[Swig-user] Fundamental DLL limitation

[Matthew B. <mat...@ea...>]

I've been a happy user of swig for a while.  However recently I've tried 
to use swig to interface a dll
to a convenient scripting language (I tried python and tcl.) and have 
run into problems.  The dll contains several functions that use the
standard call protocol and it also has an MS VC++ compatible library 
(.lib) stub.

The functions, however, were not generated from C or C++ code.  Let's 
say for example that I call the project
test and I have a few simple C style function prototypes in test.h.  The 
library we'll call lib.dll and lib.lib.  I create
an interface file test.i that simply includes test.h to create 
test_wrap.c.  Now how do I create the interface dll for say tcl?

One might naively try from the command line using MS VC++ 7.0 (actually 
the 2003 toolkit):

cl.exe $(TCL_Inc) /D__WIN32__ /LD test_wrap.c lib.lib 
$(TCL_libpath)\tcl84.lib  /link /OUT:test.dll

But this creates a dll with the symbols
Test_Init
Test_SafeInit

but does not contain any of the symbols in the original dll test.dll.  
When the dll is loaded into tcl, none of lib.dll's routines are visible.
(For the python case, the dll doesn't load at all.)   So it appears that 
one has to create a .def file and try to export the symbols to
test.dll.  Unfortunately in my case, test.dll has two symbols for each 
routine, a decorated and undecorated symbol.  This seems to cause 
link.exe to choke, when trying to create a new .dll.  What I really need 
is a way to append Test_Init and Test_SafeInit into the original (or a 
copied) lib.dll. 

This limitation appears to exist for most of the interfaces that rely on 
loading a dll.  Lua may be a little different since it builds a separate 
table with the external references, and I have gotten this to work in 
that case.  I really don't know what a clean solution to this is, but it 
certainly happens often enough (whenever there are libraries in dlls 
with no source code available), that there ought to be a nice way to do 
this.