Function pointers in a C struct

Question

I'm getting an error when I try to use a C function pointer inside of a struct (the function just pops the first element off of a linked list and returns the element):

main.c: In function ‘simulation’: main.c:279: error: incompatible types when assigning to type ‘struct PROCESS *’ from type ‘PROCESS’

My code is this:

typedef struct PROCESS {
    struct PS_TABLE *tbl_ref;
    int pid;
    int time_in_prev_state;
    int state_ts;
    int static_prio;
    int dynamic_prio;
    int cpu_rem;            
    struct PROCESS *next;
} PROCESS;

typedef void (*Add) (PROCESS *head, PROCESS *new_ps);
typedef PROCESS (*Get) (PROCESS *head);

typedef struct SCHEDULER {
    int quantum;
    sched_t sch_alg;
    Add add_process;
    Get get_next_process;
} SCHEDULER;

PROCESS *fcfs_get_next_proc(PROCESS **head) {     //POP
    PROCESS *tmp = head;
    head = tmp->next;
    tmp->next = NULL;
    return tmp;
}

SCHEDULER *scheduler_obj = malloc(sizeof(SCHEDULER));
scheduler_obj->get_next_process = fcfs_get_next_proc;

PROCESS *RUNNING_PROCESS = NULL;
RUNNING_PROCESS = scheduler->get_next_process(head_proc);

Any help would be really appreciated!

Answer 1

Your next struct field is a struct PROCESS *, and your function returns a PROCESS. Make them the same type and it will work.

typedef struct PROCESS *(*Get) (PROCESS *head);
typedef PROCESS *(*Get) (PROCESS *head);