Clang无法再使用<functional>标头编译程序

Question

我在clang运行ArchLinux的系统上使用版本4.0.0,它总是工作正常,但最近我无法编译使用某些STL头文件的程序!

细节:

产量clang --version:

 clang version 4.0.0 (tags/RELEASE_400/final)
 Target: x86_64-unknown-linux-gnu
 Thread model: posix
 InstalledDir: /usr/bin

产量gcc --version:

 gcc (GCC) 7.1.1 20170528

例:

我尝试编译以下简单的程序:

#include <functional>

int main()
{
    return 0;
}

我使用以下命令:

clang++ -std=c++1z test.cxx

结果就是失败:

In file included from test.cxx:3:
In file included from /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/functional:60:
In file included from /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/unordered_map:47:
In file included from /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/bits/hashtable.h:37:
In file included from /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/bits/node_handle.h:39:
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/optional:1032:27: error: use of
      class template 'optional' requires template arguments
  template <typename _Tp> optional(_Tp) -> optional<_Tp>;
                          ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/optional:451:11: note: template
      is declared here
    class optional
          ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/optional:1032:40: error: 
      expected ';' at end of declaration
  template <typename _Tp> optional(_Tp) -> optional<_Tp>;
                                       ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.1.1/../../../../include/c++/7.1.1/optional:1032:41: error: cannot
      use arrow operator on a type
  template <typename _Tp> optional(_Tp) -> optional<_Tp>;
                                        ^
3 errors generated.

这是STL中的错误还是我的设置搞砸了？

Answer 1

你的设置搞砸了.有趣的是,我有完全相同的问题.

当您升级到gcc 7.1.1时,libstdc ++(它是gcc的标准库)与它一起更新,以提供C++ 17的新功能.使用gcc,这是有效的,因为它几乎完全支持C++ 17.

但是铿锵没有.提示是-std=c++1z标志而不是gcc的-std=c++17标志.Clang缺少演绎指南,当它在libstdc ++中遇到它们时,它不知道如何处理它们.

您可以从ALA安装旧的libstdc ++包,也可以下载/使用LLVM的标准库libc ++,它自然只具有部分C++ 17功能.