Question

I have a C++ function which returns a std::vector<float>.

I am interfacing with some C code.

How do I change this C++ function so that it returns some pointer to a float array, and how do I save this returned array so that I can use it in my C code?

Answer 1

You could save the returned temporary vector in a vector object with static storage duration.

std::vector<float> foo()
{
    return std::vector<float>();
}

float* call_foo_and_get_pointer()
{
    static std::vector<float> save; // this line is executed only at the first
                                    // call to enclosing function
    save = foo();
    return save.data();  // or &data[0]
}

The pointer returned from call_foo_and_get_pointer is guaranteed to stay valid until the next call to it.