Problem:
When trying to compile your C++ application, you see lots of undefined reference to messages like
AutoBenchmark.cpp:(.text+0x6a): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x81): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x8a): undefined reference to `std::chrono::_V2::system_clock::now()' /usr/bin/ld: AutoBenchmark.cpp:(.text+0xcd): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()' /usr/bin/ld: AutoBenchmark.cpp:(.text+0xe6): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()' /usr/bin/ld: /tmp/cc356AdP.o: in function `AutoBenchmark::~AutoBenchmark()': AutoBenchmark.cpp:(.text+0x17e): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x18e): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()' /usr/bin/ld: /tmp/cc356AdP.o: in function `AutoBenchmark::Record(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)': AutoBenchmark.cpp:(.text+0x1db): undefined reference to `std::chrono::_V2::system_clock::now()' /usr/bin/ld: /tmp/cc356AdP.o: in function `AutoBenchmark::Record(char const*)': AutoBenchmark.cpp:(.text+0x252): undefined reference to `std::allocator<char>::allocator()' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x288): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x294): undefined reference to `std::allocator<char>::~allocator()' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x2b9): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x2ce): undefined reference to `std::allocator<char>::~allocator()' /usr/bin/ld: /tmp/cc356AdP.o: in function `AutoBenchmark::Print()': AutoBenchmark.cpp:(.text+0x316): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::length() const' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x332): undefined reference to `std::cout' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x337): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x344): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x572): undefined reference to `std::cout' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x577): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x59c): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x5ab): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x5c2): undefined reference to `std::ostream::operator<<(double)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x5d1): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x607): undefined reference to `std::cout' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x60c): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x631): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x640): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x657): undefined reference to `std::ostream::operator<<(double)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x666): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x69c): undefined reference to `std::cout' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x6a1): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x6c6): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x6d5): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x6ec): undefined reference to `std::ostream::operator<<(double)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x6fb): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x731): undefined reference to `std::cout' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x736): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x75b): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x76a): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x781): undefined reference to `std::ostream::operator<<(double)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x790): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)' /usr/bin/ld: AutoBenchmark.cpp:(.text+0x7c6): undefined reference to `std::cout'
Solution:
You need to link the stdc++ library by adding -lstdc++ to your compiler/linker flags.
For example, instead of
gcc -o myprogram *.c
use
gcc -o myprogram *.c -lstdc++