https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117317
Bug ID: 117317
Summary: An internal compiler error on call to virtual
constexpr function via comparison operator in CRTP
with multiple inheritance
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: kirshamir at gmail dot com
Target Milestone: ---
The following code results with internal compiler error:
class Base {
public:
constexpr bool operator==(const Base& b) const {
return getIdentity() == b.getIdentity();
}
private:
constexpr virtual int getIdentity() const = 0;
};
template<typename ActualType, typename Base1, typename... AdditionalBases>
class Comparable: public Base1, public AdditionalBases... {
public:
constexpr bool operator==(const Comparable&) const = default;
private:
constexpr int getIdentity() const override {
return 1;
}
};
class A: public Comparable<A, Base> {};
class B: public Comparable<B, Base> {};
class AB: public Comparable<AB, A, B> {};
int main() {
constexpr AB ab_1;
constexpr AB ab_2;
// internal compiler error :-(
static_assert(ab_1 == ab_2);
}
=====
Error:
<source>: In instantiation of 'constexpr int Comparable<ActualType, Base1,
AdditionalBases>::getIdentity() const [with ActualType = AB; Base1 = A;
AdditionalBases = {B}]':
<source>:4:27: required from here
4 | return getIdentity() == b.getIdentity();
| ~~~~~~~~~~~^~
<source>:31:24: in 'constexpr' expansion of 'ab_1.AB::Comparable<AB, A,
B>.Comparable<AB, A, B>::operator==(ab_2.AB::Comparable<AB, A, B>)'
<source>:13:20: in 'constexpr' expansion of '((const Comparable<AB, A,
B>*)this)->Comparable<AB, A, B>::A.A::Comparable<A, Base>.Comparable<A,
Base>::operator==(<anonymous>.Comparable<AB, A, B>::A.A::Comparable<A, Base>)'
<source>:13:20: in 'constexpr' expansion of '((const Comparable<A,
Base>*)this)->Comparable<A,
Base>::Base.Base::operator==(<anonymous>.Comparable<A, Base>::Base)'
<source>:17:5: internal compiler error: in use_thunk, at cp/method.cc:324
17 | }
| ^
0x287e175 diagnostic_context::diagnostic_impl(rich_location*,
diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag
(*) [1], diagnostic_t)
???:0
0x28945d5 internal_error(char const*, ...)
???:0
0xa90ace fancy_abort(char const*, int, char const*)
???:0
0xd1eb6b emit_associated_thunks(tree_node*)
???:0
0xd1ed0e expand_or_defer_fn(tree_node*)
???:0
0xcc60cd instantiate_decl(tree_node*, bool, bool)
???:0
0xb08a50 maybe_constant_value(tree_node*, tree_node*, mce_value)
???:0
0xd23df0 finish_static_assert(tree_node*, tree_node*, unsigned int, bool, bool)
???:0
0xc9e57a c_parse_file()
???:0
0xdf7f99 c_common_parse_file()
???:0
--------------
Notes:
1. Code compiles with clang: https://godbolt.org/z/j8oMxar8o
2. Removing the constexpr or the virtual from getIdentity() - code compiles:
https://godbolt.org/z/G5nMnWMd9 and https://godbolt.org/z/f3PWez1sb
3. Without CRTP code compiles: https://godbolt.org/z/56ah81n6h
