Function CFSetSetValue 

pub unsafe extern "C" fn CFSetSetValue(
    theSet: CFMutableSetRef,
    value: *const c_void,
)

@function CFSetSetValue Replaces the value in the set if it is present, or adds the value to the set if it is absent. @param theSet The set to which the value is to be replaced. If this parameter is not a valid mutable CFSet, the behavior is undefined. @param value The value to set in the CFSet. The equal() callback provided when the set was created is used to compare. If the equal() callback was NULL, pointer equality (in C, ==) is used. If a value, or any of the values in the set, are not understood by the equal() callback, the behavior is undefined. The value is retained by the set using the retain callback provided when the set was created. If the value is not of the sort expected by the retain callback, the behavior is undefined. The count of the set is increased by one.