Question

I ve got a problem with allocating cli::array in function.

I have this kind of object:

array<double>^ tmsr2;

now I want to allocate it in function so:

void allocate(array<double>^ tmsr2)
{
    tmsr2=gcnew array<double>(100);
}

Now, tmsr2 in function gets allocated well but I lose the pointer when returning to main()
The problem is clear to me, just like if I want to allocate simple array “double *a”; I need to pass pointer to function so “&a” and then everything works fine. I just don’t know the syntax with managed arrays. Help much appreciated.

Peter

Answer 1

Since array<double> is a managed type, you can use a managed tracking reference here, instead of a plain reference.

void allocate(array<double>^% tmsr2)
{
    tmsr2 = gcnew array<double>(100);
}

Here’s my test app:

public ref class AsAClassField
{
public:
    array<double>^ b;

    AsAClassField()
    {
        allocate(b);
        Debug::WriteLine("b = " + (b != nullptr ? "array" : "null"));
    }
};

int main(array<System::String ^> ^args)
{
    array<double>^ a = nullptr;
    allocate(a);
    Debug::WriteLine("a = " + (a != nullptr ? "array" : "null"));
    AsAClassField^ foo = gcnew AsAClassField();

    return 0;
}

Output:

a = array
b = array

---

Of course, you could always switch your allocate function to return the newly allocated array, rather than taking it as a reference. That would be more in the managed style.