Re: [PATCH] perf: Drop -lstdc++ from OPENCSDLIBS

[Branislav Rankov <branislav.rankov@arm.com>]

On 12/2/21 15:36, James Clark wrote:
>
>
> On 02/12/2021 13:43, Uwe Kleine-König wrote:
>> From: Uwe Kleine-König <uwe@kleine-koenig.org>
>>
>> When cross compiling on amd64 for arm64 the build failed on my machine with:
>>
>>      Makefile.config:493: *** Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1.  Stop.
>>
>> even though libopencsd was installed (for both amd64 and arm64). After
>> some digging around I found the relevant error message in
>> tools/perf/feature/test-libopencsd.make.output:
>>
>>      /usr/lib/gcc-cross/aarch64-linux-gnu/11/../../../../aarch64-linux-gnu/bin/ld: cannot find -lstdc++
>
> Do you have this library installed for arm64? I know you said you had OpenCSD installed, but
> maybe the arm64 stdc++ lib is missing?
>
>>
>> Instead of fixing the error message to also include a request to install
>> libstdc++, just drop -lstdc++. With this change the build completed.
>>
>> Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
>> ---
>> Hello,
>>
>> not sure this is a pure cross compilation problem. I think in general
>> it's a bad idea to link against libstdc++ explicitly. Still more if
>> there is no C++ involved.
>
> This -lstdc++ was only just added a few months ago by Branislav so I'm
> not sure if it should be removed. OpenCSD does use C++ so it is involved,
> although I would have thought that stdc++ was a dependency of opencsd so
> it would automatically get pulled in.
>
> @Branislav, what was the build error that you were fixing with the recent
> change? I checked the commit message but it's not listed.

Hi. I was fixing the static build with this. When doing the static build you need
to list all the dependencies. I thought it would not be a problem to also list it
in the dynamic case.

I did not have problems when trying crosscompile in both dynamic and static case.
But maybe you have a case where this is a problem. I would like to understand what
your case is.
Does your libOpenCSD.so have a dependency on libstdc++.so?
If so, where is the libstdc++.so?

If this is a genuine problem, we could add -lstdc++ conditionally only for the
static build.

>
> James
>
>>
>> Best regards
>> Uwe
>>
>>  tools/perf/Makefile.config | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
>> index afd144725a0b..dc946b7a802e 100644
>> --- a/tools/perf/Makefile.config
>> +++ b/tools/perf/Makefile.config
>> @@ -143,7 +143,7 @@ FEATURE_CHECK_LDFLAGS-libcrypto = -lcrypto
>>  ifdef CSINCLUDES
>>    LIBOPENCSD_CFLAGS := -I$(CSINCLUDES)
>>  endif
>> -OPENCSDLIBS := -lopencsd_c_api -lopencsd -lstdc++
>> +OPENCSDLIBS := -lopencsd_c_api -lopencsd
>>  ifdef CSLIBS
>>    LIBOPENCSD_LDFLAGS := -L$(CSLIBS)
>>  endif
>>
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