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SubjectRe: [PATCH] netlink: fix gcc -Wconversion compilation warning
"Kirill A. Shutsemov" <kirill@shutemov.name> writes:

> From: Dmitry V. Levin <ldv@altlinux.org>
>
> $ cat << EOF | gcc -Wconversion -xc -S -o/dev/null -
> unsigned f(void) {return NLMSG_HDRLEN;}
> EOF
> <stdin>: In function 'f':
> <stdin>:3:26: warning: negative integer implicitly converted to unsigned type
>
This doesn't look like a bad fix, but I believe things will fail if
we give NLMSG_ALIGN an unsigned long like size_t. Say like sizeof.

Admittedly it has to be a huge size but still if we are going
to go fixing things...

And then there is the silliness that NLMSG_HDRLEN forces itself
to be an int, when it start out as a size_t.

So I think NLMSG_ALIGN either needs to operation exclusively
on unsigned longs aka size_t, or it needs to be type preserving.

Do you have time to look at this a bit more?


> Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
> Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> ---
> include/linux/netlink.h | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/netlink.h b/include/linux/netlink.h
> index 1235669..e2b9e63 100644
> --- a/include/linux/netlink.h
> +++ b/include/linux/netlink.h
> @@ -70,7 +70,7 @@ struct nlmsghdr {
> Check NLM_F_EXCL
> */
>
> -#define NLMSG_ALIGNTO 4
> +#define NLMSG_ALIGNTO 4U
> #define NLMSG_ALIGN(len) ( ((len)+NLMSG_ALIGNTO-1) & ~(NLMSG_ALIGNTO-1) )
> #define NLMSG_HDRLEN ((int) NLMSG_ALIGN(sizeof(struct nlmsghdr)))
> #define NLMSG_LENGTH(len) ((len)+NLMSG_ALIGN(NLMSG_HDRLEN))


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