Allocate space for struct pointer in subfunction

Question

How can I allocate memory for a struct pointer and assign value to it\'s member in a subfunction?

The following code will compile but not execute:

#i         


        

Answer 1

In your example:

void allocate_and_initialize(struct _struct *s)
{
    s = calloc(sizeof(struct _struct), 1);
    s->str = calloc(sizeof(char), 12);
    strcpy(s->str, "hello world");
}

Assigning to s here doesn't change s in the caller. Why not return it instead?

struct _struct *allocate_and_initialize(void) {
    struct _struct *s;
    s = calloc(sizeof *s, 1);
    s->str = calloc(1, 12); /* sizeof(char) is always 1 */
    strcpy(s->str, "hello world");
    return s;
}

and use it thus:

struct _struct *s;
s = allocate_and_initialize();
/* use s... */
free(s); /* don't forget to free the memory when you're done */