https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96213
Bug ID: 96213
Summary: GCC doesn't complain about ill-formed non-dependent
template default argument
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: arthur.j.odwyer at gmail dot com
Target Milestone: ---
Possibly related (although these seem to complain about the opposite of what
I'm complaining about):
- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=12672
- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58071
// https://godbolt.org/z/EYzxx9
template<class> int g;
template<int = g<int>(0,1,2)>
void h() { }
int main() {
h<1>();
}
MSVC and Clang both reject template `h` as ill-formed, because `g<int>(0,1,2)`
is nonsense -- `g<int>` is an `int` and thus cannot be called like a function.
GCC accepts template `h` as well-formed, and in fact will treat this as a
SFINAE situation:
template<class> int g;
template<int = g<int>(42)> void h() {} // #1
template<class = void> void h() {} // #2
int main() {
h<>(); // unambiguously calls #2, because #1 has a deduction failure
}
My guess is that MSVC and Clang are closer to correct here.
