Struggling programming TicTacToe in C - c

Question

I'm new to C and programming and I tried to code a simple TicTacToe game. I new that I defintaly did many dumb things.
So I have a main .c file and two header files, which I will post here:
main.c:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "game.h"
#include "random.h"
#define NAMELENGTH 20
int main(void) {
char names[2][NAMELENGTH];
// field positions
char field[9];
int winner = -2;
getnames(names);
printf("\n\n");
initField(field);
// set field positions to 'empty'
char actualPlayer = (char)(get_random_number()*10.0) % 2;
while (1) {
drawField(field);
turn(actualPlayer, names, field);
winner = isWinner(actualPlayer, field);
drawField(field);
if (winner >= 0) {
printwinner(winner, names);
return 0;
}
else if (winner == -1) {
printDrawGame(names);
return 0;
}
actualPlayer = (actualPlayer + 1) % 2;
system("cls");
}
return 0;
}
game.h:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define NAMELENGTH 20
#pragma warning(disable:4996)
void drawField(char *field) {
printf("________________________\n");
printf("| | | |\n");
printf("| %c | %c | %c |\n", field[1], field[2], field[3]);
printf("|_______|_______|______|\n");
printf("| | | |\n");
printf("| %c | %c | %c |\n", field[4], field[5], field[6]);
printf("|_______|_______|______|\n");
printf("| | | |\n");
printf("| %c | %c | %c |\n", field[7], field[8], field[9]);
printf("|_______|_______|______|\n");
}
void getnames(char nameField[][NAMELENGTH]) {
printf("Name of the first player: ");
scanf("%s", &nameField[0]);
printf("Name of the second player: ");
scanf("%s", &nameField[1]);
}
void initField(char *field) {
for (int i = 1; i < 10; i++)
{
field[i] = i+48;
}
}
void turn(char actualPlayer, char names[][NAMELENGTH], char *field) {
char symbol = ' ';
int k;
int m;
if (actualPlayer == 1)
{
do {
printf("\nIts Player %s's turn.", names[0]);
char symbol = 'X';
printf("\nNumber of the field which you want to put your symbol in: ");
scanf("%i", &k);
if (field[k] == 'X' || field[k] == 'O')
{
printf("\nField is already occupied!");
k = 10;
}
} while (k < 1 || k > 9);
field[k] = 'X';
}
else {
do {
printf("\nIts Player %s's turn.", names[1]);
char symbol = 'O';
printf("\nNumber of the field which you want to put your symbol in: ");
scanf("%i", &m);
if (field[m] == 'X' || field[m] == 'O')
{
printf("\nField is already occupied!");
m = 10;
}
} while (m < 1 || m > 9);
field[m] = 'X';
}
}
int isWinner(char actualPlayer, char *field) {
int w = 2;
if (((field[1] = 'O') && (field[2] = '0') && (field[3] = '0')) || (field[4] = '0') && (field[5] = '0') && (field[6] = '0') || (field[7] = '0') && (field[8] = '0') && (field[9] = '0') || (field[1] = '0') && (field[5] = '0') && (field[9] = '0') || (field[3] = '0') && (field[5] = '0') && (field[7] = '0') || (field[1] = '0') && (field[4] = '0') && (field[7] = '0') || (field[2] = '0') && (field[5] = '0') && (field[8] = '0') || (field[3] = '0') && (field[6] = '0') && (field[9] = '0'))
{
int w = 1;
}
if (((field[1] = 'X') && (field[2] = 'X') && (field[3] = 'X')) || (field[4] = 'X') && (field[5] = 'X') && (field[6] = 'X') || (field[7] = 'X') && (field[8] = 'X') && (field[9] = 'X') || (field[1] = 'X') && (field[5] = 'X') && (field[9] = 'X') || (field[3] = 'X') && (field[5] = 'X') && (field[7] = 'X') || (field[1] = 'X') && (field[4] = 'X') && (field[7] = 'X') || (field[2] = 'X') && (field[5] = 'X') && (field[8] = 'X') || (field[3] = 'X') && (field[6] = 'X') && (field[9] = 'X'))
{
int w = 0;
}
else
{
int w = -1;
}
return w;
}
void printwinner(char winnerNumber, char names[][NAMELENGTH]) {
if (winnerNumber == 0)
{
printf("Player %s won!", names[0]);
system("exit");
}
else if (winnerNumber == 1)
{
printf("Player %s won!", names[1]);
system("exit");
}
}
void printDrawGame(char names[][NAMELENGTH]) {
printf("Draw!");
system("exit");
}
and random.h:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
static int _initialized;
void init() {
srand(time(NULL));
_initialized = 1;
}
double get_random_number() {
init();
if (!_initialized)
printf("Warning: init() should be called first!\n");
double random;
random = (double)rand() / ((double)(RAND_MAX)+1);
return random;
}
So the Program itself runs till I type in which field I want to put in the symbol. I get a weird error ("Stack around the variable 'field' was corrupted.") and also the random function doesnt work like I want. Would be happy and thankful for you help guys :)

Answer 1

You declared field to be an array of 9 elements. The indices will be 0 to 8. In game.h you have a function initField in which you do:
for (int i = 1; i < 10; i++)
{
field[i] = i+48;
}
This will produce indices 1 to 9, which steps out of bounds for the array.

Answer 2

You reinitialize the random number generator each time it is called. You pseudo random values will not be very random I'm afraid.
Fix it this way:
static int _initialized;
double get_random_number() {
if (!_initialized) {
srand(time(NULL));
_initialized = 1;
}
return = (double)rand() / ((double)(RAND_MAX)+1);
}
You should not write code in header files. Declarations belong in header files, code belongs in source files with the extension .c.