[LLVMdev] Struct layout assumptions

[Gordon Henriksen]

On Mar 2, 2008, at 15:47, Talin wrote:

> OK, so we come to the issue of inheritance: Suppose I have a class A  
> and subclass B, each of which have two methods.
>
>    A.vtable = { A.method1 *, A.method2 * }
>    B.vtable = { { A.method1 *, A.method2 * }, B.method1 *, B.method2  
> * }
>
>    A.vtable = { A.method1 *, A.method2 * }
>    B.vtable = { A.method1 *, A.method2 *, B.method1 *, B.method2 * }
>
> However, the problem here is that I don't know if its legal to  
> bitcast from B.vtable to A.vtable. As far as I know, the optimizer  
> might re-order the member fields, or muck with the padding.

Hi Talin,

Either form is perfectly safe.

— Gordon