问题描述

在(尝试)升级 VS2012 项目以使用 boost 1.57 之后，我无法再编译——来自 boost/any_iterator.hpp(见下文)的大量错误消息.作为测试，我创建了一个新项目，它只包含一个空的 main 函数和 #include "boost/any_iterator.hpp" 并得到了相同的错误集.这是它抱怨的代码:

After (attempting to) upgrade a VS2012 project to use boost 1.57, I can no longer compile--lots and lots of error messages coming out of boost/any_iterator.hpp (see below). As a test, I created a new project that contained nothing but an empty main function and #include "boost/any_iterator.hpp" and got the same set of errors. Here is the code it's complaining about:

// snippet from boost/any_iterator.hpp

template<
            class Value
          , class Traversal
          , class Reference
          , class Difference
          , class Buffer
        >
        class postfix_increment_proxy<
                    range_detail::any_iterator< // line 131
                        Value
                      , Traversal
                      , Reference
                      , Difference
                      , Buffer
                    >
                >
        {
            // ...
        };

在同一个文件中有另一个类遵循相同的模式并产生相同的错误.range_detail::any_iterator 在文件中向前声明了一点:

There is another class in the same file that follows the same pattern and generates identical errors. range_detail::any_iterator is forward-declared a little higher up in the file:

namespace range_detail
{
   // ...
   template<
                class Value
              , class Traversal
              , class Reference
              , class Difference
              , class Buffer = any_iterator_default_buffer
            >
            class any_iterator;
    // ...
}

就其价值而言，这是我从 VS2012 得到的一组错误:

For what it's worth, here's the set of errors I get from VS2012:

Error   1   error C2143: syntax error : missing ';' before '<'  [path]oost
angedetailany_iterator.hpp  131
Error   2   error C2059: syntax error : '<' [path]oost
angedetailany_iterator.hpp  131
Error   3   error C2065: 'Value' : undeclared identifier    [path]oost
angedetailany_iterator.hpp  134
Error   4   error C2065: 'Traversal' : undeclared identifier    [path]oost
angedetailany_iterator.hpp  135
Error   5   error C2065: 'Reference' : undeclared identifier    [path]oost
angedetailany_iterator.hpp  136
Error   6   error C2065: 'Difference' : undeclared identifier   [path]oost
angedetailany_iterator.hpp  137
Error   7   error C2065: 'Buffer' : undeclared identifier   [path]oost
angedetailany_iterator.hpp  138
Error   8   error C2923: 'boost::range_detail::any_iterator' : 'Value' is not a valid template type argument for parameter 'Value'  [path]oost
angedetailany_iterator.hpp  138
Error   9   error C2923: 'boost::range_detail::any_iterator' : 'Traversal' is not a valid template type argument for parameter 'Traversal'  [path]oost
angedetailany_iterator.hpp  138
Error   10  error C2923: 'boost::range_detail::any_iterator' : 'Reference' is not a valid template type argument for parameter 'Reference'  [path]oost
angedetailany_iterator.hpp  138
Error   11  error C2923: 'boost::range_detail::any_iterator' : 'Difference' is not a valid template type argument for parameter 'Difference'    [path]oost
angedetailany_iterator.hpp  138
Error   12  error C2923: 'boost::range_detail::any_iterator' : 'Buffer' is not a valid template type argument for parameter 'Buffer'    [path]oost
angedetailany_iterator.hpp  138
Error   13  error C2143: syntax error : missing ';' before '{'  [path]oost
angedetailany_iterator.hpp  140
Error   14  error C2447: '{' : missing function header (old-style formal list?) [path]oost
angedetailany_iterator.hpp  140

有人知道解决方法吗?

推荐答案

这似乎是 boost 代码库中的一个错误.postfix_increment_proxy 和 writable_postfix_increment_proxy 都在 boost::iterators::detail 命名空间 (iterator_facade.hpp) 中.但是，这两个名称在 any_iterator.hpp 中都未限定使用.在两个名称前添加 boost::iterators::detail:: 允许代码编译.

This appears to be a bug in the boost codebase. postfix_increment_proxy and writable_postfix_increment_proxy are both in the boost::iterators::detail namespace (iterator_facade.hpp). However, both names are used unqualified in any_iterator.hpp. Adding boost::iterators::detail:: in front of both names allows the code to compile.

对于那些对编辑 boost 代码的想法感到不舒服的人，包括 iterator_facade.hpp 后跟 using namespace boost::iterators::detail 后跟 any_iterator.hpp 的包含也可以解决问题以命名空间污染为代价.VS2012 不支持它们，所以它对我没有任何好处，但你大概也可以使用 C++11.

For anyone who's uncomfortable with the idea of editing boost code, including iterator_facade.hpp followed by using namespace boost::iterators::detail followed by an include for any_iterator.hpp will also solve the problem at the cost of namespace pollution. VS2012 doesn't support them so it doesn't do me any good, but you could presumably use a C++11 using too.

提交的工单:https://svn.boost.org/trac/boost/ticket/10754

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