Question

Am using calllib to access an external DLL from matlab. The DLL has a function in it, with a signature that looks like:

typedef struct resultStruct {
    double E;
    double W;
    double N; 
    double S;
    double Z;
    double Y;
} RESULT_STRUCT;


typedef struct inputStruct {
    double A;  
    double B; 
    double C; 
} INPUT_STRUCT;

RESULT_STRUCT calc(
    const INPUT_STRUCT* input);

When I try to invoke this in matlab,

loadlibrary('calc.dll','calc.h');
input.A = 1;
input.B = 2;
input.C = 3;

[res, st] = calllib('calc','calc',input);

I get the error:

??? Error using ==> calllib
The function return type is not supported.

Surprisingly, google shows up no hits on that error message, and there is nothing in the documentation for calllib: http://www.mathworks.com/help/techdoc/ref/calllib.html

My guess, is that since the function is returning a structure, matlab is puking. But there’s nothing in the documentation to suggest that. Although, none of the examples matlab provides, includes a structure as an output variable.

Answer 1

I suspect the same as you, namely that MATLAB doesn’t like a struct return type. Try returning a simple type and see if that works. Then I suggest contacting the excellent MATLAB support people.