Visual Studio 2015更新3改进了对C 11的支持,但我有一个奇怪的问题,我正在寻找解决方法.
当使用MSVC为模板类型参数(“完全定义的类型”)编译可变参数模板代码时,一切都很好,但是如果我想使用模板模板参数(“部分定义的类型”),则结果变得不正确.
#include <iostream>
using namespace std;
template <template<typename> class... TS>
struct PARTIAL {
static void test(std::ostream& out)
{
out << "PARTIAL-PROBLEM" << endl;
}
};
template <template<typename> class T>
struct PARTIAL<T>{
static void test(std::ostream& out)
{out << "PARTIAL-OK-END" << endl;}
};
template <template<typename> class T,template<typename> class... TS>
struct PARTIAL<T,TS...>{
static void test(std::ostream& out)
{
out << "PARTIAL-OK" << endl;
PARTIAL<TS...>::test(out);
}
};
template <class... TS>
struct FULL {
static void test(std::ostream& out)
{
out << "FULL-PROBLEM" << endl;
}
};
template <class T>
struct FULL<T>{
static void test(std::ostream& out)
{out << "FULL-OK-END" << endl;}
};
template <class T,class... TS>
struct FULL<T,TS...>{
static void test(std::ostream& out)
{
out << "FULL-OK" << endl;
FULL<TS...>::test(out);
}
};
template <typename T>
struct B{};
int main()
{
FULL<int,int,int>::test(cout);
PARTIAL<B,B,B>::test(cout);
return 0;
}
GCC5.3(MINGW)的输出：
FULL-OK FULL-OK FULL-OK-END PARTIAL-OK PARTIAL-OK PARTIAL-OK-END
MSVC的输出：
FULL-OK FULL-OK FULL-OK-END PARTIAL-OK PARTIAL-OK PARTIAL-OK PARTIAL-PROBLEM
解决方法
向递归案例添加另一个参数将确保不为终止案例选择它：
template <template<typename> class T,template<typename> class T2,template<typename> class... TS>
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
struct PARTIAL<T,T2,TS...>{
// ^^^^
static void test(std::ostream& out)
{
out << "PARTIAL-OK" << endl;
PARTIAL<T2,TS...>::test(out);
^^^^
}
};
