Здравствуйте, B0FEE664, Вы писали:

BFE>Это гарантируется каким стандартом? С или С++?

Про char[]:
If there are fewer initializers than there are array elements, each element not explicitly initialized shall be zero-initialized

UPD: более общее про Aggregates:
If there are fewer initializer-clauses in the list than there are members in the aggregate, then each member
not explicitly initialized shall be initialized from an empty initializer list