MATLAB Answers

Call .dll into MATLAB function/code and simulink

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Robert Evans
Robert Evans on 1 Aug 2017
Commented: Robert Evans on 2 Aug 2017
I am trying to access dynamic libraries inside of matlab that were written through Microsoft Visual Studio and cannot understand how to use the load library functions in order to do so. I have tried making a basic code in Microsoft and call it in MATLAB, but it inst working and is giving me errors all over. My Microsoft visual code looks like this:
// MathLibrary.h - Contains declaration of Function class #pragma once
#ifdef MATHLIBRARY_EXPORTS #define MATHLIBRARY_API __declspec(dllexport) #else #define MATHLIBRARY_API __declspec(dllimport) #endif
namespace MathLibrary { // This class is exported from the MathLibrary.dll class Functions { public: // Returns a + b static MATHLIBRARY_API double Add(double a, double b);
// Returns a * b static MATHLIBRARY_API double Multiply(double a, double b);
// Returns a + (a * b) static MATHLIBRARY_API double AddMultiply(double a, double b); }; }
Whenever I try to call this into matlab I end up receiving these errors:
_Warning: Message from C preprocessor: C:\Users\revans\Documents\Visual Studio 2017\Projects\MathLibraryAndClient\MathLibrary\MathLibrary.h:2:9: warning: #pragma once in main file #pragma once ^
> In loadlibrary In test1 (line 4) Error using loadlibrary Building libmx_thunk_pcwin64 failed. Compiler output is: C:\ProgramData\MATLAB\SupportPackages\R2017a\3P.instrset\mingw_492.instrset\bin\gcc -I"C:\Program Files\MATLAB\R2017a\extern\include" -fexceptions -fno-omit-frame-pointer -I"C:\Users\revans\Documents\Visual Studio 2017\Projects" -I"C:\Users\revans\Documents\Visual Studio 2017\Projects\MathLibraryAndClient\MathLibrary" "libmx_thunk_pcwin64.c" -o "libmx_thunk_pcwin64.dll" -shared In file included from libmx_thunk_pcwin64.c:27:0: C:\Users\revans\Documents\Visual Studio 2017\Projects\MathLibraryAndClient\MathLibrary/MathLibrary.h:10:1: error: unknown type name 'namespace' namespace MathLibrary ^ C:\Users\revans\Documents\Visual Studio 2017\Projects\MathLibraryAndClient\MathLibrary/MathLibrary.h:11:1: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token { ^
Error in test1 (line 4) loadlibrary('libmx',hfile)_


Rik on 1 Aug 2017
As far as I understand, there is no longer a support for dll files in Matlab, however, you can compile your c/c++/fortran into a mex file for use in Matlab.
Philip Borghesani
Philip Borghesani on 2 Aug 2017
DLLs are most definitely still supported by current versions of MATLAB that is not the issue here.

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Answers (1)

Philip Borghesani
Philip Borghesani on 2 Aug 2017
Your header file contains c++ code (namespaces for one). Loadlibrary has never supported c++ code in headers. You are free to use c++ in the implementation however the header must compile when included into a .c main program.
The best way to enforce this is to write a test program for your library in C. This also makes debugging the library much simpler and quicker then debugging the MATLAB process.

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Robert Evans
Robert Evans on 2 Aug 2017
Is there any way to convert the C++ code to be called into the matlab function? I have a previously constructed simulink and matlab function code that I am not skilled enough to put all into C.

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