Different syntax of structure in C

Question

What are the different syntax of c structure? How do decode this :

struct p {
    char a[1];
    int b;
    int *a;
    int value;
};
struct p q[] = {
    {"a",      0, &b, C},
    {"J",      0, &k, l}
};

I found a another discussion here but didn't encounter this type.

You are posting a struct initialization yet link to a post discussing various forms of struct declaration sytax. Those are different things, so it is unclear what you are asking here. — Lundin, Feb 19 '15 at 10:22

Vagish · Accepted Answer · 2015-02-19T10:23:16.680

5

q is the array of structure of type p.

p has following elements:

char pointer
any type (int,char,short etc. even a pointer is possible)
pointer to any type
should be a constant

The syntax is actually initializing q[0] and q[1]

edited Feb 19 '15 at 10:23

answered Feb 19 '15 at 10:17

Vagish

2,520
19
32

Is it equivalent to: struct p { }q[]; ? – Shivendra Mishra Feb 19 '15 at 10:19
@SHIVENDRAMISHRA It is almost same,only difference is that `struct p { }q[];` does not have member initialization. – Vagish Feb 19 '15 at 10:36
@Vagish Why `char*` and not simply `char` for the first element? There's nothing that recalls a pointer in the first element. – Alberto Coletta Feb 19 '15 at 11:37
@boh `"a"` is a `string` NOT a `char` – Vagish Feb 19 '15 at 12:20

tom · Answer 2 · 2015-02-19T10:28:04.247

1

That is declaring an array called q of type struct p, it is not actually defining a struct at all. The {"a", 0, etc...}'s inside the initialization list are creating the structs that populate the first and second element of the array by defining values for the structs fields, and in doing so, creating instances of the struct on the stack.

struct p appears to contain a char*,

an integer,

some other pointer

and something else(probably an integer).

edited Feb 19 '15 at 10:28

answered Feb 19 '15 at 10:21

tom

354
4
15

Is it called C99 style ? – Shivendra Mishra Feb 19 '15 at 10:21
I'm not entirely sure, I would assume it was new in C99. I am just going from what I can infer from the code you posted. – tom Feb 19 '15 at 10:22

Different syntax of structure in C

2 Answers2