Question about mexfunction link to dll

Hello there，

Does anyone have idea about how to link dll or lib in the Mex command?

I have a C code link a external function from GHXDLL.dll and GHXDLL.lib. I defined the external function in header that the same one i used to generate the dll and lib.

typedef struct GHX{
  double output[28];
  int val;
}GHX;

#ifdef __cplusplus
extern "C" {  // only need to export C interface if
  // used by C++ source code
#endif

#ifdef GHXDLL_EXPORTS
#define MATHFUNCSDLL_API __declspec(dllexport) 
#else
#define MATHFUNCSDLL_API __declspec(dllimport) 
#endif

  MATHFUNCSDLL_API void GHXfunction(double *XIN, double *parameter, int mode, int hour, GHX *result);

#ifdef __cplusplus
}
#endif

I wrote a test code to call this function with linking to the lib and dll, and it works. Meanwhile, I wrote a simple test code for the Mex API, then I compile it from command line by

mex test.c,

and it works.

Then, I met problem. When I add the external function to the Mex API and compile in matlab with the following command, it fails.

    mex -largeArrayDims -I'c:\Users\zzhang\API' -L'c:\Users\zzhang\API'  -lGHXDLL  GHXCmexAPI.c

The errors are:

Error using mex
   Creating library GHXCmexAPI.lib and object GHXCmexAPI.exp
GHXCmexAPI.obj : error LNK2019: unresolved external symbol __imp_GHXfunction referenced in function mexFunction
GHXCmexAPI.mexw64 : fatal error LNK1120: 1 unresolved externals

I know this error means the mexfunction did not link to the lib with external function, but i have tried many different ways, and still cannot deal with it.

I hope someone can help me figure out how to mex it.

Thanks.

Zhicheng

Answer 1

[James Tursa]

I usually explicitly put the name of the lib file directly on the mex command. E.g., try something like this assuming the lib file is in the current directory with the c file:

mex -largeArrayDims -I'c:\Users\zzhang\API' -L'c:\Users\zzhang\API' GHXCmexAPI.c GHXDLL.lib

[Zhicheng Zhang]

James, Thanks. But it did not work.

[James Tursa]

Same error message or a different one? I would have expected that by explicitly including the GHXDLL.lib filename on the mex command line the linker would be able to find the function in the lib. Maybe it isn't being exported. Did you define the GHXDLL_EXPORTS macro anywhere in your code to force the export when you built the library?

[Zhicheng Zhang]

Same error. But i have figured out the problem. The reason is the dll version. I used to compile it in x32. Since I upgrade my matlab from R2012b to R2014a, it requires x64 version instead of x32. So i rebuilt the dll under x64 platform, then it works. Thanks.