c - segmentation fault because of character changement -

i'm writing board game detailed information. segmentation fault changing problem_ch ' '(space) '.'. when play moves , ' ', don't when play moves , '.'i get. , don't understand happening.

solved: because of negative index, segmentation fault. handling, solved.

following moves:

3d 2d 5f 2e 1e 4b 4c 4a 3b @ 4b segmentation fault 

code:

void make_move(char board[][size], size_t row, size_t col, char player) {     int rowdelta = 0;                     // row increment     int coldelta = 0;                     // column increment     size_t x = 0;                         // row index searching     size_t y = 0;                         // column index searching      // identify opponent     char opponent = (player == player_ch) ? computer_ch : player_ch;      board[row][col] = player;             // place player counter      // check squares around square opponents counter     for(rowdelta = -1 ; rowdelta <= 1 ; ++rowdelta)         for(coldelta = -1; coldelta <= 1; ++coldelta)         {             // don’t check off board, or current square             if((row == 0 && rowdelta == -1) || row + rowdelta >= size ||                (col == 0 && coldelta == -1) || col + coldelta >= size ||                (rowdelta == 0 && coldelta == 0))                 continue;              // check square             if(board[row + rowdelta][col + coldelta] == opponent)             { // found opponent search in same direction player counter                 x = row + rowdelta;           // move opponent                 y = col + coldelta;           // square                  for(;;)                 {                     x += rowdelta;              // move                     y += coldelta;              // next square                       if(board[x][y] == problem_ch)      // if square blank...                         break;                    // ...give                      // if find player counter, go backward here                     // changing opponents counters player                     if(board[x][y] == player)                     {                         while(board[x -= rowdelta][y -= coldelta] == opponent) // opponent?                             board[x][y] = player;                                // yes, change                          break;                      // done                     }                 }             }         } }