最小例子
class A
{
friend void swap(A& first,A& second) {}
void swap(A& other) {}
void call_swap(A& other)
{
swap(*this,other);
}
};
int main() { return 0; }
g 4.7说：
friend.cpp: In member function ‘void A::call_swap(A&)’: friend.cpp:7:20: error: no matching function for call to ‘A::swap(A&,A&)’ friend.cpp:7:20: note: candidate is: friend.cpp:4:7: note: void A::swap(A&) friend.cpp:4:7: note: candidate expects 1 argument,2 provided
流血线4：
// void swap(A& other) {}
解决方法
我相信这是因为编译器正在尝试在类中查找该函数.这应该是一个简单的更改,使其工作(它在Visual Studio 2012中工作)：
class A; // this and the next line are not needed in VS2012,but
void swap(A& first,A& second); // will make the code compile in g++ and clang++
class A
{
friend void swap(A& first,A& second) {}
void swap(A& other) {}
void call_swap(A& other)
{
::swap(*this,other); // note the scope operator
}
};
int main() { return 0; }
