Re: CVS commit: src/sys/dev/usb

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sat, Apr 21, 2018 at 09:37:46AM +0200, Martin Husemann wrote:
> On Sat, Apr 21, 2018 at 09:30:20AM +0200, Manuel Bouyer wrote:
> > > > 
> > > >-       axe_cmd(sc, AXE_CMD_WRITE_MCAST, 0, 0, (void *)&hashtbl);
> > > >+       axe_cmd(sc, AXE_CMD_WRITE_MCAST, 0, 0, hashtbl);
> > > >
> > > >missing & ?
> > > 
> > >         uint8_t hashtbl[8] = { 0, 0, 0, 0, 0, 0, 0, 0 }; 
> > 
> > So I guess the code was wrong before; not sure how multicast could have
> > worked.
> 
> No, the address is only needed as rhs of the cast. If passed directly,
> the address will be used (due to arrays being passed as pointer to first
> element in C).
> 
> Try it:
> 
> #include <stdio.h>
> #include <inttypes.h>
> 
> int main(void)
> {
>         static uint8_t hashtbl[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
> 
>         printf("%p vs %p\n", (void *)&hashtbl, hashtbl);
>         return 0;
> }

I didn't know this. hashtbl and &hashtbl[0] are equivalent, and I would
assume that &hashtbl is always a pointer to pointer. So the behavior depends
on hashtbl being declared as pointer or as array ?
this is confusing ...

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--