【问题标题】:Code works fine in debug mode but fails in normal run代码在调试模式下工作正常,但在正常运行中失败
【发布时间】:2017-03-01 11:37:13
【问题描述】:

当我使用指针时,这曾经经常发生在我身上。今天我有一个类似问题的代码。当我在调试模式下运行以下代码时,代码执行得非常好,并在 Code Blocks 13.12 中正常退出

当我尝试在正常模式下运行它时,它似乎遇到了分段错误,从而导致代码终止。在 print_board 函数的执行过程中,代码基本上会中断。但我不确定为什么会这样。

这是我的代码:

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

#define boardheight 8
#define boardwidth 8
struct Player_symbols{
    char symbol;
    char king_symbol;
};

struct Checker_piece{
    char king;
    int on_board;
    int num_moves;
    int player;
    struct Player_symbols* symbols;
};

int pieces_count[2] = {12,12};
struct Checker_piece* player_1_pieces;
struct Checker_piece* player_2_pieces;

void initialize_player_pieces(struct Checker_piece* player_pieces, struct Player_symbols* player_symbols, int player_num);
void initialize_board(struct Checker_piece* checker_board[boardheight][boardwidth],struct Checker_piece* player1,struct Checker_piece* player2);
void print_board(struct Checker_piece* checker_board[boardheight][boardwidth]);
int move_piece(struct Checker_piece* checker_board[boardheight][boardwidth], int x,int y,int player);
void continue_jumping(struct Checker_piece* checker_board[boardheight][boardwidth],int* y,int* x,int player);
int generate_destination(int x, int *dest_x, int *dest_y, int *dest_y_jump,int dest_y2,int dest_y2_jump,int move_flags,int player);

int main()
{
    struct Checker_piece*  checker_board[boardheight][boardwidth];
    //declare and initialize the Checker_piece structures by allocating memory dynamically using a dummy structure to determine its size
    player_1_pieces = malloc(12*sizeof (struct Checker_piece));
    player_2_pieces = malloc(12*sizeof (struct Checker_piece));
    struct Player_symbols *player_1_symbols,*player_2_symbols;

    player_1_symbols = malloc(sizeof (struct Player_symbols));
    player_2_symbols = malloc(sizeof (struct Player_symbols));

    //initialize the player symbols
    player_1_symbols->symbol = 'o';
    player_1_symbols->king_symbol = 'O';
    player_2_symbols->symbol = 'x';
    player_2_symbols->king_symbol = 'X';

    initialize_player_pieces(player_1_pieces,player_1_symbols,1);
    initialize_player_pieces(player_2_pieces,player_2_symbols,2);
    initialize_board(checker_board,player_1_pieces,player_2_pieces);
    print_board(checker_board);
    return 0;
}

void initialize_player_pieces(struct Checker_piece* player_pieces, struct Player_symbols* player_symbols, int player_num){
    int i;
    for (i = 0; i < 12; i++, player_pieces++ ) {
        player_pieces->king='N';
        player_pieces->num_moves=0;
        player_pieces->on_board=1;
        player_pieces->player=player_num;
        player_pieces->symbols= player_symbols;
    }
}

void initialize_board(struct Checker_piece* checker_board[boardheight][boardwidth],
                      struct Checker_piece* player1,struct Checker_piece* player2)
{
    int i, j;
    for(i = 0; i < 3; i++) {
        for(j = 0; j <= 7; j = j+2) {
            if(i == 0 || i % 2 == 0) {
                checker_board[i][j+1] = player1;
                checker_board[i][j] = malloc(sizeof (struct Checker_piece));
            } else {
                checker_board[i][j] = player1;
                checker_board[i][j+1] = malloc(sizeof (struct Checker_piece));
            }
            player1++;
        }
    }
    for(; i < 5; i++){
        for(j = 0; j < 8; j++){
            checker_board[i][j] = malloc(sizeof (struct Checker_piece));
        }
    }
    for(i = 5; i < 8; i++){
        for(j = 0; j <= 7; j = j+2){
            if(i == 0 || i % 2 == 0){
                checker_board[i][j+1] = player2;
                checker_board[i][j] = malloc(sizeof (struct Checker_piece));
            } else {
                checker_board[i][j] = player2;
                checker_board[i][j+1] = malloc(sizeof (struct Checker_piece));
            }
            player2++;
        }
    }
}
void print_board(struct Checker_piece* checker_board[boardheight][boardwidth]){
    int i = 0,j = 0;
    printf("\n   1   2   3   4   5   6   7   8\n");
    printf(" |---|---|---|---|---|---|---|---|\n");

    for(i = 0; i < 8; i++) {
        printf("%d|",(i + 1));
        for(j = 0; j < 8; j++) {
                if(checker_board[i][j]->king != '\r')
                    printf(" %c |",checker_board[i][j]->symbols->symbol);
                else
                    printf("   |");
        }
        printf("\n");
        printf(" |---|---|---|---|---|---|---|---|\n");
    }
}

【问题讨论】:

  • 如果j=6(会是这样),你认为checker_board[i][j+1] = ...这一行会发生什么?
  • 问题出在 print_board 函数的某个地方。其余代码工作正常。我通过评论 print_board 函数验证了这一事实。
  • 在这种情况下,您可能想了解术语未定义行为的含义。
  • 到目前为止,我的理解是我面临的 check_board 指针问题,我为其分配内存而不是为其分配一块。像 Checker_board[0][0] 指针
  • 所以你没有看到我指出的代码有问题??而且我认为这不是唯一的..

标签: c debugging pointers malloc codeblocks


【解决方案1】:

在查看源代码并使用调试器时,我已经确认了问题: 1- 在 print_board() 中,以下 test-if 检查未使用的值 '\'r':

if(checker_board[i][j]->king != '\r')

2- 在initialize_board()中,至少对于'king'参数,所有的malloc()都没有被初始化:

void initialize_board(struct Checker_piece* checker_board[boardheight][boardwidth],
                      struct Checker_piece* player1,struct Checker_piece* player2)
{
    int i, j;
    for(i = 0; i < 3; i++) {
        for(j = 0; j <= 7; j = j+2) {
            if(i == 0 || i % 2 == 0) {
                checker_board[i][j+1] = player1;
                checker_board[i][j] = malloc(sizeof (struct Checker_piece));
                // init at least the king to '\r'
                checker_board[i][j]->king = '\r';
            } else {
                checker_board[i][j] = player1;
                checker_board[i][j+1] = malloc(sizeof (struct Checker_piece));
                checker_board[i][j+1]->king = '\r';
            }
            player1++;
        }
    }
    for(; i < 5; i++){
        for(j = 0; j < 8; j++){
            checker_board[i][j] = malloc(sizeof (struct Checker_piece));
            checker_board[i][j]->king = '\r';
        }
    }
    for(i = 5; i < 8; i++){
        for(j = 0; j <= 7; j = j+2){
            if(i == 0 || i % 2 == 0){
                checker_board[i][j+1] = player2;
                checker_board[i][j] = malloc(sizeof (struct Checker_piece));
                checker_board[i][j]->king = '\r';
            } else {
                checker_board[i][j] = player2;
                checker_board[i][j+1] = malloc(sizeof (struct Checker_piece));
                checker_board[i][j+1]->king = '\r';
            }
            player2++;
        }
    }
}

【讨论】:

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