https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118576
Bug ID: 118576
Summary: gcc does not realize implicitly deleted default
constructor in virtual inheritance with using-decl
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: accepts-invalid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rush102333 at gmail dot com
Target Milestone: ---
Consider the following code:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
struct A {
A(int);
};
struct B : virtual A { using A::A; };
struct C1 : virtual B { using B::B; };
struct D1 : virtual C1
{
using C1::C1;
};
D1 d1(0);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Clang rejects this by complaining that the default constructor of 'B' is
necessary here, which does not exist:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:14:4: error: constructor inherited by 'D1' from base class 'A' is
implicitly deleted
14 | D1 d1(0);
| ^
<source>:7:13: note: constructor inherited by 'D1' is implicitly deleted
because base class 'B' has a deleted corresponding constructor
7 | struct C1 : virtual B { using B::B; };
| ^
<source>:5:12: note: default constructor of 'B' is implicitly deleted because
base class 'A' has no default constructor
5 | struct B : virtual A { using A::A; };
| ^
1 error generated.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
EDG and ICC error for similar reasons:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"<source>", line 14: error: no default constructor exists for class "A"
D1 d1(0);
^
detected during implicit generation of "D1::A(int)" at line 14
1 error detected in the compilation of "<source>".
Compiler returned: 2
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
But gcc seems not: https://godbolt.org/z/5srhhqWeE
