macOS下g++编译HelloWorld报错：Undefined symbols for architecture x86_64

在macOS系统上编译一个简单的Hello World程序hw.cpp，代码如下：

#include <iostream>
#include <string>
using namespace std;
int main() {
  cout << "Hello world!" << endl;
  return 0;
}

使用命令g++ hw.cp编译时，收到如下错误信息：

ld: warning: ignoring file /usr/local/lib/libc++.so, building for macOS-x86_64 but attempting to link with file built for unknown-unsupported file format ( 0x49 0x4E 0x50 0x55 0x54 0x28 0x6C 0x69 0x62 0x63 0x2B 0x2B 0x2E 0x73 0x6F 0x2E )
Undefined symbols for architecture x86_64:
  "std::__1::locale::use_facet(std::__1::locale::id&) const", referenced from:
      std::__1::ctype<char> const& std::__1::use_facet<std::__1::ctype<char>>(std::__1::locale const&) in hw-a865c1.o
  "std::__1::ios_base::getloc() const", referenced from:
      std::__1::basic_ios<char, std::__1::char_traits<char>>::widen(char) const in hw-a865c1.o
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::__init(unsigned long, char)", referenced from:
      std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::basic_string(unsigned long, char) in hw-a865c1.o
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::~basic_string()", referenced from:
      std::__1::ostreambuf_iterator<char, std::__1::char_traits<char>> std::__1::__pad_and_output<char, std::__1::char_traits<char>>(std::__1::ostreambuf_iterator<char, std::__1::char_tr
...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

请问该错误产生的原因是什么？

• 文件名拼写错误：编译命令中写的是hw.cp，但实际文件名是hw.cpp，后缀名错误会导致编译器无法正确识别文件类型，后续处理逻辑异常。
• 动态库格式不兼容：警告信息显示/usr/local/lib/libc++.so文件格式不被macOS x86_64架构支持。macOS默认使用.dylib格式的动态库，而.so是Linux系统的动态库格式，该文件大概率是从其他系统移植而来，链接器无法识别，只能忽略它。
• 标准库符号缺失：由于上述libc++.so被忽略，链接器无法找到C++标准库std::__1命名空间下的核心符号（比如locale、string相关函数），最终触发“symbol(s) not found”的链接错误。

内容的提问来源于stack exchange，提问作者zachursinus