How to call a DLL with a char or a uint8_t

Question

Good afternoon,
I need to pass an array (image) to my dll.
I was able to successfully do this using 
imageProcess(int **a, ... ){;}
function declaration and using a signed or unsigned 32 bit integer as data type in labview DLL call
However, when I changed my function to either
imageProcess(char **a, ... ){;}     or       
imageProcess(uint8_t **a, ... ){;}
And when  I set the Labview Dll Call data type to    unsigned 8 bit integer
I get a Broken Arrow
With error: The function name specified for this node cannot be found in the library. Right-click the Call Library Function node and select Configure, then choose the correct function name.
I am also using IMAQ ImageToArray to obtain my array and using the ImagePixels(U8) output
Thank you,

Answer 1

Another possibility to make functions be unmangled is declaring them as extern "C" like this:
for a single function.
#define LibFunction __declspec(dllexport)
extern "C" MgErr LibFunction MyFunction(uInt8 *);
or:
#define LibFunction __declspec(dllexport)
#if defined(__cplusplus) || defined(__cplusplus__)
  extern "C" {
#endif
LibFunction MgErr MyFunction1(void);
LibFunction MgErr MyFunction2(uInt32);
#if defined(__cplusplus) || defined(__cplusplus__)
#endif
for multiple function prototypes.
This will tell the compiler to not mangle the names if it is invoked on a cpp file. And the LibFunction declaration is to declare the function as exported to the compiler, saving you to have to provide a DEF file for that purpuse. Remember that other compilers and platforms might and often do use a different syntax for the export declaration.
And alternative could be:
#define LibFunction(retval) extern "C" retval __declspec(dllexport)
LibFunction(MgErr) MyFunction(uInt8 *);
Also before claiming that there is a huge bug in LabVIEW that needs fixing you should make sure that you understand all in and outs of your C compiler toolchain. Something I wouldn't dare to claim to do!
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions