https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102995
Bug ID: 102995
Summary: Template friend class declaration of same class with
different template parameters fails to allow private
methods access
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jdapena at igalia dot com
Target Milestone: ---
Created attachment 51698
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51698&action=edit
Test case
Declaring a template friend class to the same class fails to resolve the access
to private members in its methods.
The provided example fails with this error:
$ g++ main.cc
main.cc: In instantiation of 'bool operator==(const First<A, B>&, const
First<C, B>&) [with C = void*; A = int; B = bool]':
main.cc:23:15: required from here
main.cc:13:61: error: 'int First<A, B>::GetId() const [with A = void*; B =
bool]' is private within this context
13 | return lhs.GetId() == rhs.GetId();
| ~~~~~~~~~^~
main.cc:6:9: note: declared private here
6 | int GetId() const {
| ^~~~~
The same case works in Clang (verified with Clang 9.0.1).
This issue is exposed in Chromium, compiling base/raw_ptr.h unit tests on GCC.
I created a simplified version of the problem. See:
https://chromium.googlesource.com/chromium/src/base/+/821f1e481ce7c51d31486f26a74d343ffe4cf70e/memory/raw_ptr.h#496
(declaration of the method that should have friend access to rhs private
methods).
https://chromium.googlesource.com/chromium/src/base/+/821f1e481ce7c51d31486f26a74d343ffe4cf70e/memory/raw_ptr.h#584
(the friend class declaration).
https://chromium.googlesource.com/chromium/src/base/+/821f1e481ce7c51d31486f26a74d343ffe4cf70e/memory/raw_ptr_unittest.cc#328
(failing test compilation).
