linux-kernel - Re: [PATCH v1 4/6] perf build: Disable fewer flex warnings

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Message-ID: <ZMQMQoCtBytgwB4i@kernel.org>
Date:   Fri, 28 Jul 2023 15:43:14 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     James Clark <james.clark@....com>,
        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>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Eduard Zingerman <eddyz87@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Gaosheng Cui <cuigaosheng1@...wei.com>,
        Rob Herring <robh@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v1 4/6] perf build: Disable fewer flex warnings

Em Fri, Jul 28, 2023 at 03:10:05PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Jul 28, 2023 at 08:26:54AM -0700, Ian Rogers escreveu:
> > On Fri, Jul 28, 2023 at 7:02 AM Arnaldo Carvalho de Melo
> > > I added this to the patch to get it moving:
> > >
> > > make: Leaving directory '/var/home/acme/git/perf-tools-next/tools/perf'
> > > ⬢[acme@...lbox perf-tools-next]$ git diff
> > > diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> > > index 32239c4b0393c319..afa93eff495811cf 100644
> > > --- a/tools/perf/util/Build
> > > +++ b/tools/perf/util/Build
> > > @@ -281,7 +281,7 @@ $(OUTPUT)util/bpf-filter-bison.c $(OUTPUT)util/bpf-filter-bison.h: util/bpf-filt
> > >
> > >  FLEX_GE_264 := $(shell expr $(shell $(FLEX) --version | sed -e  's/flex \([0-9]\+\).\([0-9]\+\).\([0-9]\+\)/\1\2\3/g') \>\= 264)
> > >  ifeq ($(FLEX_GE_264),1)
> > > -  flex_flags := -Wno-redundant-decls -Wno-switch-default -Wno-unused-function
> > > +  flex_flags := -Wno-redundant-decls -Wno-switch-default -Wno-unused-function -Wno-misleading-indentation
> > >  else
> > >    flex_flags := -w
> > >  endif
> > > ⬢[acme@...lbox perf-tools-next]$
> > >
> > >
> > > > 1 error generated.
> > > > make[4]: *** [/var/home/acme/git/perf-tools-next/tools/build/Makefile.build:97: util/parse-events-flex.o] Error 1
> > > > make[4]: *** Waiting for unfinished jobs....
> > > >   LD      util/scripting-engines/perf-in.o
> > > > make[3]: *** [/var/home/acme/git/perf-tools-next/tools/build/Makefile.build:140: util] Error 2
> > > > make[2]: *** [Makefile.perf:682: perf-in.o] Error 2
> > > > make[2]: *** Waiting for unfinished jobs....
> > > >   CC      pmu-events/pmu-events.o
> > > >   LD      pmu-events/pmu-events-in.o
> > > > make[1]: *** [Makefile.perf:242: sub-make] Error 2
> > > > make: *** [Makefile:70: all] Error 2
> > > >
> > > > ⬢[acme@...lbox perf-tools-next]$ clang --version
> > > > clang version 14.0.5 (Fedora 14.0.5-2.fc36)
> > > > Target: x86_64-redhat-linux-gnu
> > > > Thread model: posix
> > > > InstalledDir: /usr/bin
> > > > ⬢[acme@...lbox perf-tools-next]$
> > 
> > Thanks James/Arnaldo, I was trying to be aggressive in having more
> > flags, but it seems too aggressive. We should probably bring back the
> > logic to make this flag only added if it is supported:
> >   CC_HASNT_MISLEADING_INDENTATION := $(shell echo "int main(void) {
> > return 0 }" | $(CC) -Werror -Wno-misleading-indentation -o /dev/null
> > -xc - 2>&1 | grep -q -- -Wno-misleading-indentation ; echo $$?)
> >   ifeq ($(CC_HASNT_MISLEADING_INDENTATION), 1)
> >     flex_flags += -Wno-misleading-indentation
> >   endif
> > Arnaldo, is the misleading indentation in the bison generated code or
> > something copy-pasted from the parse-events.l ? If the latter we may
> > be able to fix the .l file to keep the warning.
> 
> I haven't checked, lemme do it now.

It comes directly from flex's m4 files:

https://github.com/westes/flex/blob/master/src/c99-flex.skl#L2044

So I'll keep the -Wno-misleading-indentation, ok?

- Arnaldo