Patch "perf build: Remove -Wno-unused-but-set-variable from the flex flags when building with clang < 13.0.0" has been added to the 6.1-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    perf build: Remove -Wno-unused-but-set-variable from the flex flags when building with clang < 13.0.0

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-build-remove-wno-unused-but-set-variable-from-the-flex-flags-when-building-with-clang-13.0.0.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-250209-greg=kroah.com@vger.kernel.org Wed May 20 22:59:29 2026
From: Florian Fainelli <florian.fainelli@broadcom.com>
Date: Wed, 20 May 2026 09:33:20 -0700
Subject: perf build: Remove -Wno-unused-but-set-variable from the flex flags when building with clang < 13.0.0
To: stable@vger.kernel.org
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>, Adrian Hunter <adrian.hunter@intel.com>, Ian Rogers <irogers@google.com>, Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>, Florian Fainelli <florian.fainelli@broadcom.com>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, Arnaldo Carvalho de Melo <acme@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, Tom Rix <trix@redhat.com>, linux-perf-users@vger.kernel.org (open list:PERFORMANCE EVENTS SUBSYSTEM), linux-kernel@vger.kernel.org (open list:PERFORMANCE EVENTS SUBSYSTEM), bpf@vger.kernel.org (open list:BPF [MISC]), llvm@lists.linux.dev (open list:CLANG/LLVM BUILD SUPPORT), bcm-kernel-feedback-list@broadcom.com
Message-ID: <20260520163320.3073037-6-florian.fainelli@broadcom.com>

From: Arnaldo Carvalho de Melo <acme@redhat.com>

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@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/ZNUSWr52jUnVaaa%2F@kernel.org/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 tools/perf/util/Build |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -1,3 +1,6 @@
+include $(srctree)/tools/scripts/Makefile.include
+include $(srctree)/tools/scripts/utilities.mak
+
 perf-y += arm64-frame-pointer-unwind-support.o
 perf-y += annotate.o
 perf-y += block-info.o
@@ -265,15 +268,22 @@ ifeq ($(FLEX_GE_26),1)
 else
   flex_flags := -w
 endif
-CFLAGS_parse-events-flex.o  += $(flex_flags)
-CFLAGS_pmu-flex.o           += $(flex_flags)
-CFLAGS_expr-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;
 
 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))
+    flex_flags := $(subst -Wno-unused-but-set-variable,,$(flex_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 ($(BISON_GE_382),1)
   bison_flags += -Wno-switch-enum
@@ -286,6 +296,10 @@ ifeq ($(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_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)


Patches currently in stable-queue which might be from florian.fainelli@broadcom.com are

queue-6.1/perf-build-remove-wno-unused-but-set-variable-from-the-flex-flags-when-building-with-clang-13.0.0.patch
queue-6.1/perf-build-conditionally-define-ndebug.patch
queue-6.1/perf-parse-events-make-yydebug-dependent-on-doing-a-debug-build.patch
queue-6.1/perf-build-disable-fewer-bison-warnings.patch
queue-6.1/tools-build-add-3-component-logical-version-comparators.patch