Compilation finished with errors:
source.cpp: In function 'int main()':
source.cpp:36:8: warning: unused variable 'comp' [-Wunused-variable]
/tmp/cci7CfLZ.o: In function `GetComparer(std::string const&, std::string&)':
source.cpp:(.text._Z11GetComparerRKSsRSs[_Z11GetComparerRKSsRSs]+0x31): undefined reference to `GetComparer(std::string const&, std::string&)::{lambda(std::string const&, std::string const&)#1}::_FUN(std::string const&, std::string const&)'
source.cpp:(.text._Z11GetComparerRKSsRSs[_Z11GetComparerRKSsRSs]+0x6c): undefined reference to `GetComparer(std::string const&, std::string&)::{lambda(std::string const&, std::string const&)#2}::_FUN(std::string const&, std::string const&)'
source.cpp:(.text._Z11GetComparerRKSsRSs[_Z11GetComparerRKSsRSs]+0xa0): undefined reference to `GetComparer(std::string const&, std::string&)::{lambda(std::string const&, std::string const&)#3}::_FUN(std::string const&, std::string const&)'
source.cpp:(.text._Z11GetComparerRKSsRSs[_Z11GetComparerRKSsRSs]+0xd8): undefined reference to `GetComparer(std::string const&, std::string&)::{lambda(std::string const&, std::string const&)#4}::_FUN(std::string const&, std::string const&)'
collect2: error: ld returned 1 exit status