Error using loadlibrary line 440

Hello. I am trying to connect an EPOS controller with Matlab through a .dll file. I use Matlab function loadlibrary('EposCmd64.dll','Definitions.h') and keep getting the same error

Error using loadlibrary (line 440)
Building EposCmd_thunk_pcwin64 failed.  Compiler output is:
cl -I"C:\Program Files\MATLAB\R2014b\extern\include"  /W3  /nologo  -I"C:\Program
Files\MATLAB\R2014b\extern\include" -I"C:\Program Files\MATLAB\R2014b\simulink\include"
/D_CRT_SECURE_NO_DEPRECATE /D_SCL_SECURE_NO_DEPRECATE /D_SECURE_SCL=0
-I"C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con"
-I"C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con" "EposCmd_thunk_pcwin64.c" -LD
-Fe"EposCmd_thunk_pcwin64.dll"
EposCmd_thunk_pcwin64.c
C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con\Definitions.h(121) : error C2059: syntax
error : 'string'

The last line keeps on repeating for the rest lines of 'Definitions.h' . I have searched and tried almost everything so far. I have the Microsoft Visual Studio C++ 2015 SDK so I believe I have all the necessary stuff. Also, I can't create MEX files because the functions are too many to create!

Thanks in advance, Konstantinos

[Walter Roberson]

Are you trying to use the C++ "string" datatype in the interface? Your .c file implies you are using C rather than C++, and you could have problems if you try to mix the two.

[Kons Tsak]

In the 'Definitions.h' header there is no use of the type "string". However it does occure an error. This is also something that puzzles me. I have done #include < string.h > but it didn't make any difference. I attach the header file. The problem occurs at function call

//Communication
    Initialisation_DllExport HANDLE __stdcall VCS_OpenDevice(char* DeviceName, char* ProtocolStackName, char* InterfaceName, char* PortName, DWORD* pErrorCode);

and keeps on going at almost every single line after that.

Thank you

Answer 1

[Kons Tsak]

Finally I found a correct .zip that worked fine. You can find it here http://www.mathworks.com/matlabcentral/fileexchange/53735-commanding-maxon-motors-epos2-motor-controller-from-matlab. I had already seen this one but hadn't undestand that I could actually download some file etc. Still new at Matlab. I also attach the correct 'Definitions.h' file for any future reference. In general, the "extern C" is not necessary here, in fact it does cause the loadlibrary to produce errors.

Answer 2

[Philip Borghesani]

The header file as written is not compatible with C code only c++. On first inspection It looks like the dll might be callable from c and usable with loadlibrary but the header will need to be fixed.

The basic problem is the definitions that look like:

     #define Initialisation_DllExport            extern "C" __declspec( dllexport )

and there use. The simplest fix to get loadlibrary working would be to remove all references to these defines from the code they are not needed for loadlibrary.

[Kons Tsak]

I commented out the #define lines as you suggested but I got some new errors like

Error using loadlibrary (line 440)
Building EposCmd64_thunk_pcwin64 failed.  Compiler output is:
cl -I"C:\Program Files\MATLAB\R2014b\extern\include"  /W3  /nologo  -I"C:\Program
Files\MATLAB\R2014b\extern\include" -I"C:\Program Files\MATLAB\R2014b\simulink\include"
/D_CRT_SECURE_NO_DEPRECATE /D_SCL_SECURE_NO_DEPRECATE /D_SECURE_SCL=0
-I"C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con"
-I"C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con" "EposCmd64_thunk_pcwin64.c" -LD
-Fe"EposCmd64_thunk_pcwin64.dll"
EposCmd64_thunk_pcwin64.c
C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con\Definitions.h(123) : error C2054: expected
'(' to follow 'Initialisation_DllExport'
C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con\Definitions.h(123) : error C2085:
'VCS_OpenDevice' : not in formal parameter list
C:\Users\Konstantinos\Desktop\Thesis\MAT_epos_con\Definitions.h(124) : error C2061: syntax
error : identifier 'Initialisation_DllExport'

The 3 types of error also continue for the next lined as well. Searching the web I have found similar cases. It seems I need to edit the header file so as to be C compatible for Matlab.

Thank you for your response. If you have any further suggestions I would be more than grateful.