概念檢查編譯錯誤上的gcc

Question

我試圖應用於http://www.drdobbs.com/tools/227500449

隨着下面的代碼示例中描述的技術，我期望的輸出：

而且這確實是發生了什麼如果我用clang編譯的話。但是用gcc，這個代碼給出了以下錯誤：

junk.cpp: In instantiation of ‘const bool has_foo_member_variable<B>::value’: 
junk.cpp:45:5: instantiated from ‘void print() [with T = B]’ 
junk.cpp:82:14: instantiated from here 
junk.cpp:30:75: error: ‘B::foo’ is not a valid template argument for type ‘int B::*’ 
junk.cpp:30:75: error: it must be a pointer-to-member of the form `&X::Y' 
junk.cpp: In instantiation of ‘const bool has_foo_member_variable<D>::value’: 
junk.cpp:45:5: instantiated from ‘void print() [with T = D]’ 
junk.cpp:84:14: instantiated from here 
junk.cpp:30:75: error: ‘& D::foo’ is not a valid template argument for type ‘int D::*’ 
junk.cpp:30:75: error: it must be a pointer-to-member of the form `&X::Y' 

我用gcc 4.5.1 ......我看起來像的gcc沒有按照正確的SFINAE規則，但我不是100％肯定。鏗鏘聲是否正確，這是一個gcc錯誤？

#include <iostream> 

struct small_type { char dummy; }; 
struct large_type { char dummy[2]; }; 

template<class T> 
struct has_foo_member_function 
{ 
    template<int (T::*)()> struct tester; 
    template<class U> static small_type has_foo(tester<&U::foo> *); 
    template<class U> static large_type has_foo(...); 
    static const bool value = (sizeof(has_foo<T>(0)) == sizeof(small_type)); 
}; 

template<class T> 
struct has_foo_static_member_function 
{ 
    template<int (*)()> struct tester; 
    template<class U> static small_type has_foo(tester<&U::foo> *); 
    template<class U> static large_type has_foo(...); 
    static const bool value = (sizeof(has_foo<T>(0)) == sizeof(small_type)); 
}; 

template<class T> 
struct has_foo_member_variable 
{ 
    template<int T::*> struct tester; 
    template<class U> static small_type has_foo(tester<&U::foo> *); 
    template<class U> static large_type has_foo(...); 
    static const bool value = (sizeof(has_foo<T>(0)) == sizeof(small_type)); 
}; 

template<class T> 
struct has_foo_static_member_variable 
{ 
    template<int *> struct tester; 
    template<class U> static small_type has_foo(tester<&U::foo> *); 
    template<class U> static large_type has_foo(...); 
    static const bool value = (sizeof(has_foo<T>(0)) == sizeof(small_type)); 
}; 

template<class T> 
void print() 
{ 
    std::cout << has_foo_member_function<T>::value << " " 
     << has_foo_static_member_function<T>::value << " " 
     << has_foo_member_variable<T>::value << " " 
     << has_foo_static_member_variable<T>::value << "\n"; 
} 

struct A 
{ 
    int foo() 
    { 
     return 0; 
    } 
}; 

struct B 
{ 
    static int foo() 
    { 
     return 0; 
    } 
}; 

struct C 
{ 
    int foo; 
}; 

struct D 
{ 
    static int foo; 
}; 

int main() 
{ 
    print<A>(); 
    print<B>(); 
    print<C>(); 
    print<D>(); 
} 

Answer 1

你的代碼是正確的。

鐺是正確的，這是一個海灣合作委員會的錯誤？

是最有可能的。 Comeau確認您的代碼是正確的。