https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118428
Bug ID: 118428
Summary: Inherited virtual base class with a private destructor
is not rejected during instantiation of the
corresponding derived class
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: wangbopku15 at gmail dot com
Target Milestone: ---
Consider the following code:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
struct A{
virtual ~A();
};
struct B : private virtual A {};
struct C : private B{};
void foo(){
auto c=C{};
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Clang rejects it with the following diagnostic:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:6:8: error: inherited virtual base class 'A' has private destructor
6 | struct C : private B{};
| ^
<source>:9:12: note: in implicit default constructor for 'C' first required
here
9 | auto c=C{};
| ^
<source>:5:12: note: declared private here
5 | struct B : private virtual A {};
| ^~~~~~~~~~~~~~~~~
<source>:6:8: error: inherited virtual base class 'A' has private destructor
6 | struct C : private B{};
| ^
<source>:9:12: note: in implicit destructor for 'C' first required here
9 | auto c=C{};
| ^
<source>:5:12: note: declared private here
5 | struct B : private virtual A {};
| ^~~~~~~~~~~~~~~~~
2 errors generated.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
MSVC with:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>(6): warning C4594: class 'C' can never be instantiated - indirect
virtual base class 'A' is inaccessible
<source>(5): note: 'A' is a private base class of 'B'
<source>(6): warning C4624: 'C': destructor was implicitly defined as deleted
<source>(6): error C2282: 'C::~C' cannot override 'B::~B'
<source>(5): note: 'B::~B' is not deleted
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It seems that the instantiation of class 'C' should not be allowed as the
destructor of 'A' is private within 'B'.
But GCC accepts this:
https://godbolt.org/z/qdsz1oxq1
