linux-kernel - Re: [PATCH] tools: perf: fix linker error when libelf config is disabled

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Message-ID: <5aa63b9b-1479-8dc9-d505-56a73e7fd9ee@arm.com>
Date:   Wed, 4 Jan 2017 15:45:13 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Sudeep Holla <sudeep.holla@....com>, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH] tools: perf: fix linker error when libelf config is
 disabled



On 04/01/17 14:45, Jiri Olsa wrote:
> On Wed, Jan 04, 2017 at 01:52:40PM +0000, Sudeep Holla wrote:
>> When libelf is disabled in the configuration, we get the following
>> linker error:
>>   LINK     libperf-jvmti.so
>>   ld: cannot find -lelf
>>   Makefile.perf:515: recipe for target 'libperf-jvmti.so' failed
>>
>> This patch fixes the error by using the configuration macro EXTLIBS.
>>
>> Fixes: d4dfdf00d43e ("perf jvmti: Plug compilation into perf build")
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Jiri Olsa <jolsa@...nel.org>
>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>> ---
>>  tools/perf/Makefile.perf | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
>> index 8fc24824705e..6defd9b00bc4 100644
>> --- a/tools/perf/Makefile.perf
>> +++ b/tools/perf/Makefile.perf
>> @@ -512,7 +512,7 @@ $(LIBJVMTI_IN): FORCE
>>  	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=jvmti obj=jvmti
>>  
>>  $(OUTPUT)$(LIBJVMTI): $(LIBJVMTI_IN)
>> -	$(QUIET_LINK)$(CC) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ $< -lelf -lrt
>> +	$(QUIET_LINK)$(CC) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ $< $(EXTLIBS) -lrt
>>  endif
> 
> hm, do we need -lelf -lrt at all? can't see reason for that

I agree as it links well without libelf. I was not sure if enabling
libelf has any issue removing it, hence I retained. I will remove both
and repost. Thanks for having a look.

-- 
Regards,
Sudeep