From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Linking an object file in RHIDE/with GCC
Date: Sun, 29 Mar 1998 00:57:36 -0500
Organization: Two pounds of chaos and a pinch of salt.
Lines: 42
Message-ID: <351DE2D0.7600@cs.com>
References: <351d8edd DOT 107493 AT news DOT ziplink DOT net>
NNTP-Posting-Host: ppp245.cs.com
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

Jeff W./DMT wrote:
> 
> I have one example file that was written in C and came with
> instructions on how to compile it with the included object  file to
> produce an executable file.  That worked fine.  I wrote a very basic
> C++ file, and at the command line tried doing the same thing to link
> my program with the same object  file:
> gcc myfile.cc -O2 -o myfile.exe -lalleg objfile.o and for some reason
> gcc complains that it can't find the functions which are defined in
> the .O file.  

This is a well-known occurrence.  It happens because the C++ compiler
assumes that the functions which are declared in the header file are C++
functions, and therefore mangles their names according to the C++
name-mangling rules.  When it looks in the object file (a library is
merely a collection of object files), it doesn't find the proper mangled
names and so it complains.  The solution is simple - in the object
file's header file, wrap all the function declarations (and ideally the
entire header) with the following code:

#ifdef __cplusplus
extern "C" {
#endif

/* code */

#ifdef __cplusplus
}
#endif

That will cause the functions to be interpreted as C and the correct
names will be generated.

hth

-- 
---------------------------------------------------------------------
|      John M. Aldrich       | "Animals can be driven crazy by pla- |
|       aka Fighteer I       | cing too many in too small a pen.    |
|   mailto:fighteer AT cs DOT com   | Homo sapiens is the only animal that |
| http://www.cs.com/fighteer | voluntarily does this to himself."   |
---------------------------------------------------------------------