Question

I am trying to interface some C/C++ code from C# via a dll. I am not a fluent C/C++ programmer but use C# all the time. I am attempting to deal with these C/C++ types at the moment:

#ifndef struct_emxArray_char_T_1024
#define struct_emxArray_char_T_1024
struct emxArray_char_T_1024
{
    char_T data[1024];
    int32_T size[1];
};

#ifndef typedef_e_struct_T
#define typedef_e_struct_T
typedef struct
{
    emxArray_char_T_1024 value1;
    real_T value2;
    uint32_T value3;
    boolean_T value4;
} e_struct_T;

They were created by a third party tool. My unsuccessful C/C++ attempt to initialize value1 is as follows:

static char_T test[5] = { 'h', 'e', 'l', 'l', 'o'};

emxArray_char_T_1024 x;
x.data = test;
x.size = 5;

e_struct_T Parameters;
Parameters.value1 = x;
Parameters.value2 = 50;
Parameters.value3 = 3;
Parameters.value4 = FALSE;

I would like to ultimately expose a C# interface which takes the values:

PerformCPlusPlusComputation(string value1, double value2, int value3, bool value)

which initializes e_struct_T in C/C++. Any feedback would be very much appreciated. Thanks!

Answer 1

The lines

x.data = test;
x.size = 5;

contains two errors: The first is that you can’t assign one array to another, not even if they were the same size. Use e.g. std::copy to copy from one to the other.

The other error is that the size member is an array as well, and you can’t assign a single value to an array. You have to assign to x.size[0].

---

Correct lines could look like this:

std::copy(std::begin(test), std::end(test), std::begin(x.data));
x.size[0] = sizeof(test);