Boost MSM状态机超50转换：扩展mpl::vector至60的实现疑问

背景 #

Boost MSM状态机的转换表基于mpl::vector实现时，默认最大容量为20。通过定义以下宏可将上限提升至50：

#define BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
#define BOOST_MPL_LIMIT_VECTOR_SIZE 50                
#define BOOST_MPL_LIMIT_MAP_SIZE 50 

要进一步扩展至60，需添加mpl/vector60.hpp和mpl/map60.hpp文件。现有boost/mpl/vector目录下存在vector50.hpp和vector50_c.hpp，其中vector50.hpp内容如下：

#ifndef BOOST_MPL_VECTOR_VECTOR50_HPP_INCLUDED
#define BOOST_MPL_VECTOR_VECTOR50_HPP_INCLUDED

// Copyright Aleksey Gurtovoy 2000-2004
//
// Distributed under the Boost Software License, Version 1.0. 
// (See accompanying file LICENSE_1_0.txt or copy at 
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/mpl for documentation.

// $Id$
// $Date$
// $Revision$

#if !defined(BOOST_MPL_PREPROCESSED_HEADERS)
#   include <boost/mpl/vector/vector40.hpp>
#endif

#include <boost/mpl/aux_/config/use_preprocessed.hpp>

#if !defined(BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS) \
    && !defined(BOOST_MPL_PREPROCESSING_MODE)

#   define BOOST_MPL_PREPROCESSED_HEADER vector50.hpp
#   include <boost/mpl/vector/aux_/include_preprocessed.hpp>

#else

#   include <boost/mpl/aux_/config/typeof.hpp>
#   include <boost/mpl/aux_/config/ctps.hpp>
#   include <boost/preprocessor/iterate.hpp>

namespace boost { namespace mpl {

#   define BOOST_PP_ITERATION_PARAMS_1 \
    (3,(41, 50, <boost/mpl/vector/aux_/numbered.hpp>))
#   include BOOST_PP_ITERATE()

}}

#endif // BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS

#endif // BOOST_MPL_VECTOR_VECTOR50_HPP_INCLUDED

疑问 #

1. 是否需要同时添加vector60.hpp和vector60_c.hpp？二者区别是什么？
2. 这些文件应放置在哪个目录下？是否为boost/mpl/vector？
3. 如何修改文件内容？

尝试与错误 #

我自行编写了vector60.hpp初稿：

#ifndef BOOST_MPL_VECTOR_VECTOR60_HPP_INCLUDED
#define BOOST_MPL_VECTOR_VECTOR60_HPP_INCLUDED

// Copyright Aleksey Gurtovoy 2000-2004
//
// Distributed under the Boost Software License, Version 1.0. 
// (See accompanying file LICENSE_1_0.txt or copy at 
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/mpl for documentation.

// $Id$
// $Date$
// $Revision$

#if !defined(BOOST_MPL_PREPROCESSING_MODE)
#   include <boost/mpl/vector/vector50.hpp>
#endif

#include <boost/mpl/aux_/config/use_preprocessed.hpp>

#if !defined(BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS) \
    && !defined(BOOST_MPL_PREPROCESSING_MODE)

#   define BOOST_MPL_PREPROCESSED_HEADER vector60.hpp
#   include <boost/mpl/vector/aux_/include_preprocessed.hpp>

#else

#   include <boost/mpl/aux_/config/typeof.hpp>
#   include <boost/mpl/aux_/config/ctps.hpp>
#   include <boost/preprocessor/iterate.hpp>

namespace boost { namespace mpl {

#   define BOOST_PP_ITERATION_PARAMS_1 \
    (3,(51, 60, <boost/mpl/vector/aux_/numbered.hpp>))
#   include BOOST_PP_ITERATE()

}}

#endif // BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS

#endif // BOOST_MPL_VECTOR_VECTOR60_HPP_INCLUDED

但运行以下测试代码时：

#define BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
#define BOOST_MPL_LIMIT_VECTOR_SIZE 60
#include <boost/mpl/vector.hpp>

int main() {

    typedef boost::mpl::vector<
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int,
                int
            > vector_51;

    return 0;
}

出现编译错误：

/usr/include/boost/mpl/vector.hpp:36:1: fatal error: boost/mpl/vector/vector60.hpp: No such file or directory
   36 | #   include BOOST_PP_STRINGIZE(boost/mpl/vector/AUX778076_VECTOR_HEADER)

我偏好通过在包含头文件前添加代码实现编译时生成的方案，但目前先实现自定义文件让测试代码运行即可。

解答 #

1. 是否需要同时添加vector60.hpp和vector60_c.hpp？二者区别是什么？ #

• 若仅使用mpl::vector（存储任意C++类型的容器），仅需添加vector60.hpp；若使用mpl::vector_c（存储同类型整数常量的容器，如vector_c<int, 1,2,3>），则需同时添加vector60_c.hpp。
• 核心区别：vector.hpp系列是类型容器，用于存放任意C++类型；vector_c.hpp系列是整数常量容器，基于integral_c实现，专门用于管理同类型整数常量集合。

2. 文件放置目录 #

是的，必须将vector60.hpp和vector60_c.hpp放在boost/mpl/vector/目录下，与vector50.hpp、vector50_c.hpp同目录。本次编译错误的直接原因就是文件未放置在正确路径。

3. 文件内容修改 #

（1）vector60.hpp的正确内容

你编写的初稿已基本正确，无需额外修改：

• 前置头文件引用vector50.hpp正确
• 预处理器迭代范围(51, 60, ...)正确
• 预编译头定义BOOST_MPL_PREPROCESSED_HEADER设为vector60.hpp正确

（2）vector60_c.hpp的编写（若需要）

参照vector50_c.hpp结构，复制后修改关键部分：

#ifndef BOOST_MPL_VECTOR_VECTOR60_C_HPP_INCLUDED
#define BOOST_MPL_VECTOR_VECTOR60_C_HPP_INCLUDED

// Copyright Aleksey Gurtovoy 2000-2004
//
// Distributed under the Boost Software License, Version 1.0. 
// (See accompanying file LICENSE_1_0.txt or copy at 
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/mpl for documentation.

// $Id$
// $Date$
// $Revision$

#if !defined(BOOST_MPL_PREPROCESSING_MODE)
#   include <boost/mpl/vector/vector50_c.hpp>
#endif

#include <boost/mpl/aux_/config/use_preprocessed.hpp>

#if !defined(BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS) \
    && !defined(BOOST_MPL_PREPROCESSING_MODE)

#   define BOOST_MPL_PREPROCESSED_HEADER vector60_c.hpp
#   include <boost/mpl/vector/aux_/include_preprocessed.hpp>

#else

#   include <boost/mpl/aux_/config/typeof.hpp>
#   include <boost/mpl/aux_/config/ctps.hpp>
#   include <boost/preprocessor/iterate.hpp>

namespace boost { namespace mpl {

#   define BOOST_PP_ITERATION_PARAMS_1 \
    (3,(51, 60, <boost/mpl/vector/aux_/numbered_c.hpp>))
#   include BOOST_PP_ITERATE()

}}

#endif // BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS

#endif // BOOST_MPL_VECTOR_VECTOR60_C_HPP_INCLUDED

（3）编译时生成方案（你的偏好）

要实现编译时自动生成而无需手动添加文件，需满足：

1. 确保定义BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS（测试代码中已定义）
2. 确保Boost预处理器工具链正常工作
3. 无需手动创建vector60.hpp，但需保证编译器能找到boost/mpl/vector/aux_/numbered.hpp（该文件默认已存在）

内容的提问来源于stack exchange，提问作者Darragh