https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92968
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jakub at gcc dot gnu.org --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Because it is valid C (C99 and later), but invalid C++. While C++20 supports designated initializers, it only supports them with e.g. { .a = { 5, 0 } }. See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0329r4.pdf for details which even highlights the C vs. C++ differences with rationale.