c – Clang Modules与std和

(有关我正在使用的Boost和Clang特定版本的信息,请参阅问题末尾)

使用新的实验-fmodules功能在master / HEAD中编译Clang,使用如下所示的命令行选项编译以下文件时出现构建错误：

#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>或者在#include< boost / move / iterator.hpp>之后移动它,错误消失.

问题：这只是Boost库的副产品(Boost Move,特别是显然)没有为具有Clang模块映射文件的模块做好准备吗？这可能是Clang现在为libc实现的模块映射文件的错误,甚至是模块实现本身的错误？

有趣的是,我可以通过注释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>

正在使用的版本

提升1.61

截至2016年12月7日,Clang来自LLVM的github镜像中的主分支的尖端(技术上它来自LLVM的分支,但它只在主分支上与LLVM自己的主分支相同)：

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

解决方法

我相信这是由libc的module.modulemap问题引起的,我昨天在 r289028修复了这个问题.这个错误导致在启用模块时libc不会导出_LIBCPP_VERSION宏.

在查看boost / move / detail / iterator_traits.hpp后,似乎如果没有定义_LIBCPP_VERSION,它将错过配置并最终声明完全不同的迭代器标记定义. (具体来说,它将直接在命名空间std中定义它们,而不是在libc的版本控制命名空间中定义它们).

如果您重新构建LLVM和libc,它应该解决您的问题.如果没有自由到file a bug.

PS.看来我只是one step ahead.

c – Clang Modules与std和

解决方法

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