Re: [RFC][PATCH 5/7] trace: make filter_parse_regex() provide the length of substring to compare with

From: Al Viro
Date: Thu Feb 05 2015 - 16:44:30 EST


On Thu, Feb 05, 2015 at 04:29:33PM -0500, Steven Rostedt wrote:
> On Thu, 5 Feb 2015 19:56:38 +0000
> Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> > From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> >
> > ... by passing len by address and using it to report the length of
> > substring in question.
>
> You certainly are very verbose in your change logs.
>
> What exactly is the purpose of this patch? Clean up? Optimization?
>
> I can't really tell. Seems like you are just moving the strlen() from
> outside the function into it.

The point is that by now this strlen() is the only thing for which we
NUL-termination of the substring; moving it inside the filter_parse_regex()
is an obviously equivalent transformation and it leaves that one strlen() call
inside filter_parse_regex() the only place where we still care about NUL.

The next commit kills it off completely, at which point we are done with
modifying the string at all.
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