After commit 3948b05950fd ("net: introduce a config option to tweak
MAX_SKB_FRAGS"), clang warns:
drivers/net/ethernet/ti/netcp_core.c:2085:4: warning: format specifies type 'long' but the argument has type 'int' [-Wformat]
MAX_SKB_FRAGS);
^~~~~~~~~~~~~
include/linux/dev_printk.h:144:65: note: expanded from macro 'dev_err'
dev_printk_index_wrap(_dev_err, KERN_ERR, dev, dev_fmt(fmt), ##__VA_ARGS__)
~~~ ^~~~~~~~~~~
include/linux/dev_printk.h:110:23: note: expanded from macro 'dev_printk_index_wrap'
_p_func(dev, fmt, ##__VA_ARGS__); \
~~~ ^~~~~~~~~~~
include/linux/skbuff.h:352:23: note: expanded from macro 'MAX_SKB_FRAGS'
#define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS
^~~~~~~~~~~~~~~~~~~~
./include/generated/autoconf.h:11789:30: note: expanded from macro 'CONFIG_MAX_SKB_FRAGS'
#define CONFIG_MAX_SKB_FRAGS 17
^~
1 warning generated.
Follow the pattern of the rest of the tree by changing the specifier to
'%u' and casting MAX_SKB_FRAGS explicitly to 'unsigned int', which
eliminates the warning.
Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS")
Signed-off-by: Nathan Chancellor <[email protected]>
---
I am a little confused as to why the solution for this warning is
casting to 'unsigned int' rather than just updating all the specifiers
to be '%d', as I do not see how MAX_SKB_FRAGS can be any type other than
just 'int' but I figured I would be consistent with the other fixes I
have seen around this issue.
---
drivers/net/ethernet/ti/netcp_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/ti/netcp_core.c b/drivers/net/ethernet/ti/netcp_core.c
index 1bb596a9d8a2..d829113c16ee 100644
--- a/drivers/net/ethernet/ti/netcp_core.c
+++ b/drivers/net/ethernet/ti/netcp_core.c
@@ -2081,8 +2081,8 @@ static int netcp_create_interface(struct netcp_device *netcp_device,
netcp->tx_pool_region_id = temp[1];
if (netcp->tx_pool_size < MAX_SKB_FRAGS) {
- dev_err(dev, "tx-pool size too small, must be at least %ld\n",
- MAX_SKB_FRAGS);
+ dev_err(dev, "tx-pool size too small, must be at least %u\n",
+ (unsigned int)MAX_SKB_FRAGS);
ret = -ENODEV;
goto quit;
}
---
base-commit: 3b064f541be822dc095991c6dda20a75eb51db5e
change-id: 20230329-net-ethernet-ti-wformat-acaa86350657
Best regards,
--
Nathan Chancellor <[email protected]>
On Wed, Mar 29, 2023 at 8:08 AM Nathan Chancellor <[email protected]> wrote:
>
> After commit 3948b05950fd ("net: introduce a config option to tweak
> MAX_SKB_FRAGS"), clang warns:
>
> drivers/net/ethernet/ti/netcp_core.c:2085:4: warning: format specifies type 'long' but the argument has type 'int' [-Wformat]
> MAX_SKB_FRAGS);
> ^~~~~~~~~~~~~
> include/linux/dev_printk.h:144:65: note: expanded from macro 'dev_err'
> dev_printk_index_wrap(_dev_err, KERN_ERR, dev, dev_fmt(fmt), ##__VA_ARGS__)
> ~~~ ^~~~~~~~~~~
> include/linux/dev_printk.h:110:23: note: expanded from macro 'dev_printk_index_wrap'
> _p_func(dev, fmt, ##__VA_ARGS__); \
> ~~~ ^~~~~~~~~~~
> include/linux/skbuff.h:352:23: note: expanded from macro 'MAX_SKB_FRAGS'
> #define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS
> ^~~~~~~~~~~~~~~~~~~~
> ./include/generated/autoconf.h:11789:30: note: expanded from macro 'CONFIG_MAX_SKB_FRAGS'
> #define CONFIG_MAX_SKB_FRAGS 17
> ^~
> 1 warning generated.
>
> Follow the pattern of the rest of the tree by changing the specifier to
> '%u' and casting MAX_SKB_FRAGS explicitly to 'unsigned int', which
> eliminates the warning.
>
> Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS")
> Signed-off-by: Nathan Chancellor <[email protected]>
> ---
> I am a little confused as to why the solution for this warning is
> casting to 'unsigned int' rather than just updating all the specifiers
> to be '%d', as I do not see how MAX_SKB_FRAGS can be any type other than
> just 'int' but I figured I would be consistent with the other fixes I
> have seen around this issue.
