Compilation error

CMakeFiles/run_mapping_offline.dir/run_mapping_offline.cc.o: In function `__static_initialization_and_destruction_0':
/home/wong/workspace_demo/packagetest_faster_lio_ws/src/***/***/app/run_mapping_offline.cc:16: undefined reference to `google::FlagRegisterer::FlagRegisterer<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >(char const*, char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*)'
/home/wong/workspace_demo/packagetest_faster_lio_ws/src/***/***/app/run_mapping_offline.cc:17: undefined reference to `google::FlagRegisterer::FlagRegisterer<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >(char const*, char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*)'
/home/wong/workspace_demo/***/src/***/***/app/run_mapping_offline.cc:18: undefined reference to `google::FlagRegisterer::FlagRegisterer<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >(char const*, char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*)'
/home/wong/workspace_demo/***/src/***/***/app/run_mapping_offline.cc:19: undefined reference to `google::FlagRegisterer::FlagRegisterer<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >(char const*, char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*)'
collect2: error: ld returned 1 exit status
***/***/app/CMakeFiles/run_mapping_offline.dir/build.make:678: recipe for target '/home/wong/workspace_demo/***/devel/lib/faster_lio/run_mapping_offline' failed

2. Solution

Add the following line in CMakeLists.txt:

find_package(gflags REQUIRED)

This is our own solution. If you have any other better solutions, please leave a comment and let me know.