On Mon, Nov 27, 2023 at 8:24 PM Lew Robin via Gcc-bugs <gcc-bugs@gcc.gnu.org> wrote: > > This error happens when using macro and template. > GCC Version: gcc version 12.3.0 (Ubuntu 12.3.0-1ubuntu1~22.04) > OS: ubuntu 22.04 (x64) > Compile Command: > g++-12 ./testmacro.cc --std=c++20 > > In fact, this error exisits from g++11 to g++13. I also test it on clang and > msvc, but it cannot be reproduced.
GCC is correct here. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103593 which points to C++20 DR 2237 (and the bug about diagnostic that should be improved is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97202). I suspect clang and MSVC has not implemented that C++ defect report which is why it is accepted by those 2. Thanks, Andrew Pinski > > short reproduction: > #include <mutex> > > #define DECLARE_SINGLETON(classname_type) \ > public: \ > classname_type(); > > template <class MessageT> > class ReceiverManager > { > public: > ~ReceiverManager() { } > > private: > MessageT receiver_map_; > DECLARE_SINGLETON(ReceiverManager<MessageT>) > }; > > template <typename MessageT> > ReceiverManager<MessageT>::ReceiverManager(){} > > int main() > { > auto m = ReceiverManager<int>(); > return 0; > } > compile it and report error: > > ./testmacro.cc:5:24: error: expected unqualified-id before ‘)’ token > 5 | classname_type(); > | ^ > ./testmacro.cc:15:9: note: in expansion of macro ‘DECLARE_SINGLETON’ > 15 | DECLARE_SINGLETON(ReceiverManager<MessageT>) > | ^~~~~~~~~~~~~~~~~ > ./testmacro.cc:19:1: error: no declaration matches > ‘ReceiverManager<MessageT>::ReceiverManager()’ > 19 | ReceiverManager<MessageT>::ReceiverManager(){} > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > ./testmacro.cc:19:1: note: no functions named > ‘ReceiverManager<MessageT>::ReceiverManager()’ > ./testmacro.cc:8:7: note: ‘class ReceiverManager<MessageT>’ defined here > 8 | class ReceiverManager > | ^~~~~~~~~~~~~~~
