Question

我有一个非常奇怪的情况，我已经升级到BOOST到版本1_56_0并且以前很好的代码不再用gcc 4.7.3编译。

代码是一个简单的模板，用于确定类型是否为boost::variant：

#ifndef BOOST_PP_IS_ITERATING

#ifndef BOOST_PP_TEST__H__
#define BOOST_PP_TEST__H__

#include <boost/preprocessor/repetition.hpp>
#include <boost/preprocessor/arithmetic/sub.hpp>
#include <boost/preprocessor/punctuation/comma_if.hpp>
#include <boost/preprocessor/iteration/iterate.hpp>

#include <boost/variant.hpp>
#include <boost/config.hpp>

/// ----------------------------------------------------------------------------|
/// namespace
/// ----------------------------------------------------------------------------|
namespace utils {

/// ----------------------------------------------------------------------------|
/// @brief primary trait template that returns false for non-variant types
/// @param T the type to check
template <class T>
struct is_variant_type
{ BOOST_STATIC_CONSTANT( bool, value = false ); };

/// ----------------------------------------------------------------------------|
// generate specializations of the is variant template
#define BOOST_PP_ITERATION_LIMITS (2, BOOST_VARIANT_LIMIT_TYPES )
#define BOOST_PP_FILENAME_1 "utils_lib_is_variant.h"   // this file
#include BOOST_PP_ITERATE()

} // namespace

#endif // BOOST_PP_TEST__H__

#else // BOOST_PP_IS_ITERATING

/// ----------------------------------------------------------------------------|
/// Use boost pre-processor to generated template specializations for
/// boost::variants with 2 to BOOST_VARIANT_LIMIT_TYPES parameters 
/// ----------------------------------------------------------------------------|
#define n BOOST_PP_ITERATION()
// specialization pattern
template <BOOST_PP_ENUM_PARAMS(n, class T)>
struct is_variant_type< boost::variant< BOOST_PP_ENUM_PARAMS(n,T) > >
{ BOOST_STATIC_CONSTANT( bool, value = true ); };

#undef n
#endif // BOOST_PP_IS_ITERATING

这段代码编译干净：

GCC 4.4.6-3使用BOOST版本1_56_0
GCC 4.4.6-3使用BOOST版本1_53_0
GCC 4.7.33使用BOOST版本1_53_0

但是当使用GCC 4.7.3和BOOST版本1_56_0编译时，我收到以下错误：

In file included from /opt/miniboost_1_56_0/boost/preprocessor/iteration/detail/iter/reverse1.hpp:1294:0,
             from     /opt/miniboost_1_56_0/boost/preprocessor/iteration/detail/iter/forward1.hpp:43,
             from utils_lib_is_variant.h:47,
             from is_variant.cpp:6:
./utils_lib_is_variant.h:62:67: error: wrong number of template arguments (0, should be 1 or more)
In file included from /opt/miniboost_1_56_0/boost/variant/variant.hpp:28:0,
             from /opt/miniboost_1_56_0/boost/variant.hpp:17,
             from utils_lib_is_variant.h:28,
             from is_variant.cpp:6:
/opt/miniboost_1_56_0/boost/variant/variant_fwd.hpp:291:53: error: provided for ‘template<class T0, class ... TN> class boost::variant’
In file included from /opt/miniboost_1_56_0/boost/preprocessor/iteration/detail/iter/reverse1.hpp:1294:0,
             from     /opt/miniboost_1_56_0/boost/preprocessor/iteration/detail/iter/forward1.hpp:43,
             from utils_lib_is_variant.h:47,
             from is_variant.cpp:6:
./utils_lib_is_variant.h:62:69: error: template argument 1 is invalid

我无法从GCC 4.7.3更改实时代码的编译器。有一个简单的方法吗？目前我的选择是：

恢复使用BOOST 1_53_0
放弃使用Boost预处理器并手动定义is_variant_type

使用BOOST 1.56和GCC 4.7.3提升预处理器错误（对于旧版本的boost，一切正常）

0 个答案: