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Subject: help with dynamic linkage?
From: skaller <skaller AT users DOT sourceforge DOT net>
To: cygwin AT cygwin DOT com
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Date: Sat, 11 Feb 2006 16:11:50 +1100
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hi, I'm having some problem getting dynamic linkage to work.
The linkage model is like this:

mainline <----- load time ---- librtl.dll
^                               / 
 \                             /
dlopen                        /
   \                         /
  user.dll <-----------------

gdb indicates the code is crashing in dlopen. LoadLibrary
doesn't appear to work either :)

All the code is C++. It works on Linux, it works with 
the option -mnocygwin, and it works with MSVC++.

It *used* to work with Cygwin. The problem is almost
certainly just using the wrong linker switches.

The linkage technique is to follow Linux: no export libraries
are built, build time linkage is done directly against the
dll. This works fine for a simple C program.

In order to build according to the above model,
there are 3 compilation steps, and 3 linkage steps.
However, the crash is unrelated to building the user.dll,
since it occurs whenever mainline calls dlopen, even with
a garbage name.

I have cygwin installed on 2 comps and get the same result.

I have tried two methods: generate and link against export file
librtl.dll.a, and just linkagainst librtl.dll. Both methods
fail. Warnings like:

Info: resolving vtable for XXXby linking to __imp__XXX (auto-import)

occur when linking the executable.

Switches: -O3 -fomit-frame-pointer --inline 

Hosts: 
* AMD64 running XP pro SP1
* AMD64x2 running XP64

Cygwin: latest setup provides.

Any hints what is causing the problem or how to fix it?

-- 
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net


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