xcode编译出错：Undefined symbols for architecture armv7

在xcode中编译oc和c++代码时出现如下错误：

Undefined symbols for architecture armv7
"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::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)"
"std::string::c_str() const", referenced from:
.....

基本可以断定是缺少libstdc++.6.0.9.dylib库引起的。

在Xcode中导入库就行，如图