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SubjectRe: [RFC PATCH] <linux/taggedptr.h>: Introduce tagged pointer
On Thu, Jun 28, 2018 at 05:06:29PM +0800, Gao Xiang wrote:
> Therefore, this patch introduces simple generic methods to fold
> tags into a pointer integer. It currently reuses the last 2 bits
> of the pointer for tags, which are safely for all modern platforms.

The m68k people will have your head. alignof(unsigned long) == 2 on
m68k. Now, kmalloc always returns 8-byte aligned quantities, but
if you have:

static unsigned long foo;

then ((unsigned long)&foo & 2) may be non-zero.

> +/*
> + * mark these special integers as another type
> + * in order to highlight the tagged pointer usage.
> + */
> +typedef uintptr_t taggedptr_t;

I find this a bit verbose. How about tagptr_t ?

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