c/language/attributes/fallthrough

Indicates that the fall through from the previous case label is intentional and should not be diagnosed by a compiler that warns on fallthrough.

Explanation
May only be used in an attribute declaration to create a fallthrough declaration.

A fallthrough declaration may only be used in a statement, where the next block item (statement, declaration, or label) to be encounted is a statement with a  or  label for that switch statement.

Indicates that the fall through from the previous case label is intentional and should not be diagnosed by a compiler that warns on fallthrough.