Clang Modules 与 std <iterator> 和 <boost/move/iterator.hpp 的交互>

Question

（有关Boost和Clang的特定版本的信息，请参见问题结束）

）

使用新的实验-fmodules功能在Master/Head中汇编Clang中，我从以下命令行选项中汇总了以下文件，从而获得了一个构建错误：

#include <iterator>
#include <boost/move/iterator.hpp>

编译命令和错误：

anhall@leviathan: <path-to-clang-install-from-master>/bin/clang++ -o file.o -c file.cpp --std=c++1z -stdlib=libc++ -fmodules
In file included from file.cpp:2:
In file included from /usr/local/include/boost/move/iterator.hpp:27:
/usr/local/include/boost/move/detail/iterator_traits.hpp:60:17: error: reference to 'random_access_iterator_tag' is ambiguous
   typedef std::random_access_iterator_tag   iterator_category;
                ^
/Users/anhall/impersonal/code/llvm-reflexpr/install/bin/../include/c++/v1/iterator:438:30: note: candidate found by name lookup is 'std::__1::random_access_iterator_tag'
struct _LIBCPP_TYPE_VIS_ONLY random_access_iterator_tag : public bidirectional_iterator_tag {};
                             ^
/usr/local/include/boost/move/detail/iterator_traits.hpp:34:8: note: candidate found by name lookup is 'std::random_access_iterator_tag'
struct random_access_iterator_tag;
       ^
/usr/local/include/boost/move/detail/iterator_traits.hpp:71:17: error: reference to 'random_access_iterator_tag' is ambiguous
   typedef std::random_access_iterator_tag   iterator_category;
                ^
/Users/anhall/impersonal/code/llvm-reflexpr/install/bin/../include/c++/v1/iterator:438:30: note: candidate found by name lookup is 'std::__1::random_access_iterator_tag'
struct _LIBCPP_TYPE_VIS_ONLY random_access_iterator_tag : public bidirectional_iterator_tag {};
                             ^
/usr/local/include/boost/move/detail/iterator_traits.hpp:34:8: note: candidate found by name lookup is 'std::random_access_iterator_tag'
struct random_access_iterator_tag;
       ^
In file included from file.cpp:2:
/usr/local/include/boost/move/iterator.hpp:196:17: error: reference to 'output_iterator_tag' is ambiguous
   typedef std::output_iterator_tag    iterator_category;
                ^
/Users/anhall/impersonal/code/llvm-reflexpr/install/bin/../include/c++/v1/iterator:435:30: note: candidate found by name lookup is 'std::__1::output_iterator_tag'
struct _LIBCPP_TYPE_VIS_ONLY output_iterator_tag {};
                             ^
/usr/local/include/boost/move/detail/iterator_traits.hpp:35:8: note: candidate found by name lookup is 'std::output_iterator_tag'
struct output_iterator_tag;
       ^
In file included from file.cpp:2:
/usr/local/include/boost/move/iterator.hpp:238:17: error: reference to 'output_iterator_tag' is ambiguous
   typedef std::output_iterator_tag    iterator_category;
                ^
/Users/anhall/impersonal/code/llvm-reflexpr/install/bin/../include/c++/v1/iterator:435:30: note: candidate found by name lookup is 'std::__1::output_iterator_tag'
struct _LIBCPP_TYPE_VIS_ONLY output_iterator_tag {};
                             ^
/usr/local/include/boost/move/detail/iterator_traits.hpp:35:8: note: candidate found by name lookup is 'std::output_iterator_tag'
struct output_iterator_tag;
       ^
In file included from file.cpp:2:
/usr/local/include/boost/move/iterator.hpp:278:17: error: reference to 'output_iterator_tag' is ambiguous
   typedef std::output_iterator_tag    iterator_category;
                ^
/Users/anhall/impersonal/code/llvm-reflexpr/install/bin/../include/c++/v1/iterator:435:30: note: candidate found by name lookup is 'std::__1::output_iterator_tag'
struct _LIBCPP_TYPE_VIS_ONLY output_iterator_tag {};
                             ^
/usr/local/include/boost/move/detail/iterator_traits.hpp:35:8: note: candidate found by name lookup is 'std::output_iterator_tag'
struct output_iterator_tag;
       ^
5 errors generated.

如果我删除#include <iterator>或在#include <boost/move/iterator.hpp>之后移动它，则错误消失。

问题：这仅仅是Boost库的副产品（显然，显然是Boost Move），没有为带有Clang Module Map Files的模块做好准备吗？这是模块映射文件现在已经为libc 实现的错误，甚至是模块实现的错误？

吗？

有趣的是，我可以通过评论boost/move/detail/iterator_traits.hpp的第28-28行来消除错误：

// #include <boost/move/detail/std_ns_begin.hpp>
// BOOST_MOVE_STD_NS_BEG
//
// struct input_iterator_tag;
// struct forward_iterator_tag;
// struct bidirectional_iterator_tag;
// struct random_access_iterator_tag;
// struct output_iterator_tag;
//
// BOOST_MOVE_STD_NS_END
// #include <boost/move/detail/std_ns_end.hpp>

使用中的版本

Boost 1.61

clang是从LLVM的Github镜像中的主分支的尖端，截至2016年12月7日（技术上是来自LLVM的叉子，但它仅在主分支上与LLVM自己的主人公有相同的位置）：

clang version 4.0.0 (https://github.com/matus-chochlik/clang.git b9cb1c8a1ebf52695372de12c7b04c8ef1bd8b4e) (https://github.com/llvm-mirror/llvm.git b60c7b1f61eabbe971d08568adb790a7cfc6a403)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Users/anhall/impersonal/code/llvm-reflexpr/install/bin

Answer 1

我相信这是由libc 的模块的问题引起的，我昨天在R289028中修复了该模块。此错误导致启用模块时，LIBC 不会导出_LIBCPP_VERSION宏。

查看boost/move/detail/iterator_traits.hpp后，如果未定义_LIBCPP_VERSION，它将错过配置，并最终声明迭代器标签的完全不同的定义。（具体来说，它将直接在命名空间std而不是在libc 的版本命名空间中定义它们）。

如果您重建llvm和libc ，应该解决您的问题。如果没有随意提交错误。

ps。看来我只是领先一步。

Answer 2

我目前只能以增强性1.59.1说话，但显然也可以假设只有在用clang构建时才能遇到libc ：

#if defined(__clang__) && defined(_LIBCPP_VERSION)
// ...
#else
// ...
#endif

在Mac OS X 10.9上引起了（几乎）完全相同的错误，该错误具有LIBC ，该LIBC 早于引入LIBC 回归，该回归引起了此线程中讨论的问题。