Dereferencing pointer to incomplete type

Applications Programming
1

// Hello all,
I am having this error "Dereferencing pointer to incomplete type " on these 2 lines:
xpoint = my_point->x;
ypoint = my_point->y;

I am having no clue y this is happening.

Any help would be greately appreciated!!!!

#include<stdio.h>
#include<string.h>
#include<pthread.h>

void *Client(void *);

struct coord{
 	long int x;
	long int y;
	};

struct coord my_coord;

int main()
{
long int i,j;
int rc;

printf("enter the coordinates");
scanf("%ld %ld", &i, &j);

my_coord.x = i;
my_coord.y = j;	

	pthread_t thread;
	rc = pthread_create(&thread,NULL, Client,(void *) &my_coord);
}

void *Client(void * threadarg)
{
	long int xpoint, ypoint;
	struct my_coord *my_point;
	
	my_point = (struct my_coord *) threadarg;
	xpoint = my_point->x;
	ypoint = my_point->y;

	printf("%ld", xpoint);
	printf("%ld", ypoint);
}
2

I was going to try to get you to code thru your problem, but there were several issues, not just the pointer problem. You HAVE to call pthread_wait in main() or the whole process will exit and the thread may or may not have ever executed Client(). So I just made a few changes and let it go with that.

I removed a bunch of intermediate variables, I left error checking up to you. Check return codes. Always.

#include<stdio.h>
#include<string.h>
#include<pthread.h>

void *Client(void *);

typedef
struct {
 	long int x;
	long int y;
	} coord_t;


int main()
{
  int rc=0;
  int *p=&rc;
  coord_t my_coord={0,0};
  pthread_t threadid;
  
  printf("enter the coordinates for i & j ");
  scanf("%ld %ld", &my_coord.x, &my_coord.y);
  rc = pthread_create(&threadid, NULL, Client, &my_coord);
  pthread_join(threadid, (void **)&p);
  return 0;
}

void *Client(void * threadarg)
{
	coord_t *p = (coord_t *) threadarg;
	
	printf("%ld ", p->x);
	printf("%ld\n", p->y);
	pthread_exit(0);
}
3

With your code was that you were typecasting wrongly.

I only changed typecasting and did some formatting of output. And yes, do follow the practice of returning a correct value, if your function is prototyped to return something ... The very same thing Jim had adviced you too.


#include<stdio.h>
#include<string.h>
#include<pthread.h>

void *Client(void *);

struct coord{
        long int x;
        long int y;
        };

struct coord my_coord;

int main()
{
long int i,j;
int rc;


printf("enter the coordinates : ");
scanf("%ld %ld", &i, &j);

my_coord.x = i;
my_coord.y = j;

        pthread_t thread;
        rc = pthread_create(&thread,NULL, Client,(void *) &my_coord);
        pthread_join(thread, NULL);
return 0;
}

void *Client(void * threadarg)
{
        long int xpoint, ypoint;
        struct coord *my_point;

        my_point = (struct coord  *) threadarg;
        xpoint = my_point->x;
        ypoint = my_point->y;

        printf("\n");
        printf("%ld\n", xpoint);
        printf("%ld\n", ypoint);

return NULL;
}

I'd definitely prefer the Jim's version of codes; however this is what you get as your own running code with the minimum amount of edition. Happy coding . :wink: