net

Re: FreeVision port to GPC: helpers needed

Peter Gerwinski