linux-kernel - Re: [PATCH v2 2/2] perf jevents: Enable warnings through HOSTCFLAGS

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Message-ID: <YXFhr2YoVp9GPsDM@krava>
Date:   Thu, 21 Oct 2021 14:48:47 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     John Garry <john.garry@...wei.com>
Cc:     peterz@...radead.org, acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        mingo@...hat.com, irogers@...gle.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        kjain@...ux.ibm.com, james.clark@....com
Subject: Re: [PATCH v2 2/2] perf jevents: Enable warnings through HOSTCFLAGS

On Thu, Oct 21, 2021 at 05:16:45PM +0800, John Garry wrote:
> Currently no compiler warnings at all are enabled for building jevents,
> so help catch bugs at compile time by enabling through HOSTCFLAGS.
> 
> Signed-off-by: John Garry <john.garry@...wei.com>
> ---
>  tools/perf/Makefile.config  | 5 +++++
>  tools/perf/Makefile.perf    | 2 +-
>  tools/perf/pmu-events/Build | 2 +-
>  3 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 0ae2e3d8b832..374f65b52157 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -17,6 +17,7 @@ detected     = $(shell echo "$(1)=y"       >> $(OUTPUT).config-detected)
>  detected_var = $(shell echo "$(1)=$($(1))" >> $(OUTPUT).config-detected)
>  
>  CFLAGS := $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
> +HOSTCFLAGS := $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
>  
>  include $(srctree)/tools/scripts/Makefile.arch
>  
> @@ -211,6 +212,7 @@ endif
>  ifneq ($(WERROR),0)
>    CORE_CFLAGS += -Werror
>    CXXFLAGS += -Werror
> +  HOSTCFLAGS += -Werror
>  endif
>  
>  ifndef DEBUG
> @@ -292,6 +294,9 @@ CXXFLAGS += -ggdb3
>  CXXFLAGS += -funwind-tables
>  CXXFLAGS += -Wno-strict-aliasing
>  
> +HOSTCFLAGS += -Wall
> +HOSTCFLAGS += -Wextra
> +
>  # Enforce a non-executable stack, as we may regress (again) in the future by
>  # adding assembler files missing the .GNU-stack linker note.
>  LDFLAGS += -Wl,-z,noexecstack
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 7df13e74450c..118bcdc70bb4 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -226,7 +226,7 @@ else
>  endif
>  
>  export srctree OUTPUT RM CC CXX LD AR CFLAGS CXXFLAGS V BISON FLEX AWK
> -export HOSTCC HOSTLD HOSTAR
> +export HOSTCC HOSTLD HOSTAR HOSTCFLAGS
>  
>  include $(srctree)/tools/build/Makefile.include
>  
> diff --git a/tools/perf/pmu-events/Build b/tools/perf/pmu-events/Build
> index a055dee6a46a..d5c287f069a2 100644
> --- a/tools/perf/pmu-events/Build
> +++ b/tools/perf/pmu-events/Build
> @@ -1,7 +1,7 @@
>  hostprogs := jevents
>  
>  jevents-y	+= json.o jsmn.o jevents.o
> -HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include
> +HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include $(HOSTCFLAGS)

so the the host cflags are made of:

host_c_flags = -Wp,-MD,$(depfile) -Wp,-MT,$@ $(KBUILD_HOSTCFLAGS) -D"BUILD_STR(s)=\#s" $(HOSTCFLAGS_$(basetarget).o) $(HOSTCFLAGS_$(obj))

can't you use KBUILD_HOSTCFLAGS?

also perhaps we could rename KBUILD_HOSTCFLAGS to HOSTCFLAGS?
the name seems like leftover from kbuild move

jirka

>  pmu-events-y	+= pmu-events.o
>  JDIR		=  pmu-events/arch/$(SRCARCH)
>  JSON		=  $(shell [ -d $(JDIR) ] &&				\
> -- 
> 2.17.1
>