Question

在Stroustrup的PPP中这是一个非常简单的练习，你可以创建3个文件：

my.h：

void print_foo();
void print(int);

my.cpp：

#include <iostream>
#include <string>
#include "my.h"

using namespace std;

void print(int i)
{
    cout << i << '\n';
}

void print_foo()
{
    cout << "Foo" << '\n';
}

和use.cpp：

#include "my.h"

int main()
{
    print_foo();
    print(7);
}

我的铿锵声版本为Apple LLVM version 7.0.2 (clang-700.1.81) Target: x86_64-apple-darwin15.2.0

这在clang和g ++中都有编译，但在clang中没有链接。我明白了：

$ clang my.cpp use.cpp -std=c++14 -o drill8_1
Undefined symbols for architecture x86_64:

有谁知道为什么会这样？我在g ++中键入了相同的命令，得到了正确的输出。

谢谢：）

这是clang输出的其余部分：

    Undefined symbols for architecture x86_64:
  "std::__1::locale::use_facet(std::__1::locale::id&) const", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::__1::ios_base::getloc() const", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(unsigned long, char)", 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_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in my-82a25e.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_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in my-82a25e.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::sentry(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::~sentry()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(int)", referenced from:
      print(int) in my-82a25e.o
  "std::__1::cout", referenced from:
      print(int) in my-82a25e.o
      print_foo() in my-82a25e.o
  "std::__1::ctype<char>::id", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::__1::locale::~locale()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::__1::ios_base::__set_badbit_and_consider_rethrow()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::__1::ios_base::clear(unsigned int)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "std::terminate()", referenced from:
      ___clang_call_terminate in my-82a25e.o
  "___cxa_begin_catch", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
      ___clang_call_terminate in my-82a25e.o
  "___cxa_end_catch", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
  "___gxx_personality_v0", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in my-82a25e.o
      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_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in my-82a25e.o
      Dwarf Exception Unwind Info (__eh_frame) in my-82a25e.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

无法与clang链接，因为clang旨在用作C编译器。这个传统 - 如果你可以称之为 - 来自GCC，其命令行界面clang紧随其后。如果您将GCC调用为g++或将Clang调用为clang++，它将自动理解它是编译C ++代码，它将自动链接到C ++标准库中。

如果您使用普通gcc或clang，您仍然可以编译C ++代码，但要链接它，您通常需要明确链接标准库（例如-lc++。它更容易更常见的是在调用编译器时只使用面向C ++的名称。

我的（简单）代码链接用g ++编写，不会在clang

1 个答案: