From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: [PATCH] netlink: fix gcc -Wconversion compilation warning Date: Mon, 13 Dec 2010 13:35:25 -0800 Message-ID: References: <1292259913-9911-1-git-send-email-kirill@shutemov.name> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , netdev@vger.kernel.org, Pablo Neira Ayuso , "Dmitry V. Levin" , linux-kernel@vger.kernel.org To: "Kirill A. Shutsemov" Return-path: In-Reply-To: <1292259913-9911-1-git-send-email-kirill@shutemov.name> (Kirill A. Shutsemov's message of "Mon, 13 Dec 2010 19:05:13 +0200") Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org "Kirill A. Shutsemov" writes: > From: Dmitry V. Levin > > $ cat << EOF | gcc -Wconversion -xc -S -o/dev/null - > unsigned f(void) {return NLMSG_HDRLEN;} > EOF > : In function 'f': > :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 > Signed-off-by: Kirill A. Shutemov > --- > 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))