Clang模块与std <iterator>和<boost/move/iterator.hpp>的交互
Clang模块与std <iterator>和<boost/move/iterator.hpp>的交互
提问于 2016-12-08 23:56:54
(有关我正在使用的Boost和Clang的特定版本的信息，请参阅问题的结尾)
使用新的实验性-fmodules特性在Clang /HEAD中编译下面的命令行选项，在编译以下文件时会出现一个构建错误：
#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，错误就会消失。
问题：这仅仅是Boost库(特别是Boost Move，显然)的副产品，没有为Clang模块映射文件的模块做准备吗？这是否是Clang现在为libc++实现的模块映射文件中的一个bug，或者甚至是模块实现本身中的一个bug？
有趣的是，我可以通过注释掉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来自LLVM github镜像中的主分支尖端，截至2016年12月7日(从技术上讲，它来自LLVM的一个分支，但仅在与LLVM自己的主分支相同的主分支上)：
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/binStack Overflow用户
发布于 2017-05-15 15:53:48
我现在只能代表boost 1.59.1，但它也明确地假设只有在使用clang构建时才能遇到libc++：
#if defined(__clang__) && defined(_LIBCPP_VERSION)
// ...
#else
// ...
#endif这引发了(几乎)与上述相同的错误，即使是在MacOSX10.9上也是如此，它的libc++早于libc++回归的引入，后者导致了在这个线程中讨论的问题。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/41050942
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