Question Why do PinGCArrayAndGetDataAddress & AddressOf return different addresses ?

In the below code snipped addresses in the variables _TData and _PData are different, Dereferencing _PData gives the correct value where as _TData returns garbage value. Is the difference cuz of, in case of PinGCObjectAndGetAddress the struct is passed by value. If that's the case how do you pin a struct value ?

Code (CSharp):

1.            
2. var vector = new Vector3(1,10,1);
3.  
4. _TData = UnsafeUtility.PinGCObjectAndGetAddress(vector, out _gc);
5. _PData = UnsafeUtility.AddressOf(ref vector);
6.  

I am trying to avoid nested native containers. I have a struct with native array as a member. So to have a Native array of theses structs I though I can store the pointers to the structs in a native array and dereference them when required and for this pinning is essential.

 

Pretty sure you are on the money here. You are boxing the struct then pinning the object.

 

Even if that's happening (I don't mind the address being different) why would dereferencing _TData return a Vector3 with garbage value. If the boxed object it pinned shouldn't it also have the same values ?

 

The address of the box isn't necessarily the address of the actual value in the box - you could be looking at the managed object header. If I were to guess, you need to offset the address by a couple of

sizeof(IntPtr) 

s.

(Not that this will help you in any way - take a look at NativeReference<T> if you haven't already, it might be a better way to stash a struct and get a pointer to it)