Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!uw-entropy!dataio!bright
From: bright@Data-IO.COM (Walter Bright)
Newsgroups: comp.lang.c++
Subject: Re: Using C++ AND C together
Message-ID: <2128@dataio.Data-IO.COM>
Date: 15 Sep 89 17:55:46 GMT
References: <953@ncratl.Atlanta.NCR.COM> <6590251@hplsla.HP.COM> <6497@columbia.edu>
Reply-To: bright@dataio.Data-IO.COM (Walter Bright)
Organization: Data I/O Corporation; Redmond, WA
Lines: 28

In article <6497@columbia.edu> kearns@cs.columbia.edu writes:
<Is it possible to link a C program with a C++ library?  
<The only a priori problem I could see is that the c++ global
<constructors would not be properly inited.  

Other problems:
1. C++ function names will appear bizarre to a C program.
2. The C compiler may not support the C++ calling sequence.

<I would like to create a library that supports C users, but I would
<prefer to write it in C++.  Yes? No? 

The best way is to enclose each C++ function that is to be callable from
C with a C 'wrapper', as in:

	static int function(int a, double b)
	{	// do C++ stuff
	}

	extern "C" int function_wrapper(int a, double b)
	{
		return function(a,b);
	}

(This is the 2.0 way of doing things.)

As far as how to call static constructors, that will vary from system
to system, and so will require customization for each.