Re: [PATCH 2/2] radix-tree: Fix optimisation problem

From: Linus Torvalds
Date: Sat Sep 24 2016 - 20:18:46 EST

On Sat, Sep 24, 2016 at 4:35 PM, Cedric Blancher
<cedric.blancher@xxxxxxxxx> wrote:
>> void *entry = parent->slots[offset];
>> int siboff = entry - parent->slots;
> If entry is a pointer to void, how can you do pointer arithmetic with it?

It's actually void **.

(That said, gcc has an extension that considers "void *" to be a byte
pointer, so you can actually do arithmetic on them, and it acts like
"char *")

> Also, if you use pointer distances, the use of int is not valid, it
> should then be ptrdiff_t siboff.

The use of "int" is perfectly valid, since it's limited by
RADIX_TREE_MAP_SIZE, so it's going to be a small integer.