On 03 Mar 2015 21:01, Dmitry V. Levin wrote: > On Tue, Mar 03, 2015 at 12:47:19PM -0500, Mike Frysinger wrote: > > build warnings: > > there's still random -Wsign-compare warnings, but i guess we don't care > > about those > > There are exactly 3 different -Wsign-compare warning messages: > socketutils.c:145: warning: comparison between signed and unsigned integer > expressions [-Wsign-compare] > netlink_inet_diag.c:67: warning: comparison between signed and unsigned > integer expressions [-Wsign-compare] > netlink_unix_diag.c:75: warning: comparison between signed and unsigned > integer expressions [-Wsign-compare] > > The only way to fix them is to fix NLMSG_OK macro defined > in <linux/netlink.h>.
hmm, i'm not so sure. the kernel headers declare:
struct nlmsghdr {
__u32 nlmsg_len; /* Length of message including header */
...
#define NLMSG_OK(nlh,len) ((len) >= (int)sizeof(struct nlmsghdr) && \
(nlh)->nlmsg_len >= sizeof(struct nlmsghdr) && \
(nlh)->nlmsg_len <= (len))
and the strace code does:
ssize_t ret;
struct nlmsghdr *h;
...
NLMSG_OK(h, ret);
if the kernel headers provided a function instead of a macro, it'd be:
static bool NLMSG_OK(const struct nlmsghdr *nlh, __u32 len) {...}
which is to say, the API of this macro is that it takes a u32 len, but we're
passing it a ssize_t (as that is what recvmsg/etc... returns). it is annoying
that there's a type mismatch here, but i think the problem is still on our side
to sort out:
NLMSG_OK(h, (size_t)ret)
we've already verified earlier in the code that it's not negative, so the cast
by itself should be safe:
ret = recvmsg(fd, &msg, 0);
if (ret < 0) {
if (errno == EINTR)
continue;
return false;
}
-mike
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