模板代码上的编译器堆栈溢出

Question

在处理我自己的类型擦除迭代器时，我遇到了一个问题，即编译器 (MSVC10) 因此代码上的堆栈溢出而崩溃：

struct base {};  //In actual code, this is a template struct that holds data
template<class category, class valuetype>  
    struct any;  //In actual code, this is abstract base struct
template<class basetype, class category, class valuetype> 
    struct from; //In actual code, this is function definitions of any

template<class valuetype>
struct any<void,valuetype>
{ void a() {} };
template<class category, class valuetype>  
struct any
    : public any<void,valuetype> //commenting this line makes it compile
{ void b() {} };        

template<class basetype, class valuetype>
struct from<basetype,void,valuetype>
    : public base  //commenting out _either_ of these makes it compile
    , public any<void,valuetype>
{ void c() {} };

int main() {
    from<int, void, char> a;
    a.a();
    a.c();
    any<int, char> b;
    b.a();
    b.b();
    return 0;
}

很明显，我已经删除了所有可能存在错误的地方。 （原始代码是 780+ 行）删除任何剩余的模板参数会导致代码编译。

完整的错误信息是：

main.cpp(23): fatal error C1063: compiler limit : compiler stack overflow
    main.cpp(20) : see reference to class template instantiation 'from<basetype,void,valuetype>' being compiled

IDEOne compiles it fine。我听说 MSVC 实现了错误的两阶段查找，这似乎很相关，但没有解释为什么当我删除使 from 继承自 base 的行时它会编译。 谁能教我为什么 MSVC10 不能编译这个？我做了什么我应该避免的事情？

Answer 1

作为一种解决方法，请考虑在非专业化 any 和专业化 category = void 之间引入一个额外的类：

template <class valuetype>
class detail_void_any
    : public any<void, valuetype>
{
};


template<class category, class valuetype>
class any
    : public detail_void_any<valuetype>
{
};

下面的完整程序应该可以正常编译：

class base {};      // Data Holder (in reality it's templated, so required)
template<class category, class valuetype>  
        class any;  // Virtual Function Interface
template<class basetype, class category, class valuetype> 
        class from; // Virtual Function Implementation

template<class valuetype>
class any<void,valuetype>
{};


template <class valuetype>
class detail_void_any
    : public any<void, valuetype>
{
};

template<class category, class valuetype>
class any
    : public detail_void_any<valuetype>
{
};

template<class basetype, class valuetype>
class from<basetype,void,valuetype>
        : public base  //commenting out _either_ of these makes it compile
        , public any<void,valuetype>
{}; //this is line 23, where the compiler crashes

int main() {return 0;}

Answer 2

好吧，我放弃了，但我确实设法产生了警告：

template <typename T1, typename T2>
class Any; // forward

template <typename T2>
class Any<void, T2> // partial spec of forward
{};

template <typename T1, typename T2>
class Any: // template definition
    public Any<void, T2> // inherit from partial spec
{};

template <typename T1, typename T2>
class From :
    public Any<int, T2>, // inherit definition
    public Any<void, T2> // inherit definition or partial spec?
    // with spec first we get fatal error C1063: compiler limit : compiler stack overflow (CRASH!)
    // with definition first we get warning C4584: 'From<T1,T2>' : base-class 'Any<void,T2>' is already a base-class of 'Any<int,T2>'
{};

int main()
{
    return 0;
}

Answer 3

最简单的解决方法：替换：

template<class category, class valuetype>
class any : public any<void, valuetype>
{
};

与：

template<class valuetype, class category>
class any : public any<void, valuetype>
{
};