https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109795
Bug ID: 109795
Summary: is_standard_layout incorrect for colliding member and
base class
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: myriachan at gmail dot com
Target Milestone: ---
The following compiles on GCC 13.1.0 when it should not:
struct X { };
struct Y {
X x;
};
struct Z : X {
Y y;
};
static_assert(!__is_standard_layout(Z));
By [class.prop]/3.7, rule 3.7.2 makes M(Z) = { Y } union M(Y). Applying 3.7.2
recursively results in M(Y) = { X } union M(X). By rule 3.7.1, M(X) = { }. So
M(Z) = { Y, X }. By rule 3.7, Z is not standard-layout, because Z's base class
X is an element of M(Z) = { Y, X }.
https://gcc.godbolt.org/z/oWhc8vs6z
