Prevent memory leak when returning from MEX

Dear all,

I have the following code in a C file (using the MEX Gateway):

double *result;
Sim simulation(prhs, nrhs);
simulation.run(result);
...
plhs[0] = mxCreateDoubleMatrix(100, 2, mxREAL);
std::memcpy(mxGetPr(plhs[0]), result, 2 * 100 * sizeof(double));

variable 'result' contains the adress of another double* that contains a 2D array with all results, ie:

void Sim::run(double *(&res)) {
time_N = (double *) malloc(2 * 100 * sizeof(double));
...
res = time_N; //assign result to output.
}

and the array time_N is freed in the distructor of Sim:

Sim::~Sim()
{
    free(time_N);       //output vector.
}

Then I copy result into plhs[0]. This code compile and works perfectly, but I assume there is a memory leak somewhere because 'result' is not freed anywhere and the memory is dumped to plhs. Is that correct? How to overcome this issue?