linux-kernel - Re: [PATCH 1/1] perf build: Remove -Wno-unused-but-set-variable from the flex flags when building with clang

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Message-ID: <ZNY5Urywoz8trfEy@kernel.org>
Date:   Fri, 11 Aug 2023 10:36:18 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Ian Rogers <irogers@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] perf build: Remove -Wno-unused-but-set-variable from
 the flex flags when building with clang < 13.0.0

Em Thu, Aug 10, 2023 at 01:37:46PM -0300, Arnaldo Carvalho de Melo escreveu:
> clang < 13.0.0 doesn't grok -Wno-unused-but-set-variable, so just remove
> it to avoid:
> 
>   error: unknown warning option '-Wno-unused-but-set-variable'; did you mean '-Wno-unused-const-variable'? [-Werror,-Wunknown-warning-option]
>   make[4]: *** [/git/perf-6.5.0-rc4/tools/build/Makefile.build:128: /tmp/build/perf/util/pmu-flex.o] Error 1
>   make[4]: *** Waiting for unfinished jobs....
> 
> Fixes: ddc8e4c966923ad1 ("perf build: Disable fewer bison warnings")
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Ian Rogers <irogers@...gle.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Link: https://lore.kernel.org/lkml/
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

Need to do that also for the flex flags:

diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index a9051ab2d52ac926..9699e31ff4c04925 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -302,11 +302,6 @@ else
   flex_flags := -w
 endif
 
-CFLAGS_parse-events-flex.o  += $(flex_flags)
-CFLAGS_pmu-flex.o           += $(flex_flags)
-CFLAGS_expr-flex.o          += $(flex_flags)
-CFLAGS_bpf-filter-flex.o    += $(flex_flags)
-
 # Some newer clang and gcc version complain about this
 # util/parse-events-bison.c:1317:9: error: variable 'parse_events_nerrs' set but not used [-Werror,-Wunused-but-set-variable]
 #  int yynerrs = 0;
@@ -318,6 +313,7 @@ ifeq ($(CC_NO_CLANG), 0)
   CLANG_VERSION := $(shell $(CLANG) --version | head -1 | sed 's/.*clang version \([[:digit:]]\+.[[:digit:]]\+.[[:digit:]]\+\).*/\1/g')
   ifeq ($(call version-lt3,$(CLANG_VERSION),13.0.0),1)
     bison_flags := $(subst -Wno-unused-but-set-variable,,$(bison_flags))
+    flex_flags := $(subst -Wno-unused-but-set-variable,,$(flex_flags))
   endif
 endif
 
@@ -333,6 +329,11 @@ ifeq ($(BISON_LT_381),1)
   bison_flags += -DYYNOMEM=YYABORT
 endif
 
+CFLAGS_parse-events-flex.o  += $(flex_flags)
+CFLAGS_pmu-flex.o           += $(flex_flags)
+CFLAGS_expr-flex.o          += $(flex_flags)
+CFLAGS_bpf-filter-flex.o    += $(flex_flags)
+
 CFLAGS_parse-events-bison.o += $(bison_flags)
 CFLAGS_pmu-bison.o          += -DYYLTYPE_IS_TRIVIAL=0 $(bison_flags)
 CFLAGS_expr-bison.o         += -DYYLTYPE_IS_TRIVIAL=0 $(bison_flags)

> ---
>  tools/perf/util/Build | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index d487aec0b458a0d9..a9051ab2d52ac926 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -1,3 +1,4 @@
> +include $(srctree)/tools/scripts/Makefile.include
>  include $(srctree)/tools/scripts/utilities.mak
>  
>  perf-y += arm64-frame-pointer-unwind-support.o
> @@ -311,6 +312,15 @@ CFLAGS_bpf-filter-flex.o    += $(flex_flags)
>  #  int yynerrs = 0;
>  
>  bison_flags := -DYYENABLE_NLS=0 -Wno-unused-but-set-variable
> +
> +# Old clangs don't grok -Wno-unused-but-set-variable, remove it
> +ifeq ($(CC_NO_CLANG), 0)
> +  CLANG_VERSION := $(shell $(CLANG) --version | head -1 | sed 's/.*clang version \([[:digit:]]\+.[[:digit:]]\+.[[:digit:]]\+\).*/\1/g')
> +  ifeq ($(call version-lt3,$(CLANG_VERSION),13.0.0),1)
> +    bison_flags := $(subst -Wno-unused-but-set-variable,,$(bison_flags))
> +  endif
> +endif
> +
>  BISON_GE_382 := $(shell expr $(shell $(BISON) --version | grep bison | sed -e 's/.\+ \([0-9]\+\).\([0-9]\+\).\([0-9]\+\)/\1\2\3/g') \>\= 382)
>  ifeq ($(BISON_GE_382),1)
>    bison_flags += -Wno-switch-enum
> -- 
> 2.37.1
> 

-- 

- Arnaldo