Re: [Qemu-devel] [PATCH] vhost_net: fix misuse of assert()

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

On Fri, 19 Jun 2015 16:06:04 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Fri, Jun 19, 2015 at 04:00:05PM +0200, Markus Armbruster wrote:
> > "Michael S. Tsirkin" <mst@redhat.com> writes:
> > 
> > > On Fri, Jun 19, 2015 at 12:55:57PM +0200, Markus Armbruster wrote:
> > >> "Michael S. Tsirkin" <mst@redhat.com> writes:
> > >> 
> > >> > On Fri, Jun 19, 2015 at 11:13:40AM +0100, Peter Maydell wrote:
> > >> >> On 19 June 2015 at 11:07, Michael S. Tsirkin <mst@redhat.com> wrote:
> > >> >> > On Fri, Jun 19, 2015 at 12:00:53PM +0200, Greg Kurz wrote:
> > >> >> >> In case NDEBUG is defined, assert() expands to nothing and
> > >> >> >> vhost_net_set_vnet_endian() doesn't get called...
> > >> >> >>
> > >> >> >> Suggested-by: Thomas Huth <thuth@redhat.com>
> > >> >> >> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> > >> >> >
> > >> >> > Not sure what the point is.
> > >> >> > We don't support building with NDEBUG.
> > >> >> 
> > >> >> Putting functional behaviour inside an assert() is still a really
> > >> >> bad idea. If you're reading the code you probably skim over the
> > >> >> assert() as not functionally relevant...
> > >> >> 
> > >> >> -- PMM
> > >> >
> > >> > I can apply this if commit log explains it's a readability
> > >> > enhancement, not a bugfix.
> > >> 
> > >> Easy:
> > >> 
> > >> vhost_net: fix misuse of assert()
> > >> 
> > >> In case NDEBUG is defined, assert() expands to nothing and
> > >> vhost_net_set_vnet_endian() doesn't get called...
> > >> 
> > >> Suggested-by: Thomas Huth <thuth@redhat.com>
> > >> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> > >> 
> > >> We don't support building with NDEBUG, but putting functional behaviour
> > >> inside an assert() is still a really bad idea.  If you're reading the
> > >> code you probably skim over the assert() as not functionally relevant...
> > >> 
> > >> Signed-off-by: Michael S. Tsirkin" <mst@redhat.com>
> > >
> > > Pls submit v2 in the regular format - I can rewrite the commit log
> > > but prefer not to, as it doesn't scale. There's no need to add my
> > > signature though, git am -s does this automatically.
> > 
> > I *hate* it when maintainers rewrite my commit message, then claim it's
> > mine :)
> > 
> > But that's not what I suggested!  I suggested to append the additional
> > explanation you want after Greg's S-o-B.  Makes it obvious that it's
> > yours.
> 
> Well both the subject and the original commit log are irrelevant IMO:
> why mention NDEBUG when we don't support it? So it's not really
> a misuse.
> 

Hmmm... I got obviously un-Cc'd from this thread at some point... but
anyway I've sent a v2 with a more comprehensive log. The subject stays
the same though: putting relevant code in assert() is wrong, even from
a code reading POV.

> > I think that scales just fine in a simple case like this where you
> > already know the explanation.
>