Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 8 Jul 2022 16:47:59 -0700 | Subject | Re: [PATCH] amd-xgbe: fix clang -Wformat warnings |
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On Fri, Jul 8, 2022 at 4:27 PM Justin Stitt <justinstitt@google.com> wrote: > > When building with Clang we encounter the following warning: > | drivers/net/ethernet/amd/xgbe/xgbe-dcb.c:234:42: error: format specifies > | type 'unsigned char' but the argument has type '__u16' (aka 'unsigned > | short') [-Werror,-Wformat] pfc->pfc_cap, pfc->pfc_en, pfc->mbc, > | pfc->delay); > > pfc->pfc_cap , pfc->pfc_cn, pfc->mbc are all of type `u8` while pfc->delay is > of type `u16`. The correct format specifiers `%hh[u|x]` were used for > the first three but not for pfc->delay, which is causing the warning > above. > > Variadic functions (printf-like) undergo default argument promotion. > Documentation/core-api/printk-formats.rst specifically recommends using > the promoted-to-type's format flag. In this case `%d` (or `%x` to > maintain hex representation) should be used since both u8's and u16's > are fully representable by an int. > > Moreover, C11 6.3.1.1 states: > (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int > can represent all values of the original type ..., the value is > converted to an int; otherwise, it is converted to an unsigned int. > These are called the integer promotions.` > > Link: https://github.com/ClangBuiltLinux/linux/issues/378 > Signed-off-by: Justin Stitt <justinstitt@google.com>
Thanks for the patch, this fixes an instance of -Wformat I observe for x86_64 allmodconfig. I thought you had already fixed this file up? https://lore.kernel.org/llvm/20220607191119.20686-1-jstitt007@gmail.com/ which was merged. I'm guessing that was from a defconfig, while this was from an allmodconfig? Seems like there's a bunch of config ifdef'ery around the definition of netif_dbg.
Either way, thanks for the patches and
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> --- > For clarification, the first three parameters given to netif_dbg did NOT > cause a -Wformat warning. I changed them simply to follow what the > standard and documentation recommend. > > drivers/net/ethernet/amd/xgbe/xgbe-dcb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c > index 895d35639129..c68ace804e37 100644 > --- a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c > +++ b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c > @@ -230,7 +230,7 @@ static int xgbe_dcb_ieee_setpfc(struct net_device *netdev, > struct xgbe_prv_data *pdata = netdev_priv(netdev); > > netif_dbg(pdata, drv, netdev, > - "cap=%hhu, en=%#hhx, mbc=%hhu, delay=%hhu\n", > + "cap=%d, en=%#x, mbc=%d, delay=%d\n", > pfc->pfc_cap, pfc->pfc_en, pfc->mbc, pfc->delay); > > /* Check PFC for supported number of traffic classes */ > -- > 2.37.0.rc0.161.g10f37bed90-goog >
-- Thanks, ~Nick Desaulniers
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