https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120183
Bug ID: 120183
Summary: Incomplete type error in module import
Product: gcc
Version: 15.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rafel.perello at upc dot edu
Target Milestone: ---
Created attachment 61375
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61375&action=edit
Code and makefile
// module.cpp
export module mod;
export import <array>;
export template<int a, std::array<int, (a == -1) ? 0 : a> b>
class A {};
template<int a, std::array<int, (a == -1) ? 0 : a> b> requires(a == -1)
class A<a, b> {};
template<int a, std::array<int, (a == -1) ? 0 : a> b> requires(a != -1)
class A<a, b> : public A<-1, std::array<int, 0>{}> {};
// main.cpp
import mod;
#ifdef DEFINE_B
template<int a, std::array<int, (a == -1) ? 0 : a> b>
class B {};
template<int a, std::array<int, (a == -1) ? 0 : a> b> requires(a == -1)
class B<a, b> {};
template<int a, std::array<int, (a == -1) ? 0 : a> b> requires(a != -1)
class B<a, b> : public B<-1, std::array<int, 0>{}> {};
#endif
int main()
{
A<0, std::array<int, 0>{}> a{};
#ifdef DEFINE_B
B<0, std::array<int, 0>{}> b{};
#endif
}
The above code does not compile on g++ 15.1.0 running the following commands:
g++ -std=c++26 -fmodules-ts -xc++-system-header array
g++ -std=c++26 -fmodules-ts module.cpp -c
g++ -std=c++26 -fmodules-ts main.cpp -o main
It complains about A having incomplete type. However, it compiles if the last
command is substituted by
g++ -std=c++26 -fmodules-ts main.cpp -o main -DDEFINE_B
That is, the class B is defined in the same exact way than A but in the main
file. In this case, both uses of the classes are valid.
