Re: [PATCH] earlycpio: constify find_cpio_data()'s "data" parameter

[Jan Beulich <jbeulich@suse.com>]

On 28.10.2024 17:18, Andrew Cooper wrote:
> On 28/10/2024 4:12 pm, Jan Beulich wrote:
>> On 28.10.2024 17:07, Andrew Cooper wrote:
>>> On 28/10/2024 4:03 pm, Jan Beulich wrote:
>>>> As with 9cbf61445cda ("xen/earlycpio: Drop nextoff parameter"): While
>>>> this is imported from Linux, the parameter not being pointer-to-const is
>>>> dubious in the first place and we're not plausibly going to gain a write
>>>> through it.
>>>>
>>>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>> You haven't tried compiling this, have you?
>> Of course I have. Is there any subtlety with compiler versions? Or what
>> else am I missing?
> 
> struct cpio_data's copy of this field is non-const (which you keep on
> noting that new compilers will object to),

New compilers? I'm afraid I'm missing context. With gcc14 the patch builds
fine. I didn't try _older_ ones (but I see no reason why they might object;
see below).

> and you can't change that
> without breaking the build in microcode.

I don't need to change that, "thanks" to

			cd.data = (void *)dptr;

casting away const-ness. That is - compilers ought to be fine with the
change; Misra won't like it.

> Nothing of this form can be taken until the constness is consistent in
> microcode, after which yes it can mostly become const.

We can move there in steps, can't we?

Jan