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From: newsuser@LTH.Se (LTH network news server)
Newsgroups: comp.lang.c++
Subject: Re: C++ --> C
Summary: Translated C++ is not so portable
Message-ID: <1989Apr14.082659.19048@LTH.Se>
Date: 14 Apr 89 07:26:59 GMT
References: <173@cs.columbia.edu>
Reply-To: dag@Control.LTH.Se (Dag Bruck)
Organization: Dept. of Automatic Control, Lund Inst. of Technology, Sweden
Lines: 41

In article <173@cs.columbia.edu> jordan@cs.columbia.edu (Jordan Hayes) writes:
>Say you don't have a C++ compiler for a certain kind of machine,
>but you do have a C compiler.
>
>Say you've got a Sun somewhere on the same network.
>
>Can you get g++ or cfront to generate C on the Sun and have the
>unnamed machine compile that?

I think you would be heading for a lot of work:

   1.	There are some machine dependent parts in your compiler,
	e.g., sizes of basic data types, alignment, etc.

   2.	The C code will have all macros and inline functions expanded.
	As many machine dependent issues are described by macros in
	the system header files, you must make sure the C++ compiler
	on the development machine uses the header files of the target
	machine.

   3.	Debugging the C code produced by the C++ compiler is not funny.
	Can you be sure you got it right?  I am more willing to trust
	a ported compiler than a ported application.

   4.	Every change in the original C++ program (or even worse, a new
	release of system software on your target machine), requires you
	to port the application again. (It will of course be easier
	the n:th time.)

My view is that the C code produced by a C++ compiler is not particularly
portable, but I'm sure it can be, and has been, done.

Assuming the target machine is "similar" to your Sun, I would try porting
the compiler.  I think that is more cost-effective in the long run.

Dag Bruck
-- 
Department of Automatic Control		Internet:  dag@control.lth.se
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