Use of typedef struct

Question

typedef struct pjmedia_endpt pjmedia_endpt;

declaration of struct pjmedia_endpt endpt and pjmedia_endpt endpt are no ok("Variable has incomplete type struct pjmedia_endpt endpt").

i want to declare a variable of pjmedia_endpt, how to do.

Answer 1

Until unless you complete the incomplete type like this,

struct pjmedia_endpt
{
   member1;
   member2;
   ...
};

you can not use pjmedia_endpt .

Once you complete the structure, then you can use

pjmedia_endpt temp; // Declare a variable to it

Answer 2

Your typedef establishes a forward declaration. After this forward declaration you can define variables of type "pointer to pjmedia_endpt ", like this:

pjmedia_endpt *ptrVar;

However, forward declaration by itself is not enough to declare variables or struct fields until the actual definition is provided. You need to define the actual structure of pjmedia_endpt before you could start using your newly defied type pjmedia_endpt for variable declarations:

struct pjmedia_endpt {
    ...
};

Answer 3

You must use typedef to define a new type based on a predefined structure or a type. Otherwise you cannot declare a variable with that new type unless you define the pjmedia_endpt structure.

First define your structure:

struct pjmedia_endpt{
    // ...
};

Then you can assigne a type name to your structure:

typedef struct pjmedia_endpt pjmedia_endpt;

Then you can declare a variable with the new type:

pjmedia_endpt someVariable;

Answer 4

here is a function need pjmedia_endpt. pjmedia_transport_udp_create(pjmedia_endpt* endpt,...);

actually i what i need is a pointer,so instead

//declare a pointer.
pjmedia_endpt* endpt;
//do init endpt.then pass pointer to the function.
pjmedia_transport_udp_create(endpt,...);

Answer 5

typedef struct pjmedia_endpt{
    // ...
};

// Now Rename the structure

pjmedia_endpt newname;

// And now you can access the member of structure with newname.