Paul Eggert <eggert@cs.ucla.edu> schrieb am Mi., 17. Mai 2017 um 22:38 Uhr:

> On 05/15/2017 02:04 AM, Philipp Stephani wrote:
> > - Maybe add verify(INT_MAX >= TYPE_MAXIMUM(in_port_t)) and
> > verify(TYPE_MINIMUM(in_port_t) == 0) to make sure that we can use int
> > for the port?
>
> The code has been changed so that the port number is no longer stored in
> an int so this remark is obsolete now. However, if this issue crops up
> later I don't think we need to worry about it for IPv4 and IPv6 ports,
> since they're always in the range 0..65535. Emacs already assumes that
> 'int' is at least 32 bits wide, as per POSIX.
>

Yes, these static assertions are more for documenting the assumptions that
the code makes in a way that actually checks the assumptions.


>
> > - Should there be a guard against the alias violation, e.g. by
> > declaring sa and sa1 with __attribute__((may_alias))? Otherwise it's
> > UB and the compiler might elide the switch entirely.
>
> Yes, that is easy enough to do and would avoid some unlikely but
> hard-to-catch bugs. I installed the attached. Most likely other parts of
> Emacs should use may_alias too; do you happen to have any tool in your
> toolbox that would find them systematically?
>
>
A type-based aliasing sanitizer is currently being added to Clang. Once
that is landed I'll run it over the Emacs codebase.