https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104264
Bug ID: 104264
Summary: __is_trivially_copyable fails to report
non-recursively trivially copyable classes
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: accepts-invalid, rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: de34 at live dot cn
Target Milestone: ---
The current definition of trivially copyable class ([class.prop]
/2) is not recursive. I.e. a trivially copyable class may have a base class or
data member of a non-trivially copyable class type.
The following example is accepted by clang, msvc, and icc, but rejected by gcc
(all of which use __is_trivially_copyable). Perhaps gcc considers Supressor as
non-trivially copyable because it has a non-trivially copyable data member.
struct Weird {
Weird() = default;
Weird(const Weird&) = default;
Weird &operator=(const Weird&) = default;
// non-trivial
constexpr Weird(Weird&&) noexcept {}
constexpr Weird &operator=(Weird&&) noexcept { return *this; }
};
struct Supressor {
Weird w;
Supressor() = default;
Supressor(const Supressor&) = default;
Supressor &operator=(const Supressor&) = default;
// move functions are supressed
// non-trivial move functions are not called
};
int main()
{
static_assert(!__is_trivially_copyable(Weird), "");
static_assert(__is_trivially_copyable(Supressor), "");
}
Compiler Explorer link: https://gcc.godbolt.org/z/4o1vPdz86
The issue might be related to CWG 2463 (https://wg21.link/cwg2463). CWG DR 1734
seems unrelated,
