为什么这适用于 G++ 而不是 CLANG？ [关闭]

Question

正在努力学习 C/C++。

为什么在使用 g++ 而不是 clang 时这会起作用？但是当我将相同的程序转换为纯 C 并使用 gcc 和 clang...

代码：

#include <iostream>
#ifndef ARCH
#define ARCH "Undefined"
#endif

using namespace std;

int main() {
  char str[] = "Hello C++";
  cout << "Value of str is : " << str << endl;
  cout << "Value of str is : " << ARCH << endl;
  exit(0);
}

使用g++ 我运行g++ "-DARCH=\"`uname -m`\"" hello.cpp，它工作得很好。

使用clang 我运行clang "-DARCH=\"`uname -m`\"" hello.cpp，但它失败了。

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 hello-7c7087.o
  "std::__1::ios_base::getloc() const", referenced from:
      std::__1::basic_ios<char, std::__1::char_traits<char> >::widen(char) const in hello-7c7087.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 hello-7c7087.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 hello-7c7087.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::put(char)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in hello-7c7087.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in hello-7c7087.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 hello-7c7087.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 hello-7c7087.o
  "std::__1::cout", referenced from:
      _main in hello-7c7087.o
  "std::__1::ctype<char>::id", referenced from:
      std::__1::ctype<char> const& std::__1::use_facet<std::__1::ctype<char> >(std::__1::locale const&) in hello-7c7087.o
  "std::__1::locale::~locale()", referenced from:
      std::__1::basic_ios<char, std::__1::char_traits<char> >::widen(char) const in hello-7c7087.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 hello-7c7087.o
  "std::__1::ios_base::clear(unsigned int)", referenced from:
      std::__1::ios_base::setstate(unsigned int) in hello-7c7087.o
  "std::terminate()", referenced from:
      ___clang_call_terminate in hello-7c7087.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 hello-7c7087.o
      ___clang_call_terminate in hello-7c7087.o
  "___cxa_call_unexpected", referenced from:
      std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >::ostreambuf_iterator(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in hello-7c7087.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 hello-7c7087.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 hello-7c7087.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 hello-7c7087.o
      std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >::ostreambuf_iterator(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in hello-7c7087.o
      std::__1::basic_ios<char, std::__1::char_traits<char> >::widen(char) const in hello-7c7087.o
      Dwarf Exception Unwind Info (__eh_frame) in hello-7c7087.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

对我来说真正没有意义的是，如果我将代码转换为 C，它会双向工作。

提前致谢！

Answer 1

您似乎正在使用clang 编译C++ 代码。你应该使用clang++ 来编译它

您可能还想使用-Wall 和-Werror 来捕捉许多在其他语言中可能是错误的东西（例如：在具有 int 返回类型的函数中不返回任何内容）。

我个人用以下编译。我不确定 sanitize 是否适用于 Windows。 no-exceptions 和 no-rtti 很常见，但不是大多数人所做的。如果你使用这些，你会遇到一些 dynamic_cast 和异常的错误。

clang++ -g -fsanitize=undefined -fno-exceptions -fno-rtti -Wall -Wpedantic -Wextra myfile.cpp