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

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

[Uwe Kleine-König]

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++

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.

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
-- 
2.30.2

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

[Uwe Kleine-König]

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Hello,

I picked the wrong script so the sender address was wrong. I assume I'll 
have to fix that. Will pay more attention for v2.

On 12/2/21 14:43, 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++
> 
> 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.

In the meantime I was pointed to 573cf5c9a152 ("perf build: Add missing 
-lstdc++ when linking with libopencsd"), and I wonder what I'm missing. 
Maybe my patch breaks the build if libopencsd is only available as .a?

I added the people involved in that commit to Cc: and look forward to 
details. The motivation to add -lstdc++ seems to be "It does not hurt" 
which is a bit weak.

Best regards
Uwe

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

[James Clark]

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.

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
> 

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

[Branislav Rankov]

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

[Uwe Kleine-König]

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Hello,

On 12/2/21 16:36, 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?

Yes, I have libstdc++ installed, but only the libstdc++.so.6.0.29, not 
the plain .so. The former is enough to run c++ binaries, the latter is 
only needed for linking. As none of the symbols in libstdc++ is needed 
for the kernel tools, not having the .so works fine.

>> 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.

This is a poor reasoning in my eyes. Overstating: We didn't suffer long 
enough from this problem, let's keep it around for a while.

I would hope that given the change isn't that old we have a good chance 
to find out enough details to find a good fix.

Best regards
Uwe

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

[Uwe Kleine-König]

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On 12/2/21 17:00, Branislav Rankov wrote:
> 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?

As noted in an other thread branch: I have libstdc++.so.6.0.29 but not 
libstdc++.so. For linking this is enough as the binary that is linked 
doesn't need any symbols from libstdc++.so.

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

That seems to be the path to go then.

Best regards
Uwe

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

[James Clark]

On 02/12/2021 16:07, Uwe Kleine-König wrote:
> On 12/2/21 17:00, Branislav Rankov wrote:
>> 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?
> 
> As noted in an other thread branch: I have libstdc++.so.6.0.29 but not libstdc++.so. For linking this is enough as the binary that is linked doesn't need any symbols from libstdc++.so.
> 
>> If this is a genuine problem, we could add -lstdc++ conditionally only for the
>> static build.
> 
> That seems to be the path to go then.

Hi Uwe,

Yes I think so. There are also quite a few similar cases in the makefiles like:

  ifeq ($(findstring -static,${LDFLAGS}),-static)
    DWARFLIBS += -lelf -lebl -ldl -lz -llzma -lbz2
  endif

With the conditional added to this patch:

Reviewed-by: James Clark <james.clark@arm.com>


Thanks
James

> 
> Best regards
> Uwe