https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109923
Bug ID: 109923
Summary: Template friend function defined in a template class
becomes a friend of all instantiations, not one
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: egor_suvorov at mail dot ru
Target Milestone: ---
The following code is accepted by all versions of GCC that I tried (including
"trunk" and 4.1.2 on Godbolt), but rejected by Clang and Visual Studio
(https://godbolt.org/z/z9f9qbPqb):
template<typename T>
struct MyTemplate {
private:
int x;
public:
MyTemplate() : x(0) {}
friend void non_templ_friend(MyTemplate val, MyTemplate<void> weird) {
// MyTemplate<T> is a friend of non_templ_friend(MyTemplate<T>,
MyTempl<void>)
val.x++; // always works
weird.x++; // should only work when T=void
}
};
int main() {
non_templ_friend(MyTemplate<int>(), MyTemplate<void>());
}
I expect that a new `non_templ_friend` is defined for each `T`. Each
`non_templ_friend` is a friend of the `MyTemplate<T>` it was created within.
Hence, it can only access internals of `MyTemplate<void>` if `T=void`. Hence,
`main()` should not compile: I call `non_templ_friend` created with `T=int`, it
should not be a friend of `MyTemplate<void>`.
