error: redeclaration of ‘y2’ with no linkage

Question

I am tring to create a program that recieves integer values and converts them into 2's complement integers using atoi, and determines what type of turn was made. Here is my code:

#include <stdio.h>
#include <stdlib.h>

int turn(int turn, int a1, int b1, int a2, int b2, int a3, int b3){
;
  turn = ((a1 * b1 + b1 * a3 + a2 * a3) - (b2 * a3 + a1 * b3 + a2 * b1));
  printf("\n value = %d \n", turn);

  return(turn);
}

int main( int argc, char *argv[] ) {

  int x1, y2, x2, y2, x3, y3, turn;

  x1 = atoi(argv[1]);
  y1 = atoi(argv[2]);
  x2 = atoi(argv[3]);
  y2 = atoi(argv[4]);
  x3 = atoi(argv[5]);
  y3 = atoi(argv[6]);

  turn = turn(x1, y1, x2, y2, x3, y3);

  if(turn == 0) printf("\n Straight \n");
  if(turn < 0) printf("\n Right Turn \n");
  if(turn > 0) printf("\n Left Turn \n");

  return 0 ;

}

And my errors:

make -k p3
cc     p3.c   -o p3
p3.c: In function ‘main’:
p3.c:29:19: error: redeclaration of ‘y2’ with no linkage
p3.c:29:11: note: previous declaration of ‘y2’ was here
p3.c:32:3: error: ‘y1’ undeclared (first use in this function)
p3.c:32:3: note: each undeclared identifier is reported only once for each function it appears in
p3.c:38:14: error: called object ‘turn’ is not a function
make: *** [p3] Error 1

Compilation exited abnormally with code 2 at Sun Sep 22 20:07:02"

I am wondering the cause of this error.

Thanks,

Answer 1

The errors that you are getting are exactly what the message is telling you.

• You are declaring your variable y2 twice
• You did not declare y1 anywhere
• You can't have two members with the same name like this. You have a turn variable which has the same name as your turn function.