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SubjectRe: [PATCH v2 2/2] r8169: Avoid pointer aliasing
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On Tue, 2019-02-05 at 11:14 -0800, David Miller wrote:
> From: Joe Perches <joe@perches.com>
> Date: Tue, 05 Feb 2019 10:42:54 -0800
>
> > On Mon, 2019-02-04 at 19:20 -0800, David Miller wrote:
> >> From: Thierry Reding <thierry.reding@gmail.com>
> >> Date: Mon, 4 Feb 2019 17:42:13 +0100
> >>
> >> > @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
> >> > static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
> >> > {
> >> > const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
> >> > - u8 mac_addr[ETH_ALEN] __aligned(4) = {};
> >> > + u8 mac_addr[ETH_ALEN] = {};
> >> > struct rtl8169_private *tp;
> >>
> >> I agree with Heiner, you have to provide at least 2 byte alignment for this
> >> buffer due to the reasons he stated.
> >
> > It's declared after a pointer so it is already is 2 byte aligned.
> >
> > A lot of drivers wouldn't work otherwise.
>
> That's assuming a lot about what the compiler will do when nit allocates
> local variables to the stack.

It's also assuming what a compiler will do when
it defines a struct.

> I want it _explicit_.

Your choice, but there are a _lot_ of existing uses
and I think requiring it is as senseless as requiring
void * arithmetic to be cast to char * as gcc and
clang already do not add padding after a pointer.


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