Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!brunix!sdm
From: sdm@cs.brown.edu (Scott Meyers)
Newsgroups: comp.lang.c++
Subject: Re: Mixing C and C++
Message-ID: <72158@brunix.UUCP>
Date: 15 Apr 91 16:51:54 GMT
References: <72092@brunix.UUCP> <670@taumet.com>
Sender: news@brunix.UUCP
Reply-To: sdm@cs.brown.edu (Scott Meyers)
Organization: Brown University Department of Computer Science
Lines: 38

In article <670@taumet.com> steve@taumet.com (Stephen Clamage) writes:
| What you describe is common in implementations of C++, but does not
| usually apply to C.  C++ allows specification of runtime code to
| be executed (conceptually) before main(), and (conceptually) after
| main() exits.  C provides no such facility to the C programmer, and
| it is unusual for a C compiler to require that main() be compiled by
| that C compiler (but some have that requirement for other reasons).
|
| Of the C++ object-code compilers I am familiar with, all provide a
| companion C compiler, and none have any requirement on main() that
| would prevent mixing C and C++ code.  Some C++ object-code compilers
| do not even require main() to be written in C++.
| 
| So: is your question theoretical, or do you actually have separate C and
| C++ compilers which each require main() to be compiled by that compiler?

My question is theoretical (i.e., I don't have a particular problem right
now), but of importance because of portability:  just because one or two
combinations of C and C++ work together, does that mean I can sleep soundly
at night before porting to a new platform with a new pair of compilers?

As an example, suppose I have the following in C:
    
    const x = 10;   /* global */
    int y = x + 1;  /* global */

A good C compiler will do the arithmetic at compile time, but I don't think
the language requires that.  If not, then sometime before main there has to
be the computation of x+1 to initialize y.  Or am I missing the point
entirely?

Thanks,

Scott


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