How to assign pointer to pointer?

Question

I have such method

void TetStreamRender::releaseManagerAndGetNextOne(TetFrameManager * manager,
                                                      ObjPool<TetFrameManager> * objPool,
                                                      SafeQueue<TetFrameManager *> * fifo)
    {
        ...

        manager = fifo->dequeue();
    }

also method fifo->dequeue() return TetFrameManager *, so I assume that manager should get new pointer returned by dequeue() method. So, I pass to releaseManagerAndGetNextOne() pointer to TetFrameManager and at the end I expect that this pointer get new pointer, but it doesn't.

Actually if I change this method like this

TetFrameManager * TetStreamRender::releaseManagerAndGetNextOne(TetFrameManager * manager,
                                                      ObjPool<TetFrameManager> * objPool,
                                                      SafeQueue<TetFrameManager *> * fifo)
    {
        ...

        return fifo->dequeue();
    }

It works fine. But question is why in my first example pointer assignment doesn't work as expected?

The way you do it in your first method, your pass a copy of the pointer, and then assign fifo->dequeue() to that copy. — melk
– melk, Commented Apr 10, 2020 at 11:13

NutCracker · Accepted Answer · 2020-04-10 11:03:16Z

1

You can pass reference to pointer like:

void TetStreamRender::releaseManagerAndGetNextOne(TetFrameManager *& manager,
                                                  ObjPool<TetFrameManager> * objPool,
                                                  SafeQueue<TetFrameManager *> * fifo)
{
    // ...
    manager = fifo->dequeue();
}

answered Apr 10, 2020 at 11:03

NutCracker

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