http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59312
Bug ID: 59312
Summary: Incorrect warning "defaulted move assignment for ...
calls a non-trivial move assignment operator for
virtual base ..."
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: alexander.o.khovansky at yandex dot com
Minimal test case:
#include <string>
struct A { std::string s; };
struct B : virtual A {};
int main(int argc, char* argv[]) {
B b1, b2;
b2 = b1;
}
This produces warning at line 3:
defaulted move assignment for ‘B’ calls a non-trivial move assignment operator
for virtual base ‘A’ [-Wvirtual-move-assign]
Tested on versions available on gcc.godbolt.org - 4.8.1, 4.9.0 20130909 - with
option -std=c++11.
The standard says the following.
12.8.20:
If the definition of a class X does not explicitly declare a move assignment
operator, one will be implicitly declared as defaulted if and only if
...
— the move assignment operator would not be implicitly defined as deleted.
12.8.23:
A defaulted ... move assignment operator for class X is defined as deleted if X
has:
...
— any direct or indirect virtual base class.
The B class does have virtual base, so it cannot have implicit move assignment
operator.
