Re: [Qemu-devel] [PATCH v2 14/20] memory-device: ids of virtio based devices are special

[Eric Blake]

On 08/31/2018 06:18 AM, David Hildenbrand wrote:

> > > > > -                error_setg(errp, "address range conflicts with '%s'", d->id);
> > > > > +                error_setg(errp, "address range conflicts with '%s'",
> > > > > +                           id ? id : 0);
> > > >
> > > > What's that 'id ? id : 0' trick for?
> > >
> > > 0 -> "", then it actually makes sense :)

> qemu-system-x86_64: -device pc-dimm,memdev=mem1,addr=0x140000000:
> address range conflicts with '(null)'
>
> (I thought providing NULL would lead to a crash, but it is actually
> handled properly)

Well, glibc handles it. But POSIX says it is undefined, and there are 
other libc where it indeed crashes.  It's better to pass an explicit 
non-null placeholder than to rely on glibc turning NULL into "(null)".

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org