From: khan AT xraylith DOT wisc DOT edu (Mumit Khan)
Subject: Re: Creation of dynamic object
7 Nov 1998 13:31:53 -0800
Message-ID: <9811070434.AA10400.cygnus.gnu-win32@modi.xraylith.wisc.edu>
References: <3641B49C DOT EF2B1045 AT uz DOT kuleuven DOT ac DOT be>
To: Jorrit Tyberghein <Jorrit DOT Tyberghein AT uz DOT kuleuven DOT ac DOT be>
Cc: gnu-win32 AT cygnus DOT com

Jorrit Tyberghein <Jorrit DOT Tyberghein AT uz DOT kuleuven DOT ac DOT be> writes:
> 
> I'm using the new CygWin B20 and try to create a dynamic object (not a DLL)
> which I can access from another executable with dlopen and dlsym.
> 
> On Unix I would create this (linking stage) with:
> 
> g++    -Wl -shared -o dynobj.so  obj_file1.o obj_file2.o obj_file3.o ... -l..

(1) Cygwin ld does not yet support the -shared flag.
(2) The correct form of passing flags to the linker is -Wl,-shared OR
    -Xlinker -shared (my preference because it's more consistent and 
    leads to fewer surprise). Your case works only because GCC "knows" 
    how to pass the -shared option through.
> 
> How can I fix this?  Note that I DON'T want to make a DLL.
> 

I honestly don't know the difference between a dynamic object and a DLL 
in this case, so I'll just offer my simple example. Visit
  
  ftp://ftp.xraylith.wisc.edu/pub/khan/gnu-win32/cygb20/misc/

and grab dlopen-example.tar.gz. It's as easy as building on any Unix
system. When ld is rewritten to accept -shared option, you can just
replace "dllwrap" with "ld" in the Makefile.

There seems to be one gotcha that I found while porting our loadable
simulation modules -- I have to use .dll extension, rather than our
usual .so extension. Must be missing something simple.

What exactly is the difference between a dynamic object and DLL?

Regards,
Mumit

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