Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com
Date: Fri, 27 Aug 2004 14:28:00 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: Oliver <oliver DOT schoenborn AT utoronto DOT ca>
cc: cygwin AT cygwin DOT com
Subject: Re: questions about DLL's: .a, .def, and .dll
In-Reply-To: <loom.20040827T173827-426@post.gmane.org>
Message-ID: <Pine.GSO.4.61.0408271423560.6181@slinky.cs.nyu.edu>
References: <loom DOT 20040827T173827-426 AT post DOT gmane DOT org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Scanned-By: MIMEDefang 2.39

On Fri, 27 Aug 2004, Oliver wrote:

> Hi folks, I'm confused about the files that dllwrap
> creates. On Unix (where I've been programming forever) all you
> have to do is create a .so shared library. But dllwrap ends up
> creating a .a file, a .def file, and a .dll file, yet I can
> build a program that links to, e.g., mylib.dll, with only "-L. -lmylib",
> *wihtout* having the .def or .a available. So where and when are the .a and
> .def files needed?

The newer versions of gcc apparently allow you to link directly to a .dll
file.  The .def and .a are needed for older versions of gcc, and possibly
for some other tools.

> Also, I read in the various docs (dllhelpers etc) that you have to
> compile the file that has DllMain using either "extern 'C'" around the
> DllMain function, or make it a C file rather than a c++ file and compile
> with gcc, yet it worked for me as a c++ file without the extern, is this
> new behavior or is something going to blow up on me later?

The reason you want an 'extern "C"' for DLL functions in general is that
g++ and the Windows C++ compilers (notably VC++) use different name
munging schemes, so a DLL built with C++ symbols won't be usable from
other applications that try to call those functions.  The reason you want
it for DllMain is that the Windows loader will be looking for the unmunged
name "DllMain".  Are you sure that it's really invoked when the DLL is
loaded?
	Igor
-- 
				http://cs.nyu.edu/~pechtcha/
      |\      _,,,---,,_		pechtcha AT cs DOT nyu DOT edu
ZZZzz /,`.-'`'    -.  ;-;;,_		igor AT watson DOT ibm DOT com
     |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski, Ph.D.
    '---''(_/--'  `-'\_) fL	a.k.a JaguaR-R-R-r-r-r-.-.-.  Meow!

"Happiness lies in being privileged to work hard for long hours in doing
whatever you think is worth doing."  -- Dr. Jubal Harshaw

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/