If you use switch(enum) you should not implement default: You will get a helpful warning when a value is not implemented. This is useful when new values will be added to the enum. You don't forget to handle the new value because of the warning. When a value doesn't need to be handle, add it at the end of the switch with a break.

No-Default.c

typedef enum MyEnum {
    MyEnum1,
	MyEnum2,
	MyEnum3,
} MyEnum;

static int function1(MyEnum e) {
	switch(e) { // warning: Enumeration value 'MyEnum3' not handled in switch
		case MyEnum1:
			return 1;
		case MyEnum2:
			return 2;
	}
	
	return 0;
}

static int function2(MyEnum e) {
	switch(e) {
		case MyEnum1:
			return 1;
		case MyEnum2:
			return 2;
			
		case MyEnum3: // implement unused enum values this way.
			break;
	}
	
	return 0;
}