https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98410
Bug ID: 98410
Summary: Default constructor generation fails on abstract class
with virtual base
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: thelordlucas at gmail dot com
Target Milestone: ---
Hi all,
The following code fails to compile on GCC > 7:
class Base {
int x;
public:
Base(int x): x{x} {}
virtual void f() = 0;
};
class Derived : public virtual Base {
public:
Derived() = default;
};
class Concrete: public Derived {
public:
Concrete(): Base{42} {}
void f() override {}
};
Link to code: https://godbolt.org/z/bn1EY6
It says that the Derived() constructor is deleted (error: use of deleted
function 'Derived::Derived()'). Using Derived() {}; it compiles file.
As the user eerorika points out in
https://stackoverflow.com/questions/65287323/strange-default-empty-constructor-on-a-virtual-inheritance-behaviour-on-gcc
the constructor Derived() should not have been deleted, since it is also
abstract and doesn't fall in any default constructor deletion rule.
Maybe related, it yielded "internal compiler error: in
maybe_explain_implicit_delete, at cp/method.c:2671" if I add the noexcept to
the deleted constructor:
class Base {
int x;
public:
Base(int x): x{x} {}
virtual void f() = 0;
};
class Derived : public virtual Base {
public:
Derived() noexcept = default;
};
class Concrete: public Derived {
public:
Concrete(): Base{42} {}
void f() override {}
};
Link to code: https://godbolt.org/z/5fx8Ph
I tested clang trunk, and it compiles both versions.
Thanks!
