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

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Message-ID: <a8833945-3f0a-7651-39ff-a01e7edc2b3a@arm.com>
Date:   Fri, 28 Jul 2023 09:50:59 +0100
From:   James Clark <james.clark@....com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        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



On 28/07/2023 07:49, Ian Rogers wrote:
> If flex is version 2.6.4, reduce the number of flex C warnings
> disabled. Earlier flex versions have all C warnings disabled.

Hi Ian,

I get a build error with either this one or the bison warning change:

  $ make LLVM=1 -C tools/perf NO_BPF_SKEL=1 DEBUG=1

  util/pmu-bison.c:855:9: error: variable 'perf_pmu_nerrs' set but not
used [-Werror,-Wunused-but-set-variable]
    int yynerrs = 0;

I tried a clean build which normally fixes these kind of bison errors.
Let me know if you need any version info.

James

> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/Build | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 96f4ea1d45c5..32239c4b0393 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -279,13 +279,9 @@ $(OUTPUT)util/bpf-filter-bison.c $(OUTPUT)util/bpf-filter-bison.h: util/bpf-filt
>  	$(Q)$(call echo-cmd,bison)$(BISON) -v $< -d $(PARSER_DEBUG_BISON) $(BISON_FILE_PREFIX_MAP) \
>  		-o $(OUTPUT)util/bpf-filter-bison.c -p perf_bpf_filter_
>  
> -FLEX_GE_26 := $(shell expr $(shell $(FLEX) --version | sed -e  's/flex \([0-9]\+\).\([0-9]\+\)/\1\2/g') \>\= 26)
> -ifeq ($(FLEX_GE_26),1)
> -  flex_flags := -Wno-switch-enum -Wno-switch-default -Wno-unused-function -Wno-redundant-decls -Wno-sign-compare -Wno-unused-parameter -Wno-missing-prototypes -Wno-missing-declarations
> -  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
> +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
>  else
>    flex_flags := -w
>  endif