https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87652
Bug ID: 87652
Summary: inner class template of outer class template can't
access friend's protected data member
Product: gcc
Version: 8.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: haining.cpp at gmail dot com
Target Milestone: ---
#### Example program ####
template <typename>
struct Outer {
template <typename>
class Inner {
template <typename>
friend class Inner; // All Inners should be friends
public:
template <typename T>
void use_other_x(const Inner<T>& other) const {
(void)other.x; // should be fine, we're all friends
}
private: // no error if private instead
int x;
};
};
int main() {
Outer<int>::Inner<void> i1;
Outer<int>::Inner<char> i2;
i1.use_other_x(i2);
}
#### Error message ####
prog.cc: In instantiation of 'void Outer< <template-parameter-1-1> >::Inner<
<template-parameter-2-1> >::use_other_x(const Outer< <template-parameter-1-1>
>::Inner<T>&) const [with T = char; <template-parameter-2-1> = void;
<template-parameter-1-1> = int]':
prog.cc:21:20: required from here
prog.cc:11:20: error: 'int Outer<int>::Inner<char>::x' is protected within this
context
(void)other.x;
~~~~~~^
prog.cc:14:10: note: declared protected here
int x;
#### Notes ####
No problems observed when using private: instead of protected:
