Re: [PATCH] iwlwifi: pcie: fix constant-conversion warning

[Arnd Bergmann <arnd@kernel.org>]

On Wed, Nov 10, 2021 at 10:38 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Thu, Nov 4, 2021 at 6:37 AM Arnd Bergmann <arnd@kernel.org> wrote:
> >
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > clang points out a potential issue with integer overflow when
> > the iwl_dev_info_table[] array is empty:
> >
> > drivers/net/wireless/intel/iwlwifi/pcie/drv.c:1344:42: error: implicit conversion from 'unsigned long' to 'int' changes value from 18446744073709551615 to -1 [-Werror,-Wconstant-conversion]
> >         for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
> >                ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
> >
> > This is still harmless, as the loop correctly terminates, but adding
> > an (int) cast makes that clearer to the compiler.
> >
> > Fixes: 3f7320428fa4 ("iwlwifi: pcie: simplify iwl_pci_find_dev_info()")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> >  drivers/net/wireless/intel/iwlwifi/pcie/drv.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> > index c574f041f096..81e8f2fc4982 100644
> > --- a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> > +++ b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> > @@ -1341,7 +1341,7 @@ iwl_pci_find_dev_info(u16 device, u16 subsystem_device,
> >  {
> >         int i;
> >
> > -       for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
> > +       for (i = (int)ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
>
> Perhaps `i` could be a `size_t` instead of an `int`?
>
> size_t i = ARRAY_SIZE(iwl_dev_info_table);
> while (i--) {
>   ...

I imagine 'i' is idiomatically 'int' in inner iterations.

I've sent a different fix now.

        Arnd