minnlcstate state;

{
    std::vector<double> dataForC = ...;

    real_2d_array C;
    C.attach_to_ptr(dataForC, nRows, nCols);

    real_1d_aray CT = ...;

    minnlcsetlc(state, C, CT);
}

// At this point `dataForC` is no longer valid, and with it the pointer to which `C` was attached.
// Is it safe to delete data to which `C` was attached? I.e., does ALGLIB make a copy of object `C` that was passed to `minnlcsetlc`?
minnlcoptimize(state, ...);