On 5 Mar 2020, at 18:44, Gleb Smirnoff <gleb...@freebsd.org> wrote: > > On Thu, Mar 05, 2020 at 08:35:15PM +0300, Slawa Olhovchenkov wrote: > S> > > D> sbin/mount_nfs/mount_nfs.c:549:10: error: cast from 'char *' to > 'struct > S> > > D> if_msghdr *' increases required alignment from 1 to 4 > S> > > D> [-Werror,-Wcast-align] > S> > > D> ifm = (struct if_msghdr *)buf; > S> > > D> ^~~~~~~~~~~~~~~~~~~~~~~ > S> > > D> 1 error generated. > S> > > D> > S> > > D> In practice I don't think the buffer can ever get misaligned, so > can you > S> > > D> please add a NO_WCAST_ALIGN= to the Makefile? > S> > > > S> > > route(8) handles the same problem via intermediate (void *) cast. What > is > S> > > preferred way to solve the problem? Change compiler flags file wide, or > S> > > just through (void *) cast? > S> > > S> > Copy to aligned buffer or got SIGBUS on some architectures? > S> > S> char buf[2048] __aligned(__alignof(struct if_msghdr)); > S> > S> resolve this watning. > > Thanks, Slawa! I think this is the most elegant solution.
Why don't just declare the buffer as: struct if_msghdr buf; and then do: nread = read(s, &buf, sizeof buf); ? You are never reading more than one if_msghdr anyway, and then there is no need to cast anything. -Dimitry
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