Using mingw to make a .dll for use in labview ?

Question

I have seen some posts on this, but none of them take it all the way from C code to configuring the shared library node...
My code is heavily based on this:
http://forums.ni.com/ni/board/message?board.id=170&thread.id=171056
Here are my files:
//reedll.h
#ifdef BUILD_DLL
// the dll exports
#define EXPORT __declspec(dllexport)
#else
// the exe imports
#define EXPORT __declspec(dllimport)
#endif
// function to be imported/exported
EXPORT void tstfunc(int A, int B, int C);
and:
//DLL_Test.c
#include "reedll.h"
EXPORT void tstfunc(int A, int B, int C)
  C = A + B;
Its meant to be as bare bones as I can get it. No crazy pointers or anything.
I compile as follows usin MinGW:
g++ -c -DBUILD_DLL DLL_Test.c
g++ -shared -o tst.dll -Wl,--out-implib,libtstdll.a DLL_Test.o
And it appears to compile fine.
When I go to import the .dll into the shared library node the "Function Name" field is garbled and says "Z7tstfunciii" instead of "tstfunc".  Needless to say the shared library function icon that results doesnt work

Answer 1

You should tell the mingw compiler to not name mangle the symbols. Most likely you use a cpp file enxtension and then mingw as Visual C will invoke the cpp compiler instead of c which by default name mangles function names.
If you want or need to use cpp, you can also try to declare your exported symbols like this:
#ifdef __cplusplus
extern "C" {
#endif
EXPORT void tstfunc(int A, int B, int C);
/* all the other function prototypes you do not want to be mangled */
#ifdef __cplusplus
#endif
Not sure if __cplusplus is defined by mingw, if not you have to find how it indicates that C++ mode has been invoked.
Message Edited by rolfk on 03-24-2010 02:48 PM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions