https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119844
--- Comment #3 from printfne at gmail dot com --- Thank you for the solution you proposed. It is indeed very useful. Besides, I want to know if the C++ standard has any regulations on the symbols exported in the module? For example, make them the same as those defined in the cpp file? nshead at gcc dot gnu.org <gcc-bugzi...@gcc.gnu.org> 于2025年4月29日周二 21:19写道： > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119844 > > Nathaniel Shead <nshead at gcc dot gnu.org> changed: > > What |Removed |Added > > ---------------------------------------------------------------------------- > Keywords| |diagnostic > CC| |nshead at gcc dot gnu.org > > --- Comment #2 from Nathaniel Shead <nshead at gcc dot gnu.org> --- > I haven't attempted to fully reproduce, but it appears to me you have > something > like the following: > > // user.cpp > export module User; > export struct User { > int value; > }; > > // main.cpp > struct User; > struct MainWindow { > User* u; > }; > import User; > int foo(MainWindow m) { > return m.u->value; > } > > $ g++-15 -fmodules -S user.cpp main.cpp > main.cpp: In function ‘int foo(MainWindow)’: > main.cpp:7:13: error: invalid use of incomplete type ‘struct User’ > 7 | return m.u->value; > | ^~ > main.cpp:1:8: note: forward declaration of ‘struct User’ > 1 | struct User; > | ^~~~ > > This error is expected (though the diagnostic could definitely be > improved!): > 'User' (in main.cpp) and 'User@User' (in user.cpp) are unrelated, distinct > types; the former belonging to the global module, and the latter attached > to > the module 'User'. You can see this by comparing e.g.: > > // main.cpp > struct User; > import User; > User u; > > $ g++-15 -fmodules -S user.cpp main.cpp > main.cpp:3:1: error: reference to ‘User’ is ambiguous > 3 | User u; > | ^~~~ > In module User, imported at main.cpp:2: > user.cpp:2:15: note: candidates are: ‘struct User@User’ > 2 | export struct User { > | ^~~~ > main.cpp:1:8: note: ‘struct User’ > 1 | struct User; > | ^~~~ > > To fix the issue, you could defined user.cpp as something like this: > > // user.cpp > export module User; > export extern "C++" struct User { > int value; > }; > > The 'extern "C++"' ensures that 'User' is declared attached to the global > module. > > I'll leave this PR open for now for the diagnostic issue, however, as I > imagine > this to be a common mistake, and we should be able to detect this and emit > some > kind of note pointing to the conflicting type. > > -- > You are receiving this mail because: > You reported the bug. > You are watching the reporter of the bug.
