Use this attribute to ensure that values of a struct or union type are not discarded.
Use this attribute to make an Objective-C interface method optional.
Use this attribute to specify that a global symbol should be emitted with weak linkage. This is primarily useful in defining library functions that can be overridden by user code, though it can also be used with shared and static variables too.
This module contains UDA's (User Defined Attributes) either used in the runtime or special UDA's recognized by compiler.