typedef in C difference?

Question

What is the difference between the following in C language:

typedef enum month_t
{
jan,
feb,
march
}month;

AND

typedef enum
{
monday,
tuesday,
wednesday
}day;

Before posting this question I read this : What is a typedef enum in Objective-C?

But did not understand quite well...

In the first case, you could have left off the `month_t` and then the two would be the same way of doing it. The `month_t` is just another type tag in C one can use, so you could declare a month as `enum month_t my_month;` or just `month my_month;`. For day, you can only do `day my_day;` the way it's currently defined. — lurker, May 24 '13 at 13:18
@KerrekSB: That is not actually a difference in the C language; there is an isomorphism between them. It is only a difference outside the C language, to its users. — Eric Postpischil, May 24 '13 at 13:21

score 11 · Accepted Answer · answered May 24 '13 at 13:16

11

The first also introduces an enum tag, which means the enumeration can be used like this:

enum month_t first = jan;
/* or */
month second = feb;

the second doesn't, so the enumeration is only available with the typedef:ed name day.

Also, of course, the enumerations themselves are different, but that's kind of obvious.

answered May 24 '13 at 13:16

unwind

2

Yes (upvoted). Putting it another way, the first declares an enum called 'month_t' and typedefs an alias called 'month'. The second declares an anonymous enum and types an alias called 'day'. – davmac May 24 '13 at 13:18

1 Answers1