Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!taumet!steve
From: steve@taumet.com (Stephen Clamage)
Newsgroups: comp.lang.c++
Subject: Re: Mixing C with C++
Message-ID: <690@taumet.com>
Date: 24 Apr 91 15:51:57 GMT
References: <1991Apr22.064847.16929@cs.nott.ac.uk> <1991Apr23.133931.6716@ssd.kodak.com>
Organization: Taumetric Corporation, San Diego
Lines: 46

strollo@ssd.kodak.com (larry strollo ) writes:

>In article <1991Apr22.064847.16929@cs.nott.ac.uk> gas@cs.nott.ac.uk () writes:

>>> This is the easy bit.  The second step involves linking using C++ and
>>> not C.  Most of my replies pointed this out, but I had done this and
>>> still encountered problems (sorry for not pointing this out before).

>I'm confused.  Since the linker is just linking object files (generated from
>C I might add), what is special about the C++ "linker" ?

Usually linking is done via the cc or CC driver program (or whatever it is
called on your system).  The C++ version of the driver (or the driver
when told to operate in C++ mode) does different things for C++ than
for C.  If you know the ultimate linking command, you can use that
command directly, if less conveniently.  Sometimes the C++ driver runs
separate post-linking commands, which you would have to remember
to do as well.

>I'm working on a set of programs that are going to be implemented in C++,
>but must provide an interface callable from C.  It's probably not going to 
>be reasonable for me to insist that the user have Cfront.  Am I in trouble ? 

Not necessarily.  All C++ compilers I am familiar with require that
main() be compiled with with the C++ compiler.  This does not mean
that the user must have a C++ compiler to use your programs.

You write the actual main() in its own module like this:
	extern int my_main(int, char**);
	main(int argc, char** argv)
	{
	    return my_main(argc, argv);
	}
Compile it with the C++ compiler, and put it in your library.  Instruct
your users to write their main() with the name "my_main" instead.
Everything should just work.

In some cases, the user might want main() to take additional parameters,
one common variation being
	main(int argc, char** argv, char** environment)
You might have to provide several versions of main() in that case,
and at most one of them could be put into a library; the others
would have to be separate object files.
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com