On Wed, 22 May 2019 15:11:10 +0200
Miguel Ojeda <miguel.ojeda.sando...@gmail.com> wrote:
> On Wed, May 22, 2019 at 1:52 PM Steven Rostedt <rost...@goodmis.org> wrote:
> >
> > On Wed, 22 May 2019 11:58:10 +0200
> > Miguel Ojeda <miguel.ojeda.sando...@gmail.com> wrote:
> >
> > > +/* reset all but tr, trace, and overruns */
> > > +static __always_inline void trace_iterator_reset(struct trace_iterator
> > > *iter)
> > > +{
> > > + /*
> > > + * We do not simplify the start address to &iter->seq in order to
> > > let
> > > + * GCC 9 know that we really want to overwrite more members than
> > > + * just iter->seq (-Warray-bounds).
> >
> > This comment is fine for the change log, but here it is too specific.
> > Why does one care about GCC 9 when we are at version GCC 21? I care
> > more about why we are clearing the data and less about the way we are
> > doing it.
>
> Since the code is not written the obvious way on purpose, the idea is
> to document why that is so -- otherwise the reader may wonder (and
> possibly re-introduce it back). Specifying when the warning started
> appearing tends to be clarifying, too.
>
> The commit message explains the change itself, but the comment
> explains why the current code is written like that.
Could also be shorten to: "Keep gcc from complaining about overwriting
more than just one member in the structure."
>
> > A comment like:
> >
> > /*
> > * Reset the state of the trace_iterator so that it can read
> > * consumed data. Normally, the trace_iterator is used for
> > * reading the data when it is not consumed, and must retain
> > * state.
> > */
> >
> > That is more useful than why we have the offset hack.
>
> That comment would be great in the function's description, in my
> opinion, and it is a great addition to have nevertheless. I re-used
> the existing comment for that to keep the change as minimal as
> possible (and nevertheless I am not qualified to write it since I have
> not studied the tracing code). In other words, I'm not saying there
> are no further improvements :-)
I put it there so you have an idea what the rational was ;-)
-- Steve