MAX_SKB_FRAGS might be defined by Kconfig, see:
352 #define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS
in include/linux/skbuff.h. The Kconfig is declared in
net/Kconfig:254.
Because integer literals in C are signed, the cast is necessary to
avoid the format specifier from warning about the wrong signedness.
It would be preferable to have a `U` suffix on the literal value, then
the cast would be unnecessary.
Untested:
```
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 494a23a976b0..67cb6bfc4056 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -349,7 +349,7 @@ struct sk_buff;
# define CONFIG_MAX_SKB_FRAGS 17
#endif
-#define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS
+#define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS ## U
extern int sysctl_max_skb_frags;
```
Perhaps other code using MAX_SKB_FRAGS might have to worry about
signedness and conversions.
But I think what you have is fine for now.
Reviewed-by: Nick Desaulniers <[email protected]>
Though the above might be a longer-term solution since this might pop up again.
> ---
> drivers/net/ethernet/ti/netcp_core.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/ti/netcp_core.c b/drivers/net/ethernet/ti/netcp_core.c
> index 1bb596a9d8a2..d829113c16ee 100644
> --- a/drivers/net/ethernet/ti/netcp_core.c
> +++ b/drivers/net/ethernet/ti/netcp_core.c
> @@ -2081,8 +2081,8 @@ static int netcp_create_interface(struct netcp_device *netcp_device,
> netcp->tx_pool_region_id = temp[1];
>
> if (netcp->tx_pool_size < MAX_SKB_FRAGS) {
> - dev_err(dev, "tx-pool size too small, must be at least %ld\n",
> - MAX_SKB_FRAGS);
> + dev_err(dev, "tx-pool size too small, must be at least %u\n",
> + (unsigned int)MAX_SKB_FRAGS);
> ret = -ENODEV;
> goto quit;
> }
>
> ---
> base-commit: 3b064f541be822dc095991c6dda20a75eb51db5e
> change-id: 20230329-net-ethernet-ti-wformat-acaa86350657
>
> Best regards,
> --
> Nathan Chancellor <[email protected]>
>
--
Thanks,
~Nick Desaulniers
On Wed, Mar 29, 2023 at 10:10 AM Nick Desaulniers
<[email protected]> wrote:
>
> Because integer literals in C are signed, the cast is necessary to
> avoid the format specifier from warning about the wrong signedness.
> It would be preferable to have a `U` suffix on the literal value, then
> the cast would be unnecessary.
>
> Untested:
> ```
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 494a23a976b0..67cb6bfc4056 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -349,7 +349,7 @@ struct sk_buff;
> # define CONFIG_MAX_SKB_FRAGS 17
> #endif
>
> -#define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS
> +#define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS ## U
Or rather this trick.
https://godbolt.org/z/81aPxf39b
I forget what that's called (it's not xmacros); we definitely have a
macro for that in the kernel.
--
Thanks,
~Nick Desaulniers
Hello:
This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <[email protected]>:
On Wed, 29 Mar 2023 08:08:01 -0700 you wrote:
> After commit 3948b05950fd ("net: introduce a config option to tweak
> MAX_SKB_FRAGS"), clang warns:
>
> drivers/net/ethernet/ti/netcp_core.c:2085:4: warning: format specifies type 'long' but the argument has type 'int' [-Wformat]
> MAX_SKB_FRAGS);
> ^~~~~~~~~~~~~
> include/linux/dev_printk.h:144:65: note: expanded from macro 'dev_err'
> dev_printk_index_wrap(_dev_err, KERN_ERR, dev, dev_fmt(fmt), ##__VA_ARGS__)
> ~~~ ^~~~~~~~~~~
> include/linux/dev_printk.h:110:23: note: expanded from macro 'dev_printk_index_wrap'
> _p_func(dev, fmt, ##__VA_ARGS__); \
> ~~~ ^~~~~~~~~~~
> include/linux/skbuff.h:352:23: note: expanded from macro 'MAX_SKB_FRAGS'
> #define MAX_SKB_FRAGS CONFIG_MAX_SKB_FRAGS
> ^~~~~~~~~~~~~~~~~~~~
> ./include/generated/autoconf.h:11789:30: note: expanded from macro 'CONFIG_MAX_SKB_FRAGS'
> #define CONFIG_MAX_SKB_FRAGS 17
> ^~
> 1 warning generated.
>
> [...]
Here is the summary with links:
- [net-next] net: ethernet: ti: Fix format specifier in netcp_create_interface()
https://git.kernel.org/netdev/net-next/c/3292004c90c8
You are awesome, thank you!
--
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