linux-kernel - Re: [PATCH v5 06/21] perf script: Move find

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Message-ID: <CAP-5=fUz_LSJ4v4aaAWoLMQRXAtsqeQSjcyRun2kBVXUHTzvUA@mail.gmail.com>
Date: Mon, 4 Nov 2024 14:20:30 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	James Clark <james.clark@...aro.org>, Howard Chu <howardchu95@...il.com>, 
	Athira Jajeev <atrajeev@...ux.vnet.ibm.com>, Michael Petlan <mpetlan@...hat.com>, 
	Veronika Molnarova <vmolnaro@...hat.com>, Dapeng Mi <dapeng1.mi@...ux.intel.com>, 
	Thomas Richter <tmricht@...ux.ibm.com>, Ilya Leoshkevich <iii@...ux.ibm.com>, 
	Colin Ian King <colin.i.king@...il.com>, Weilin Wang <weilin.wang@...el.com>, 
	Andi Kleen <ak@...ux.intel.com>, Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v5 06/21] perf script: Move find_scripts to browser/scripts.c

On Mon, Nov 4, 2024 at 2:09 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Mon, Nov 04, 2024 at 01:06:35PM -0800, Ian Rogers wrote:
> > On Mon, Nov 4, 2024 at 1:00 PM Namhyung Kim <namhyung@...nel.org> wrote:
> > >
> > > On Mon, Nov 04, 2024 at 12:48:01PM -0800, Ian Rogers wrote:
> > > > Namhyung was asking that the c&p of code be 1 patch then "add new
> > > > changes like using openat() on top". That is:
> > > >
> > > > patch 1: add is_directory_at - introduce the 2 line helper function
> > > > patch 2: move the code
> > > > patch 3: update the code to use is_directory_at
> > > >
> > > > patch 2 is known broken as patch 3 is fixing it.
> > > >
> > > > Hopefully this is clear.
> > >
> > > Actually I don't care about the patch ordering.  My request is not
> > > to break build and just to separate different changes out. :)
> >
> > So, patch 2 can't be separated from patch 3 - are we agreed? So we
> > squash patch 2 with patch 3. Patch 1 is trivial and fails to meet the
> > bar of a meaningful change, so we squash that. We end up with this
> > patch. If there's a later revert and a dependence of the 2 liner, just
> > don't revert that part of the change. We've never had such a revert so
> > it is hard to see why we need to generate so much churn because of it.
>
> As I said the patch 1 should be the c&p and no need to introduce
> is_directory_at() before that.  Why not doing
>
>  patch1: move the code
>  patch2: add and use is_directory_at() + openat()
>
> ?

Because placing all the code in 1 file expands GCC's analysis and the
build fails. In the commit message I describe this:
"The arrays are warned about potential buffer overflows by GCC now
that all the code exists in a single C file."
A standard unsound workaround to this is to change "sizeof(...)" to
"sizeof(...) - 1", as it is ugly I added is_directory_at to not suffer
the problem as the arrays are gone.

Thanks,
Ian