using grpc fails with linker error: file in wrong format

using grpc fails with linker error: file in wrong format

[Juergen Landwehr]

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Hi all,

I am developing a C++ library that is using gRPC.

To be able to use protoc for generating the stubs I added the following dependencies:

DEPENDS += "\
 grpc-native \ 
 protobuf-native \
 ...
 " 
and to link my library with cross-compiled libraries:

RDEPENDS += "\
grpc \
protobuf \
...
"

However, linking the library fails with the following error:

ld: /data/jenkins/workspace/e0_mbient_yocto_mbient_manifests_master_downstream/build/tmp/work/cortexa72-mbient-linux/tokenmaster-client/git-r0/recipe-sysroot-native/usr/lib/libgrpc++.so.1.24.3: error adding symbols: file in wrong format

I guess the problem is, that native grpc++ library is used from the "recipe-sysroot-native" directory and thus not the cross-compiled version.

What am I doing wrong? How can I tell Yocto to use the cross-compiled versions?

Thanks,

Jürgen

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Re: [yocto] using grpc fails with linker error: file in wrong format

[Khem Raj]

On 5/24/21 12:37 AM, Juergen Landwehr wrote:
> Hi all,
> 
> I am developing a C++ library that is using gRPC.
> 
> To be able to use protoc for generating the stubs I added the following 
> dependencies:
> 
> DEPENDS += "\
>    grpc-native \
>    protobuf-native \
>    ...
>    "
> 
> 
> and to link my library with cross-compiled libraries:
> 
> RDEPENDS += "\
>     grpc \
>     protobuf \
>     ...
>     "
> 
> However, linking the library fails with the following error:
> 
> ld: 
> /data/jenkins/workspace/e0_mbient_yocto_mbient_manifests_master_downstream/build/tmp/work/cortexa72-mbient-linux/tokenmaster-client/git-r0/recipe-sysroot-native/usr/lib/libgrpc++.so.1.24.3: 
> error adding symbols: file in wrong format
> 
> I guess the problem is, that native grpc++ library is used from the 
> "recipe-sysroot-native" directory and thus not the cross-compiled version.
> 
> What am I doing wrong? How can I tell Yocto to use the cross-compiled 
> versions?

this is upto your component's build system, so perhaps you should look 
into that and ensure that its using right options. Second place to look 
is recipe for your package and ensure right vars and options are passed 
to build. you might want to look at sysdig package build system and see 
how they are doing it and perhaps mimic that for your package too.

> 
> Thanks,
> 
> Jürgen
> 
> 
> 
> 

Re: using grpc fails with linker error: file in wrong format

[Juergen Landwehr]

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Hello Khem,

we use CMake as build system.

I checked the "sysdig" recipe and they defined both the "grpc" and "grpc-native" (same with protbuf) in the DEPENDS variable like so:

DEPENDS += "... grpc grpc-native protobuf protobuf-native ..."
If I do this in my recipe I get the following error:
*18:55:09*  -- Found Protobuf: /data/jenkins/workspace/e0_mbient_yocto_mbient_manifests_master_downstream/build/tmp/work/corei7-64-mbient-linux/tokenmaster-client/git-r0/recipe-sysroot/usr/lib/libprotobuf.so;-lpthread (found version "3.12.3") 
*18:55:09*  CMake Error at /data/jenkins/workspace/e0_mbient_yocto_mbient_manifests_master_downstream/build/tmp/work/corei7-64-mbient-linux/tokenmaster-client/git-r0/recipe-sysroot/usr/lib/cmake/grpc/gRPCTargets.cmake:197 (message):
*18:55:09*    The imported target "gRPC::grpc_cpp_plugin" references the file
*18:55:09*
*18:55:09*       "/data/jenkins/workspace/e0_mbient_yocto_mbient_manifests_master_downstream/build/tmp/work/corei7-64-mbient-linux/tokenmaster-client/git-r0/recipe-sysroot/usr/bin/grpc_cpp_plugin"
*18:55:09*
*18:55:09*    but this file does not exist.  Possible reasons include:
which is correct as the directory ".../ *recipe-sysroot* /usr/bin" does not contain any grpc plugins. However the directory ".../ *recipe-sysroot-native* /usr/bin" does (due to the dependency to grpc-native).

It seems to work for sysdig, as they do not use "find_package(Protobuf)" or "find_package("gRPC") to detect gRPC related libraries/programs but use some custom code.

So it looks like:

1) If I use "DEPENDS += "... grpc-native protobuf-native ..." I am able to generate grpc stubs and I am also able to successfully build my component, but only, if the build-host and target-host are compatible => NO CROSS COMPING
2) If I use "DEPENDS += "... grpc grpc-native protobuf protobuf-native ..." CMake immediately complains, that some the grpc plugins are missing
3) Using RDEPENDS seems to have no effect

So it seems the only way to make this work is to use "DEPENDS += grpc grpc-native ...." and write some custom CMake code to detect grpc related libraries (e.g. libgrpc++.so) and programs (e.g. protoc, grpc_cpp_plugin).

But again, I am new to Yocto and still hope, that there is an easier way?

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