svn commit: r337426 - head/sbin/ifconfig

[Mark Johnston]

On Fri, Aug 10, 2018 at 10:25:50AM +1000, Bruce Evans wrote:
> On Tue, 7 Aug 2018, Mark Johnston wrote:
> 
> > Log:
> >  ifconfig: Fix use of _Noreturn.
> >
> >  The _Noreturn is a function-specifier (like inline) which must preceed
> >  the declarator.
> >
> >  Submitted by:	Sebastian Huber <sebastian.huber at embedded-brains.de>
> >  MFC after:	1 week
> 
> _Noreturn is even more broken than I knew.  It should never be used.  Here
> its use is wronger than usual.
> 
> > Modified: head/sbin/ifconfig/ifconfig.c
> > ==============================================================================
> > --- head/sbin/ifconfig/ifconfig.c	Tue Aug  7 17:13:42 2018	(r337425)
> > +++ head/sbin/ifconfig/ifconfig.c	Tue Aug  7 17:25:38 2018	(r337426)
> > @@ -109,7 +109,7 @@ static	int ifconfig(int argc, char *const *argv, int i
> > static	void status(const struct afswtch *afp, const struct sockaddr_dl *sdl,
> > 		struct ifaddrs *ifa);
> > static	void tunnel_status(int s);
> > -static	void usage(void) _Noreturn;
> > +static _Noreturn void usage(void);
> >
> > static struct afswtch *af_getbyname(const char *name);
> > static struct afswtch *af_getbyfamily(int af);
> 
> FreeBSD code should use __dead2 since it is more portable (within
> FreeBSD) and doesn't have so mean syntactical restrictions.  However,
> it only exists at all since it had similar syntactial restrictions
> when it was new (FreeBSD-1 used __dead, which must be placed like
> _Noreturn, but __dead2 uses __attribute__(()) which couldn't be placed
> there when it was new), and the macro that hides the details was renamed
> to inhibit misuse.  Changing __dead2 to _Noreturn and moving it to satisfy
> the restricted syntax of the latter mainly broke support for old compilers
> where __dead2 cannot be placed there.

__dead2 was never present.  _Noreturn was added in r317755, apparently
to appease Coverity.

> However, all declarations of static usage() as non-returning are bogus, ...

I can only agree, especially since exit() is already declared with
_Noreturn in stdlib.h.  I don't understand why __dead2/_Noreturn keeps
getting added to various usage() declarations.