svn commit: r316826 - head/sys/netpfil/ipfw/nat64

[Ian Lepore]

On Fri, 2017-04-14 at 08:32 -0700, Conrad Meyer wrote:
> On Fri, Apr 14, 2017 at 4:58 AM, Andrey V. Elsukov <ae at freebsd.org>
> wrote:
> > 
> > Author: ae
> > Date: Fri Apr 14 11:58:41 2017
> > New Revision: 316826
> > URL: https://svnweb.freebsd.org/changeset/base/316826
> > 
> > Log:
> >   Avoid undefined behavior.
> > 
> >   The 'pktid' variable is modified while being used twice between
> >   sequence points, probably due to htonl() is macro.
> FYI — there are a ton of similar reports in sys/rpc due to the XDR
> macros (which read a network value off a pointer and increment it).
> See e.g., IXDR_GET_UINT32() macro.
> 
> Best,
> Conrad

Aren't they all false positives, since the macros involved are g'teed
not to evaluate their arguments more than once as written (because
__builtin_constant_p always evaluates at compile time)?  Do we really
want to churn our source code to eliminate false positives from some
tool that appears to still be in its alpha-testing state?

-- Ian