Pointer assignment in C++. (Pointer to a pointer to pointer is on the LHS)

Question

IDirect3DSurface9 *var = NULL;

IDirect3DSurface9 *** ret;

I want to assign the value dereferenced by var into the variable pointed by ret.

I did the foll:

(*(*(ret[0]))) = var;

I feel this is correct C++ syntax. But why is that I am getting compilation error as follows:

error C2679: binary '=' : no operator found which takes right hand operand of type "IDirect3DSurface9 *" (or these is no acceptable conversion).

What is the correct syntax?

Answer 1

You have de-referenced the pointer 3 times. Once when you treated it as an array and used the index [0], and then twice more with the * operator. In order to be compatible with var you should de-reference only twice.

To be more explicit, let's break this down:

• ret has type IDirect3DSurface9***.
• ret[0] has type IDirect3DSurface9**.
• *(ret[0]) has type IDirect3DSurface9*.
• *(*(ret[0])) has type IDirect3DSurface9.

And clearly it follows that *(*(ret[0])) is not assignment compatible with var which has type IDirect3DSurface9*.

As to what your code really should be, I could not say for sure, but you will need to remove one level of indirection.