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Message-ID: <m1oc8jlg92.fsf@fess.ebiederm.org> Date: Fri, 17 Dec 2010 22:58:01 -0800 From: ebiederm@...ssion.com (Eric W. Biederman) To: David Miller <davem@...emloft.net> Cc: kirill@...temov.name, netdev@...r.kernel.org, pablo@...filter.org, ldv@...linux.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] netlink: fix gcc -Wconversion compilation warning David Miller <davem@...emloft.net> writes: > From: ebiederm@...ssion.com (Eric W. Biederman) > Date: Mon, 13 Dec 2010 13:35:25 -0800 > >> "Kirill A. Shutsemov" <kirill@...temov.name> writes: >> >>> From: Dmitry V. Levin <ldv@...linux.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. > > What are you talking about? That's exactly his test case, > look at what NLMSG_HDRLEN is defined to, it's exactly the > case you're worried "will fail", it passes sizeof() to > NLMSG_ALIGN. > > I think I'll apply Kirill's original patch, it's good enough > and simpler. Probably. The case I was worried about was masks that become 0xffffffxx on 64bit instead of 0xffffffffffffxx. Especially when mixing those with ints. It is possible to get some really weird things. Eric -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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