https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105465
Bug ID: 105465
Summary: С++14 behaviour of inherited constructors broken
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fchelnokov at gmail dot com
Target Milestone: ---
In the following program struct B inherits A(Foo) constructor, which is called
from main:
#include <iostream>
struct Foo {
Foo() {}
Foo(const Foo&) { std::cout << "Foo(const Foo&)\n"; }
};
struct A {
A(Foo) {}
};
struct B : A {
using A::A;
};
int main() {
Foo f;
B b(f);
}
According to C++14 standard
(https://timsong-cpp.github.io/cppwp/n4140/class.inhctor#8) the compiler shall
produce
B::B(Foo f) : A(f) { }
so the call `B(f)` leads to 2 copies of Foo and the program shall print:
Foo(const Foo&)
Foo(const Foo&)
And indeed GCC 6.4 prints so. But starting from GCC 7 only one copy is made.
Demo: https://gcc.godbolt.org/z/sTqKzdj5v
Related discussion: https://stackoverflow.com/a/56241478/7325599
Is it a regression?
