Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cmcl2!rna!kc
From: kc@rna.UUCP (Kaare Christian)
Newsgroups: comp.lang.c++
Subject: Re: Zortech C++ vs Metagraphics Metawindow vs various linkers
Summary: C vs. C++ linkage, and outside libraries
Message-ID: <859@rna.UUCP>
Date: 28 Nov 89 16:14:31 GMT
References: <870@sys.uea.ac.uk> <24525@cup.portal.com>
Organization: Rockefeller University - Neurobiology
Lines: 28

In article <24525@cup.portal.com>, Nagle@cup.portal.com (John - Nagle) writes:
> 
>       I've recently upgraded to Zortech 2.0, and am trying to recompile a
> previously-working program that uses Metagraphics Metawindow.  The result
> is a finger-pointing exercise involving Zortech, Metagraphics, and Polytran.

I don't have a solution for this particular problem, but I would like
to throw in my two cents on the topic of using external libraries and
device drivers with ztc 2.0. I had a working 1.07 ztc program that
linked with an external library supplied by #9 computer (nnios). Their
library is just glue that hooks up to their device driver, which then
goes out to a special graphics board. Anyway, getting that previously
working setup to work with ztc 2.0 required:
	1. Fixing up the declarations and function prototypes. There was
a half day's work here, because the old declarations were sloppy, and not all
of the actual functions matched the prototypes exactly.
	2. Fixing up the linkage. This took a while to find.
The nnios library accesses their device driver via a far function
pointer, which is made to point at the driver entry point. The
device driver, originally written to work with C, does a far return and
follows ordinary C stack cleanup conventions.  Unfortunately the far
pointer's declaration was embedded in code using C++ linkage, hence ztc
was generating C++ style calls and cleanups. Anyway, switching the
pointer declaration to C linkage made everything work. This was unpleasant to
find because there aren't any error messages, and each trial lead to a
system crash.
Kaare Christian
kc@rna.rockefeller.edu