c++ - 程序收到信号 EXC_BAD_ACCESS - Mac OS X

Question

当我将 std::vector 中的元素与 char 进行比较时，有时在运行程序时会随机出现此错误(大约每五次一次):

Program received signal EXC_BAD_ACCESS, Could not access memory.

Reason: 13 at address: 0x0000000000000000

0x0000000100017c49 in randomCaveGenerator (p=@0x7fff5fbff51c, q=@0x7fff5fbff518, seed=1234567) at src/main.cpp:198 198 if (lm.map[1][i][j] == '0')

v 被定义为填充了所有元素的 std::vector。我知道这个错误通常意味着它指向一个空指针但我知道不应该有一个。

我正在使用 Mac OS X 10.8，gdb 进行调试，Apple LLVM 4.2 版(基于 LLVM 3.2svn)进行编译。

编辑

我正在使用的代码:

typedef std::vector< std::vector<char> > MapGrid;

struct LevelMap
{
    std::string name;
    std::vector<MapGrid> map;
    sf::Vector2u size;
};


LevelMap randomCaveGenerator(int p=64, int q=64, unsigned long seed=1)
{

    if (p < 64)
         p = 64;
    if (q < 64)
         q = 64;

    int groundLevel = 12;

    srand(seed);

    sf::Vector2u size(p, q);
    std::vector<MapGrid> mapG(3);
    for (int i = 0; i < 3; i++)
    {
        mapG[i] = MapGrid(size.x, std::vector<char>(size.y));

        for (int y = 0; y < size.y; y++)
        {
            for (int x = 0; x < size.x; x++)
            {
                 mapG[i][x][y] = '0';
            }
        }
    }

    for (int y = 0; y < size.y; y++)
    {
        for (int x = 0; x < size.x; x++)
        {
            mapG[0][x][y] = 'v'; // Void Tile
        }
    }
    for (int y = 0; y < size.y; y++)
    {
        for (int x = 0; x < size.x; x++)
        {
            mapG[2][x][y] = '0'; // Air Tile
        }
    }

    for (int y = groundLevel; y < size.y; y++)
    {
        for (int x = 0; x < size.x; x++)
        {
            int e = 23;
            if (2+(rand()%e)< e/2)
                mapG[1][x][y] = 'd';
            else
                mapG[1][x][y] = '0';

        }
    }

    LevelMap lm;
    lm.name = "Random Map";
    lm.map = mapG;
    lm.size = size;

    for (int i = 0; i < 12; i++)
        doSimStep(lm);

    for (int i = 1; i < lm.size.x - 2; i++)
    {
        for (int j = 1; j < 12+groundLevel; j++)
        {
            if (lm.map[1][i][j] == '0') // PART WHERE THE ERROR IS
                continue;
            else
            {
                lm.map[1][i][j] = 'g';
                lm.map[2][i][j-1] = 'w';
                i++;
                j = 1;
            }
        }
    }

    for (int i = 1; i < lm.size.x - 2; i++)
    {
        for (int j = groundLevel; j < lm.size.y - 2; j++)
        {
            if (lm.map[1][i][j] == 'd')
            {
                if (rand()%120 == 0)
                    lm.map[2][i][j] = 'p';
            }
        }
    }

    for (int i = 0; i < lm.size.y; i++)
    {
        lm.map[1][0][i] = 'X';
        lm.map[1][lm.size.x-2][i] = 'X';
        lm.map[2][0][i] = '0';
        lm.map[2][lm.size.x-2][i] = '0';

    }

    for (int i = 0; i < lm.size.x; i++)
    {
        lm.map[1][i][0] = 'X';
        lm.map[1][i][lm.size.y-2] = 'X';
        lm.map[2][i][0] = '0';
        lm.map[2][i][lm.size.y-2] = '0';

    }

    return lm;
}

Answer 1

除了错误信息外没有源代码

 if (v[i] == '0')

我只能想象 i >= v.size()

您可能需要考虑使用迭代器来访问您的 vector ，这样您就不会离开末尾。