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From: grp@Unify.com (Greg Pasquariello)
Newsgroups: comp.lang.c++
Subject: Re: bug with making C++ functions have C linkage ?
Message-ID: <1991Apr19.133158@Unify.com>
Date: 19 Apr 91 20:31:58 GMT
References: <1991Apr16.122905.23613@cs.nott.ac.uk>
Sender: news@Unify.Com (news admin)
Reply-To: grp@Unify.com (Greg Pasquariello)
Organization: Unify Corporation, Sacramento, CA, USA
Lines: 68

In article <1991Apr16.122905.23613@cs.nott.ac.uk>, gas@cs.nott.ac.uk (Alan
Shepherd) writes:
> 
> From my understanding, the correct way to make C++ functions
> accessible from modules compiled with c is to delcare them extern "C"
> as in the following example:
> 
> #include <stream.h>
> 
> extern "C" void tryCout();
> 
> void tryCout()
> {
>     cout << "Hello World\n";
> }
> 
> Now this can be called from a program compiled with cc.  For example,
> the following program:
> 
> extern void tryCout();
> 
> main()
> {
>     tryCout();
> }
> 
> This happily compiles without any warnings.  However, when running, a
> segv occurs in the cout operation.  This segv disappears if both
> modules are compiled with CC instead of just the first.  Adding
> another level of indirection to the code by writing another function
> to call tryCout doesn't work either.
> 
> Is this a bug ?  It certainly looks like it !
     
You need to declare, in your C++ source code, an object of class
Iostream_init.  The constructor for the class will initialize cin, cout,
cerr, and clog, and your core dump will go away.  Note that this relies on
C++ 2.0 and the iostreams package.

To try it out, do:

#include <iostream.h>
 
extern "C" void tryCout();

void tryCout()
{
     Iostream_init  io;
     cout << "Hello World\n";
}


On the C side:

extern void tryCout();

main()
{
    tryCout();
}
 
> Alan Shepherd

--

---
Greg Pasquariello	grp@unify.com
Unify Corporation 	Be good and never poison people