CODEWITHSUNDEEP
cfunctionpointersstructtypedef
TheAlPaca02
TheAlPaca02

Reputation: 523

Function pointing to a struct in c

I'm analyzing a bit of code and can't quite seem to grasp some of the workings behind it.

struct dplist {
  dplist_node_t * head;
};

struct dplist_node {
  dplist_node_t * prev, * next;
  element_t element;
};

dplist_t * dpl_create ()
{
  dplist_t * list;
  list = malloc(sizeof(struct dplist));
  DPLIST_ERR_HANDLER(list==NULL,DPLIST_MEMORY_ERROR);
  list->head = NULL;   
  return list;  
}

From the header file:

typedef int element_t;
typedef struct dplist dplist_t;
typedef struct dplist_node dplist_node_t;

In the main function:

dplist_t * list = NULL;

int main(void)
{
     list = dpl_create();
     return 0;
}

I'm not sure how to view the dpl_create() function which is declared as a pointer a dplist struct (i think?). Why does the function need to be declared as a pointer to a struct in order to correctly execute what is written inside the function?

Upvotes: 0

Views: 247

Answers (2)

Antokop
Antokop

Reputation: 122

The first element in the declaration of a function in C, before the function's name, is always the type of the variable it will return. In your case, the function is not declared as "a pointer to a struct", it just declares that it will return a pointer to a struct ("return list"). You can see another example in your code with the main function, which will return an INT ("return 0").

Upvotes: 2

areller
areller

Reputation: 5238

dpl_create() allocates a new dplist_t and returns it. In C you can't return objects that are dynamically allocated, you must return a reference(pointer) to them, hence 

dplist_t *

Upvotes: 0

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