svn commit: r309658 - head/sys/vm

[Mark Johnston]

On Wed, Dec 07, 2016 at 11:44:49AM +1100, Bruce Evans wrote:
> On Tue, 6 Dec 2016, Mark Johnston wrote:
> 
> > Log:
> >  Provide dummy sysctls for v_cache_count and v_tcached.
> >
> >  Some utilities (notably top(1)) exit if any of their input sysctls don't
> >  exist, and the removal of the above-mentioned PG_CACHE-related sysctls
> >  makes it difficult to run such utilities on different versions of the
> >  kernel without recompiling.
> >
> >  Requested by:	bde
> 
> Thanks.
> 
> > Modified: head/sys/vm/vm_meter.c
> > ==============================================================================
> > --- head/sys/vm/vm_meter.c	Tue Dec  6 22:48:28 2016	(r309657)
> > +++ head/sys/vm/vm_meter.c	Tue Dec  6 22:52:45 2016	(r309658)
> > @@ -314,3 +314,14 @@ VM_STATS_VM(v_forkpages, "VM pages affec
> > VM_STATS_VM(v_vforkpages, "VM pages affected by vfork()");
> > VM_STATS_VM(v_rforkpages, "VM pages affected by rfork()");
> > VM_STATS_VM(v_kthreadpages, "VM pages affected by fork() by kernel");
> > +
> > +#ifndef BURN_BRIDGES
> > +/*
> > + * Provide compatibility sysctls for the benefit of old utilities which exit
> > + * with an error if they cannot be found.
> > + */
> > +SYSCTL_UINT(_vm_stats_vm, OID_AUTO, v_cache_count, CTLFLAG_RD,
> > +    (u_int *)NULL, 0, "Dummy for compatibility");
> > +SYSCTL_UINT(_vm_stats_vm, OID_AUTO, v_tcached, CTLFLAG_RD,
> > +    (u_int *)NULL, 0, "Dummy for compatibility");
> > +#endif
> 
> I don't like casting NULL, but SYSCTL_* enforces type safety for pointers
> to variables in a way that breaks normal use of NULL.
> 
> You are supposed to obfuscate this by spelling the value as SYSCTL_UINT_NULL.
> This is actually documented in sysctl(9).

Fixed, thanks - I somehow managed to miss those #defines when I was
looking at sysctl.h to see why a plain "NULL" doesn't work there.