C，体系结构x86_64的未定义符号

Question

I am writing a tic-tac-toe program for my CS class and I keep on getting this error when I go to compile.

Undefined symbols for architecture x86_64:
"_check_end_of_game", referenced from:
  _main in tictactoe-03b26b.o
"_generate_player2_move", referenced from:
  _main in tictactoe-03b26b.o
"_get_player1_move", referenced from:
  _main in tictactoe-03b26b.o
"_print_winner", referenced from:
  _main in tictactoe-03b26b.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see 
invocation)

Whenever I make all of my function declarations of the type 'void' the error message goes away, but not all of them are void so I can't do this. Here is what I have written so far.

#include <stdio.h>
#include <stdbool.h>
#define SIZE 3



void clear_table(char board[SIZE][SIZE]); void display_table(char 
board[SIZE][SIZE]); 
void get_player1_move(char board[SIZE][SIZE], int row, int col);
void generate_player2_move(char board[SIZE][SIZE], int row, int col); 
bool check_end_of_game(char board[SIZE][SIZE]); void print_winner(char 
board[SIZE][SIZE]);

int main (){
   char board[SIZE][SIZE];
   int row, col;


   clear_table(board);  //Clears the table
   display_table(board);  //Display the table

do {
      get_player1_move(board, row, col); //Have player 1 enter their move
      generate_player2_move(board, row, col); //Generate player 2 move
    } while(check_end_of_game(board) == false); //Do this while the game hasn't ended

    print_winner(board); //after game is over, print who won

   return 0;
 }

void display_table(char board[SIZE][SIZE]) {
   int i;
    printf("The current state of the game is: \n");
    for (i = 0; i <= SIZE; i++){
        for(i = 0; i <= SIZE; i++){
           printf("%c ", board[i][i]);
        }
     }
  }

void clear_table(char board[][SIZE]) {
    int i;
    for (i = 0; i <= SIZE; i++) {
       for (i = 0; i <= SIZE; i++) {
           int board[SIZE][SIZE] = {0};
        }
    }
}

I'm using VScode on Mac, coding in c, I'm compiling with 'gcc tictactoe.c -o tictactoe'

Answer 1

Make sure your definitions (implementations) have the same signature as the declarations. Then make sure you list all .c or .o files (depending on whether you compile the objects separately) in the final gcc command.

So if you compiled to objects, use:

gcc -o tictactoe tictactoe.c *.o

Or if your functions are just in other source files,

gcc -o tictactoe *.c