Consider the following code:
#include <iostream>
using namespace std;
class Outer {
struct Inner {
int num;
};
public:
static Inner GetInner() {
return Inner{-101};
}
};
// void func1(Outer::Inner inner) { // [1] Does not compile as expected
// cout << inner.num <<endl;
//}
template <typename Dummy>
void func2(Outer::Inner inner, Dummy = Dummy()) {
cout << inner.num << endl;
}
int main() {
// func1(Outer::GetInner()); // [2] does not compile as expected
func2<int>(Outer::GetInner()); // [3] How does this compile?
// Outer::Inner should not be accessible
// from outside Outer
return 0;
}
How is it that I am able to use an argument of type Outer::Inner
, which is a private type, in the non-member function func2
? ' func1
rightfully complains when I try and use it with the following error message:
prog.cpp: In function 'void func1(Outer::Inner)':
prog.cpp:5:9: error: 'struct Outer::Inner' is private
struct Inner {
^
prog.cpp:15:19: error: within this context
void func1(Outer::Inner inner) {
^
I am using g++4.8.2 on ubuntu, but I also see this on gcc-4.9.2 (on www.ideone.com)
You can try out the code here: Ideone
I get
Error 1 error C2248: 'Outer::Inner' : cannot access private struct declared in class 'Outer'
using Visual Studio 2013 update 4. Ergo, it is a problem in your compiler.
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