https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112820
Bug ID: 112820
Summary: vtable not emitted correctly from module when
compiling with -g
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: michael.kenzel at gmail dot com
Target Milestone: ---
When compiling a class with virtual member functions declared in a module
interface unit and defined in a module implementation unit with -g, the vtable
seems to not get emitted correctly, resulting in linker errors.
example:
// io.ixx
export module io;
export struct error
{
virtual const char* what() const noexcept;
};
// io-impl.cpp
module io;
const char* error::what() const noexcept
{
return "bla";
}
// main.cpp
import io;
int main()
{
error{};
}
compile with
g++ -std=c++23 -fmodules-ts -g -c -x c++ io.ixx
g++ -std=c++23 -fmodules-ts -g -c -x c++ io-impl.cpp
g++ -std=c++23 -fmodules-ts -g -c -x c++ main.cpp
g++ main.o io.o io-impl.o
produces
main.o: in function `error@io::error()':
main.cpp:3:(.text._ZNW2io5errorC2Ev[_ZNW2io5errorC5Ev]+0x8): undefined
reference to `vtable for error@io'
main.cpp:3:(.text._ZNW2io5errorC2Ev[_ZNW2io5errorC5Ev]+0xc): undefined
reference to `vtable for error@io'
Removing the -g from the first two commands resolves the problem, so this seems
to be tied to debugging information somehow. While the vtable will only be
emitted into io-impl.o, interestingly, it is apparently necessary to remove -g
from both the io-impo.o and the io.o commands for the vtable to be emitted.
