https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70347
Bug ID: 70347 Summary: [5.x Regression] default member initializer not picked up by union Product: gcc Version: 5.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: lichray at gmail dot com Target Milestone: --- #include <iostream> //struct A { union A { int a = 3; int b; }; //}; int main() { A c{}; std::cout << c.a << "\n"; } Prints 0 in 5.x, 3 in 4.9.2, same for anonymous union.