如何在C中安全地使用枚举？

Question

consider the following example:

typedef enum {Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday} Day;
void DoSomething(Day day){
//some code
}

The problem is that the following code complies: DoSomething(74) . So how can I check in DoSomething that my parameter is really a Day? (relying on numbers won't work because if I change my enum like that Sunday=7 .... ,I want it to work too, and checking if(day==Sunday || day ==...) looks inefficient).

Answer 1

The short answer is you can't.

The long answer is you can try to put a "minimum" and a "maximum" member, and check that the value falls in the range between the two... or some other similar trick.

Answer 2

typedef enum {Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday, Last} Day;
void DoSomething(Day day){
   // if day < Last ...
}

Answer 3

You could put a switch statement in your DoSomething.

switch(day){
case Day.Monday:
     // something
    break
...
default: 
    // ignore or something

Answer 4

If you write DoSomething(74) statement in your code modern compiler generate warning saying DoSomething expect enum but integer is passed.

But if you are passing a value from user input where any value can be passed to DoSomething() then you will have to take care as other advised.