During build, undefined references to protobuf

[MyGithubNotYours]

I'm trying to build ign-gazebo, but it looks like I'm having trouble with protobuf. At first, the ign-gazebo building was giving me this error:

• error: google/protobuf/port_def.inc: No such file or directory
• using protobuf 3.6 from apt-get install protobuf

I figured that maybe protobuf 3.6 was too old, so I switched to the newest version - protobuf v3.20. Now, I'm getting these errors about Print. What's the solution?

From CMakeLists.txt in ign-msgs: --> PROTOBUF LIB: /usr/local/lib/libprotobuf.a;-lpthread --> PROTOBUF INCLUDE: /usr/local/include --> PROTOBUF VERSION: 3.20.1 --> PROTOBUF Found: TRUE

$ colcon build --merge-install --cmake-clean-cache 
Starting >>> ignition-cmake3
Starting >>> ignition-tools2
Finished <<< ignition-tools2 [0.67s]                                                            
Finished <<< ignition-cmake3 [0.72s]                   
Starting >>> ignition-utils2
Finished <<< ignition-utils2 [2.70s]                     
Starting >>> ignition-math7
Finished <<< ignition-math7 [3.71s]                      
Starting >>> ignition-common5
Starting >>> ignition-msgs9
--- stderr: ignition-msgs9                                                                          

/usr/bin/ld: CMakeFiles/ign_msgs_gen.dir/Generator.cc.o: in function `google::protobuf::compiler::cpp::Generator::Generate(google::protobuf::FileDescriptor const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, google::protobuf::compiler::GeneratorContext*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*) const':
/home/--/workspace-ign-gazebo/ign-msgs/src/Generator.cc:91: undefined reference to `google::protobuf::io::Printer::Print(char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: /home/--/workspace-ign-gazebo/ign-msgs/src/Generator.cc:92: undefined reference to `google::protobuf::io::Printer::Print(char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: /home/--/workspace-ign-gazebo/ign-msgs/src/Generator.cc:93: undefined reference to `google::protobuf::io::Printer::Print(char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: /home/--/workspace-ign-gazebo/ign-msgs/src/Generator.cc:94: undefined reference to `google::protobuf::io::Printer::Print(char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: /home/--/workspace-ign-gazebo/ign-msgs/src/Generator.cc:95: undefined reference to `google::protobuf::io::Printer::Print(char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/bin/ld: CMakeFiles/ign_msgs_gen.dir/Generator.cc.o:/home/--/workspace-ign-gazebo/ign-msgs/src/Generator.cc:97: more undefined references to `google::protobuf::io::Printer::Print(char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' follow
collect2: error: ld returned 1 exit status
gmake[2]: *** [src/CMakeFiles/ign_msgs_gen.dir/build.make:101: bin/ign_msgs_gen] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:1236: src/CMakeFiles/ign_msgs_gen.dir/all] Error 2
gmake: *** [Makefile:163: all] Error 2
---
Failed   <<< ignition-msgs9 [3.13s, exited with code 2]
Aborted  <<< ignition-common5 [3.64s]                             

Summary: 4 packages finished [10.9s]
  1 package failed: ignition-msgs9
  1 package aborted: ignition-common5
  1 package had stderr output: ignition-msgs9
  10 packages not processed

[chapulina]

I see you're compiling Garden. That will be officially supported on Ubuntu Focal and Jammy. They have protobuf versions 3.6.1 and 3.12.4 respectively.

We're willing to accept pull requests improving support for 3.20, as long as that doesn't break the lower versions.

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[chapulina]

I should also mention that the issue you're seeing is coming from the messages library, not this repository.

https://github.com/ignitionrobotics/ign-msgs/