Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v2 2/2] perf jevents: Enable warnings through HOSTCFLAGS
To:     Jiri Olsa <jolsa@redhat.com>
CC:     <peterz@infradead.org>, <acme@kernel.org>, <mark.rutland@arm.com>,
        <alexander.shishkin@linux.intel.com>, <namhyung@kernel.org>,
        <mingo@redhat.com>, <irogers@google.com>,
        <linux-perf-users@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kjain@linux.ibm.com>, <james.clark@arm.com>
References: <1634807805-40093-1-git-send-email-john.garry@huawei.com>
 <1634807805-40093-3-git-send-email-john.garry@huawei.com>
 <YXFhr2YoVp9GPsDM@krava>
From:   John Garry <john.garry@huawei.com>
Message-ID: <86aee893-0b6b-bce3-d1aa-3b66365592d1@huawei.com>
Date:   Fri, 22 Oct 2021 10:42:11 +0100
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101
 Thunderbird/68.12.1
MIME-Version: 1.0
In-Reply-To: <YXFhr2YoVp9GPsDM@krava>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 21/10/2021 13:48, Jiri Olsa wrote:
>> +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))
> 

ok, so IIRC, then the rule for building .o from .c in 
tools/build/Makefile.build will pick up HOSTCFLAGS through this 
variable, so we then don't need to explicitly mention it in the 
per-target rule, so can have this as before in pmu-events/Build

HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include

right?

(Indeed I guess that we can get rid of -I$(srctree)/tools/include as well)

Thanks,
John


> 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) ] &&