如何在typedef struct（C）中使用int数组

Question

can you please explain how to use int array in typedef struct?

In my header i have code:

typedef struct {
    int arr[20];
    int id;
} Test;

In some function (where i include my header file) i use:

Test tmp = malloc(sizeof(Test));
tmp.id = 1;
//and how to use array arr?
//for example I want add to array -1

Thank you for your reply.

Answer 1

If you want to do it dynamically

Test* tmp = malloc(sizeof(Test));
tmp->id = 1;        //or (*tmp).id = 1;
tmp->arr[0] = 5;    // or (*tmp).arr[0] = 5
                    // any index from 0 to 19, any value instead of 5 (that int can hold)

If you do not want to use dynamic memory

Test tmp;
tmp.id = 1;      //any value instead of 1 (that int can hold)
tmp.arr[0] = 1;  //any value instead of 1 (that int can hold)

EDIT

As suggested by alk in the comments,

Test* tmp = malloc(sizeof *tmp);

is better then

Test* tmp = malloc(sizeof(Test));

Since, to quote alk "The former would survive a change in the type definition of tmp without any further code changes"