Re: [PATCH 2/2] perf jevents: Enable warnings through HOSTCFLAGS

[James Clark]

On 15/10/2021 17:48, 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.

Is there any reason to not enable -Wall and -Werror so that it builds like
the main project? Or if HOSTCFLAGS ends up being the same as CORE_CFLAGS
then why not use CORE_CFLAGS instead?

I added them like this and only one unused function needs to be removed to
make it build successfully:


diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 65934984f032..b2edcedf01db 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -18,6 +18,8 @@ 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))
+HOSTCFLAGS += -Wall
+HOSTCFLAGS += -Wextra
 
 include $(srctree)/tools/scripts/Makefile.arch
 
@@ -212,6 +214,7 @@ endif
 ifneq ($(WERROR),0)
   CORE_CFLAGS += -Werror
   CXXFLAGS += -Werror
+  HOSTCFLAGS += -Werror
 endif
 
 ifndef DEBUG




> 
> Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> ---
>  tools/perf/Makefile.config  | 1 +
>  tools/perf/Makefile.perf    | 2 +-
>  tools/perf/pmu-events/Build | 2 +-
>  3 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 0ae2e3d8b832..65934984f032 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
>  
> 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 $(HOSTCFLAGS)
>  pmu-events-y	+= pmu-events.o
>  JDIR		=  pmu-events/arch/$(SRCARCH)
>  JSON		=  $(shell [ -d $(JDIR) ] &&				\
>