https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96592
Bug ID: 96592
Summary: Tuple element w/ member reference to incomplete
template type rejected
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: cuzdav at gmail dot com
Target Milestone: ---
Created attachment 49049
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49049&action=edit
source as shown in preview, g++10.2 preprocessed code, and the error messages
This code seems a regression introduced in g++ 10.1, is still in 10.2 and
remains in the trunk. It works on 9.x and as far back as g++ 6, plus all
versions of clang since 6, icc, msvc, etc.
There are many independent changes that can make it work, including:
* making SomeQuery constructor a template constructor (on SessionU)
* changing the reference to a pointer
* explicitly declaring Session as an incomplete type and not using
templates
#include <tuple>
template <typename SessionT>
struct SomeQuery {
SessionT& session_;
SomeQuery(SessionT& session) : session_(session) {}
};
template <typename SessionT>
struct Handler {
std::tuple<SomeQuery<SessionT>> queries_;
Handler(SessionT& session) : queries_(session) {}
};
struct Session {
Handler<Session> handler_;
Session() : handler_{*this} {}
};
int main() {
Session session;
}
It looks like the tuple class is doing some concept checking that isn't quite
working, but I haven't dug deeply enough to determine if it's a library or
underlying compiler issue.
Live example on Compiler Explorer
https://godbolt.org/z/7naPMx
