https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69131
Bug ID: 69131
Summary: [4.9/5/6 Regression] default constructor of union
incorrectly deleted
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rs2740 at gmail dot com
Target Milestone: ---
From http://stackoverflow.com/q/34581372/2756719, repro:
struct X
{
~X() {}
};
union U
{
X x;
~U() {}
};
U u;
The default constructor of `X` is trivial. Nothing in [class.ctor]/4 applies,
so U's default constructor shouldn't be deleted. However, GCC 4.9 and later
rejects this code with:
prog.cc:12:3: error: use of deleted function 'U::U()'
U u;
^
prog.cc:6:7: note: 'U::U()' is implicitly deleted because the default
definition would be ill-formed:
union U
^
GCC 4.6-4.8 and all versions of Clang I tested accept this code.
