Date:	Tue, 20 Oct 1998 18:22:03 +0200 (IST)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender:	eliz AT is
To:	Primro <jiminy AT olag DOT com>
cc:	djgpp AT delorie DOT com
Subject:	Re: C++ versus C libs
In-Reply-To:	<362c9337.512419995@news.cis.yale.edu>
Message-ID:	<Pine.SUN.3.91.981020181546.19597D-100000@is>
MIME-Version:	1.0
Reply-To:	djgpp AT delorie DOT com

On Tue, 20 Oct 1998, Primro wrote:

> Well, I know I phrased that very badly (reflecting a shaky
> understanding of all this)... but what I was really asking was "where
> are the functions referenced in the header file coming from." That is,
> if I include stdio.h in a C++ file, do the functions I end up adding
> to my program come from the gpp lib, or the gcc lib (libc). I assume
> the gpp lib.

Your assumption is wrong.  The C++ libraries don't replace the standard C 
functions, they are in addition to them.  When you link a C++ program, 
gxx instructs the linker to scan the C++ libraries first, then the C 
library.  (Add -v to the gxx link command line, and you will see this 
yourself.)  So even if you link a C++ program, functions declared on 
stdio.h and other C headers come from the usual libc.a.

> And beneath that question, basically I am wondering if a C program can
> use functions from my C++ lib file, and vice-versa---> or are they
> somehow too different.

C++ functions can (and do) use functions from libc.a, that is why all 
prototypes in the C headers are declared inside ``extern "C"'' block, 
just like the one you missed.

But C programs cannot easily use C++ library functions since the actual 
name of the function visible to the linker is mangled to include some 
indication of its argument types (there can be several different C++ 
functions with the same name but different argument types--that's what 
polymorphism is all about).

> Thanks, Eli- your quick response means I might make some progress
> today.

You are welcome.

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