C accessing array correctly

Question

os-sim.h

typedef enum {
    PROCESS_NEW = 0,
    PROCESS_READY,
    PROCESS_RUNNING,
    PROCESS_WAITING,
    PROCESS_TERMINATED
} process_state_t;

typedef struct _pcb_t {
    const unsigned int pid;
    const char *name;
    const unsigned int static_priority;
    process_state_t state;               <<---Trying to access this
    op_t *pc;
    struct _pcb_t *next;
} pcb_t;

file1.c

static pcb_t **current;

extern void yield(unsigned int cpu_id)
{
    /* FIX ME */
    while (1)
    {
    pthread_mutex_lock(&current_mutex);
    current[cpu_id].state = PROCESS_WAITING;  ///<-------ERROR HERE
    pthread_mutex_unlock(&current_mutex);
    break;
    }
    schedule(cpu_id);
}

in main method():  
current = malloc(sizeof(pcb_t*) * 10);

I have error in this line current[cpu_id].state = PROCESS_WAITING;

error: request for member ‘state’ in something not a structure or union

What does this error mean?
Is this not the right way to access current array which holds pcb_t?
If so, how do i access the current array? and state field?

Bill Lynch · Accepted Answer · 2013-04-01 22:01:58Z

5

You're likely looking for:

current[cpu_id]->state = PROCESS_WAITING;

The type of current is pcb_t **. So the type of current[cpu_id] is pcb_t *.

answered Apr 1, 2013 at 22:01

Bill Lynch

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3 Comments

ealeon Over a year ago

so you use -> when it's ** and you use . when it's *?

user1944441 Over a year ago

@sharth Wait, if he allocated memory for only 10 pointers malloc(sizeof(pcb_t*) * 10) then how does that work? He can't store anything in state as space hasn't been allocated(?)

Bill Lynch Over a year ago

@Armin: That's a good point. I'd be happy to see you expand on that point in either a separate answer, as an edit to mine, or in these comments.

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