Syntax of struct, union and enum in C

Question

Sometimes I just get so confused about the syntax in C. In struct, everything is separated by a semicolon and there is one extra semicolon after the last member, while in enum, everything is separated by a comma and there is no extra comma at the end. I always forget the last semicolon in struct since it doesn't seem to make sense to me. Is there any good reason for designing it that way? I hope someone can point out why it is good so that I can get used to it, right now it makes the syntax really hard to memorize.

Answer 1

Perhaps the simplest way to memorize this is that structs and unions are basically nested scopes. They contain declarations, just lie functions or your "root" document (in global scope).

So, you declare struct members:

struct {
    int member_a;
    int member_b;
} ;

Kind of like how you declare globals or function members:

/* START OF FILE */
int global_a;
int global_b;
/* END OF FILE */

Enums are lists -- kind of like array declarations, or multiple variables, etc...:

int arr[] = {1, 2, 3}; //* see note below
enum Foo { FOO, BAR, BAZ };
int foo, bar, baz;

// multiple "sub-statements" in one statement
// note that this is generally considered bad practice.
foo++, bar++, baz = bar;

---

Or you could simply remember it this way: Semicolons are statement terminators (they end statements), while commas are separators (they come between elements).

(*note: arrays are an exception in that they optionally allow for a trailing comma. As to why they allow for that in arrays while they don't allow it for enums is beyond me)

Answer 2

In C:

• A comma is a seperator. Between values. Example: enum.
• A semicolon is a terminator. of Statements and declerations.