linux-kernel - Re: [PATCH 1/1 fyi] perf python: Fix splitting CC into compiler and options

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Date:   Thu, 22 Dec 2022 13:07:22 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Khem Raj <raj.khem@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Fangrui Song <maskray@...gle.com>,
        Ian Rogers <irogers@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        John Keeping <john@...anate.com>, Leo Yan <leo.yan@...aro.org>,
        Michael Petlan <mpetlan@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1 fyi] perf python: Fix splitting CC into compiler and options

On Thu, Dec 22, 2022 at 1:00 PM Arnaldo Carvalho de Melo
<arnaldo.melo@...il.com> wrote:
>
>
>
> On December 22, 2022 2:45:57 PM GMT-03:00, Nick Desaulniers <ndesaulniers@...gle.com> wrote:
> >On Thu, Dec 22, 2022 at 6:34 AM Arnaldo Carvalho de Melo
> ><acme@...nel.org> wrote:
> >>
> >> Just fyi, I'm carrying this in the perf tools tree.
> >>
> >> - Arnaldo
> >>
> >> ----
> >>
> >> Noticed this build failure on archlinux:base when building with clang:
> >>
> >>   clang-14: error: optimization flag '-ffat-lto-objects' is not supported [-Werror,-Wignored-optimization-argument]
> >>
> >> In tools/perf/util/setup.py we check if clang supports that option, but
> >> since commit 3cad53a6f9cdbafa ("perf python: Account for multiple words
> >> in CC") this got broken as in the common case where CC="clang":
> >>
> >>   >>> cc="clang"
> >>   >>> print(cc.split()[0])
> >>   clang
> >>   >>> option="-ffat-lto-objects"
> >>   >>> print(str(cc.split()[1:]) + option)
> >>   []-ffat-lto-objects
> >>   >>>
> >>
> >> And then the Popen will call clang with that bogus option name that in
> >> turn will not produce the b"unknown argument" or b"is not supported"
> >> that this function uses to detect if the option is not available and
> >> thus later on clang will be called with an unknown/unsupported option.
> >>
> >> Fix it by looking if really there are options in the provided CC
> >> variable, and if so override 'cc' with the first token and append the
> >> options to the 'option' variable.
> >>
> >> Fixes: 3cad53a6f9cdbafa ("perf python: Account for multiple words in CC")
> >> Cc: Adrian Hunter <adrian.hunter@...el.com>
> >> Cc: Fangrui Song <maskray@...gle.com>
> >> Cc: Florian Fainelli <f.fainelli@...il.com>
> >> Cc: Ian Rogers <irogers@...gle.com>
> >> Cc: Jiri Olsa <jolsa@...nel.org>
> >> Cc: John Keeping <john@...anate.com>
> >> Cc: Khem Raj <raj.khem@...il.com>
> >> Cc: Leo Yan <leo.yan@...aro.org>
> >> Cc: Michael Petlan <mpetlan@...hat.com>
> >> Cc: Namhyung Kim <namhyung@...nel.org>
> >> Cc: Nathan Chancellor <nathan@...nel.org>
> >> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> >> Cc: Sedat Dilek <sedat.dilek@...il.com>
> >> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> >> ---
> >>  tools/perf/util/setup.py | 13 +++++++++++--
> >>  1 file changed, 11 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tools/perf/util/setup.py b/tools/perf/util/setup.py
> >> index 4f265d0222c454e2..c294db713677c0c2 100644
> >> --- a/tools/perf/util/setup.py
> >> +++ b/tools/perf/util/setup.py
> >> @@ -3,11 +3,20 @@ from subprocess import Popen, PIPE
> >>  from re import sub
> >>
> >>  cc = getenv("CC")
> >> -cc_is_clang = b"clang version" in Popen([cc.split()[0], "-v"], stderr=PIPE).stderr.readline()
> >> +
> >> +# Check if CC has options, as is the case in yocto, where it uses CC="cc --sysroot..."
> >> +cc_tokens = cc.split()
> >> +if len(cc_tokens) > 1:
> >> +    cc = cc_tokens[0]
> >
> >What if someone is using `CC="cache clang"`? Then cc is set to `cache`
> >and the cc_is_clang check below will fail.
>
> Agreed, but this is a preexisting bug, let's fix this with a follow-up patch,

Ack; it is.

>
> - Arnaldo
>
>
> >
> >> +    cc_options = " ".join([str(e) for e in cc_tokens[1:]]) + " "
> >> +else:
> >> +    cc_options = ""
> >
> >> +cc_is_clang = b"clang version" in Popen([cc, "-v"], stderr=PIPE).stderr.readline()
> >>  src_feature_tests  = getenv('srctree') + '/tools/build/feature'
> >>
> >>  def clang_has_option(option):
> >> -    cc_output = Popen([cc.split()[0], str(cc.split()[1:]) + option, path.join(src_feature_tests, "test-hello.c") ], stderr=PIPE).stderr.readlines()
> >> +    cc_output = Popen([cc, cc_options + option, path.join(src_feature_tests, "test-hello.c") ], stderr=PIPE).stderr.readlines()
> >>      return [o for o in cc_output if ((b"unknown argument" in o) or (b"is not supported" in o))] == [ ]
> >>
> >>  if cc_is_clang:
> >> --
> >> 2.38.1
> >>
> >
> >



-- 
Thanks,
~Nick Desaulniers