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Date: Sun, 02 Apr 2006 23:25:59 -0400
From: "Larry Hall (Cygwin)" <reply-to-list-only-lh AT cygwin DOT com>
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Subject: Re: Initialisation with data from dll-libraries
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Jørgen Steensgaard-Madsen wrote:
> Larry Hall (Cygwin <reply-to-list-only-lh <at> cygwin.com> writes:
> 
>> Jørgen Steensgaard-Madsen wrote:
>>> Asking for help.
>> You haven't said where the dispatch table is or how it is supposed to filled
>> in.  
> 
> First of all, thanks for reacting so promptly.
> 
> The dispatch table is an array of pointers in a C-program file to be linked
> against the libraries.  Initialised is expressed as a usual array declaration
> initialised with individual entries given as 
> 
>     &some_function
> 
> where some_function is declared as extern in the same file.  This methods works
> nicely with static linkage, and also with dynamic linkage on a Linux box.

Windows DLLs don't work the same as shared objects.  If you want to call
functions in a particular DLL, you can link your program against an import
library for the DLL which contains the functions you'll be using.  The import
library provides the stubs for the functions that allow your program to link.
At run-time, they ferry your calls across to the DLL implementation.  If you
don't want this, you can use dlopen and dlsym to programmatically load the
DLL with the functions you want to call and get the function pointers.  You
may be able to adapt the former approach to your existing code with few
changes.  If that sounds preferable to you, I suggest you read up on
Windows DLLs, importing/exporting functions, and import libraries.  If you'd
prefer the latter route, which is completely portable to Unix/Linux once
you've made the initial code changes, I'd recommend reading up on dlopen and
dlsym.  In either case, neither of these subjects is Cygwin-specific so
further discussion of these general areas are really off-topic for this list.


-- 
Larry Hall                              http://www.rfk.com
RFK Partners, Inc.                      (508) 893-9779 - RFK Office
838 Washington Street                   (508) 893-9889 - FAX
Holliston, MA 01746

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