在Mac OS中使用Eclipse CPP构建C项目时，我遇到了干净的构建问题 . 我已经尝试在项目属性中添加c的include目录的路径，但我仍然收到此错误 . 我的Mac OS是OS X El Capitan版本10.11.5，我的Eclipse版本是Eclipse IDE for C / C Developers，Version：Mars Release（4.5.0）和Build id：20150621-1200 .

有没有人知道什么是错的？

12:25:09 **** Incremental Build of configuration Debug for project Greetings ****
make all 
Building target: Greetings
Invoking: MacOS X C++ Linker
g++  -o "Greetings"  ./greetings.o   
Undefined symbols for architecture x86_64:
  "std::ostream::operator<<(std::ostream& (*)(std::ostream&))", referenced from:
      _main in greetings.o
  "std::ios_base::Init::Init()", referenced from:
      ___cxx_global_var_init in greetings.o
  "std::ios_base::Init::~Init()", referenced from:
      ___cxx_global_var_init in greetings.o
  "std::cout", referenced from:
      _main in greetings.o
  "std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)", referenced from:
      _main in greetings.o
  "std::basic_ostream<char, std::char_traits<char> >& std::operator<<<std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)", referenced from:
      _main in greetings.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [Greetings] Error 1

12:25:11 Build Finished (took 1s.112ms)
c++ eclipse macos