Re: [PATCH v8 2/9] platform: cznic: Add preliminary support for Turris Omnia MCU

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Thu, May 2, 2024 at 10:18 PM Marek Behún <kabel@xxxxxxxxxx> wrote:
> On Thu, May 02, 2024 at 09:47:25PM +0300, Andy Shevchenko wrote:
> > On Thu, May 2, 2024 at 9:40 PM Marek Behún <kabel@xxxxxxxxxx> wrote:
> > > On Tue, Apr 30, 2024 at 06:17:45PM +0300, Andy Shevchenko wrote:
> > > > On Tue, Apr 30, 2024 at 04:05:07PM +0200, Marek Behún wrote:
> > > > > On Tue, 30 Apr 2024 15:53:51 +0300
> > > > > Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote:
> > > > > > On Tue, Apr 30, 2024 at 2:51 PM Marek Behún <kabel@xxxxxxxxxx> wrote:

...

> > > > > > > +static int omnia_get_version_hash(struct omnia_mcu *mcu, bool bootloader,
> > > > > > > +                                 u8 version[static OMNIA_FW_VERSION_HEX_LEN])
> > > > > >
> > > > > > Interesting format of the last parameter. Does it make any difference
> > > > > > to the compiler if you use u8 *version?
> > > > >
> > > > > The compiler will warn if an array with not enough space is passed as
> > > > > argument.
> > > >
> > > > Really?
> > >
> > > Indeed:
> > >
> > >   extern void a(char *x);
> > >
> > >   static void b(char x[static 10]) {
> > >       a(x);
> > >   }
> > >
> > >   void c(void) {
> > >       char x[5] = "abcd";
> >
> > >       b(x);
> >
> > It's not the example I was talking about. Here should be a(x).
>
> Somehow I got lost. Let's return to my function, where I have
>   int omnia_get_version_hash(..., u8 version[static 40]);
>
> and then I use this function:
>
>   u8 version[40];
>   omnia_get_version_hash(..., version);
>
> If somehow I made a mistake and declared the version array shorter:
>   u8 version[20];
>   omnia_get_version_hash(..., version);
> I would get a warning.

Yes. Would you get the same warning if you replace the parameter to a pointer?

> So the purpose is to get warned if the compiler can prove that there is
> not enough space in the destination buffer.


-- 
With Best Regards,
Andy Shevchenko