C++ std::vector 迭代器错误

Question

首先，我很抱歉我的英语不好，希望你们能理解我:) 我正在编写 WinAPI 游戏，我的类表现得很奇怪:所有操作都使用 vector使我的程序崩溃所以 Windows 说我的 .exe 停止工作。但是当我调试这些行时我得到异常。

这是我的类标题的样子:

#ifndef FIGURE_H_INCLUDED
#define FIGURE_H_INCLUDED

#include <vector>
#include <Windows.h>
#include "Other.h"

using namespace std;

enum Figure_Type { I, J, L, O, S, T, Z };

class Figure
{
public:
    /* CONSTRUCTORS */
    Figure();
    Figure(Figure_Type);

    /* MOVEMENT */
    bool                Move(vector<Cell>&, Direction&);
    void                Drop(vector<Cell>&);
    bool                Rotate(vector<Cell>&);

    /* OTHER */ 
    void                Draw(HDC&);

private:

    /* METHODS */   
    void                Generate();
    void                GenerateMasks();
    void                GenerateFigure();
    Figure              GetFigureCopy() const;  

    /* DATA */
    Shift               shift;
    char                mask[4][4];
    vector<Cell>        vCells;
    Figure_Type         type;
    int                 rotation;
};

#endif

我的构造函数正在使用 Generate() 方法，代码是:

void Figure::GenerateFigure()
{
    vCells.clear();
    int defPosX = 4,
            defPosY = 20;
    Cell    cell;

    for(int y = 0; y < 4; y++)
    {
        for(int x = 0; x < 4; x++)
        {
            if(mask[y][x] == '0')
            {
                cell.x = defPosX + x + shift.dx;
                cell.y = defPosY - y + shift.dy;
                vCells.push_back(cell);
            }
        }
    }
}

而且我在 vCells.clear() 方法和(如果我评论第一行)vCells.push_back(cell) 行上遇到异常。实际上，使用 vector/vector 迭代器的每个操作都会使我的程序崩溃，甚至递增迭代器，这些只是第一个，所以我的代码在它们之后不再运行。异常文本:

“Tetris_completely_new.exe 中 0x5A4ACCD2 (msvcp110d.dll) 处的未处理异常:0xC000041D:在用户回调期间遇到未处理的异常。”

并且这些异常是在 217 的“xutility”行中抛出的。我评论它:

....
// MEMBER FUNCTIONS FOR _Container_base12
inline void _Container_base12::_Orphan_all()
    {   // orphan all iterators
 #if _ITERATOR_DEBUG_LEVEL == 2
    if (_Myproxy != 0)
        {   // proxy allocated, drain it
        _Lockit _Lock(_LOCK_DEBUG);

        for (_Iterator_base12 **_Pnext = &_Myproxy->_Myfirstiter;
            *_Pnext != 0; *_Pnext = (*_Pnext)->_Mynextiter)
            **(*_Pnext)->_Myproxy = 0;**    // <------------ THIS LINE
        _Myproxy->_Myfirstiter = 0;
        }
 #endif /* _ITERATOR_DEBUG_LEVEL == 2 */
    }
....

这是我的单元格结构的样子:

struct Cell
{
    Cell() : x(1), y(1) { }
    Cell(int _x, int _y): x(_x), y(_y) { }

    void Draw(HDC&) const;

    bool operator ==(const Cell& a) const { return (x == a.x && y == a.y); } 
    bool operator !=(const Cell& a) const { return !(*this == a); } 

    int x;
    int y;
};

和图形构造函数:

Figure::Figure()
{
    srand(time(NULL));

    vCells.clear();
    type = Figure_Type(rand() % 7);
    rotation = 0;
    shift.dx = 0;
    shift.dy = 0;

    Generate();
}

Answer 1

您可能会调用未定义的行为。

如果没有更多信息，我会说您正在通过陈旧的对象引用/指针调用实例方法(在回调注册时获取的引用不再有效？)。

此外，正如目前问题中所写，您正在根据 mask 中的未初始化字节生成一个图形，因此您可能也想初始化它们。

这是一个稍微现代化/清理过的版本。注意

• 初始化列表的使用
• 统一初始化
• 重新排序成员初始化
• 不在 header 中使用using namespace
• 将 srand 移动到 main 而不是构造函数

查看Live on Coliru

#ifndef FIGURE_H_INCLUDED
#define FIGURE_H_INCLUDED

#include <vector>

#ifdef _WIN32
#   include <Windows.h>
#   include "Other.h"
#else
#   include <cstdint>
#   include <cstdlib>
#   include <ctime>

using HDC = uint32_t;
#endif

struct Cell
{
    Cell(int _x=1, int _y=1): x(_x), y(_y) { }

    void Draw(HDC&) const;

    bool operator ==(const Cell& a) const { return (x == a.x && y == a.y); }
    bool operator !=(const Cell& a) const { return !(*this == a); }

    int x;
    int y;
};

struct Shift
{
    Shift(int dx=0, int dy=0) : dx(dx), dy(dy) {}
    int dx, dy;
};

enum class Direction
{
    up, down, left, right
};

enum Figure_Type { I, J, L, O, S, T, Z };

class Figure
{
public:
    /* CONSTRUCTORS */
    Figure();
    Figure(Figure_Type);

    /* MOVEMENT */
    bool        Move(std::vector<Cell>&, Direction&);
    void        Drop(std::vector<Cell>&);
    bool        Rotate(std::vector<Cell>&);

    /* OTHER */
    void        Draw(HDC&);

private:

    /* METHODS */
    void        Generate();
    void        GenerateMasks();
    void        GenerateFigure();
    Figure      GetFigureCopy() const;

    /* DATA */
    char        mask[4][4];
    std::vector<Cell> vCells;
    Figure_Type  type;
    int         rotation;
    Shift       shift;
};

#endif

/*
 * And I'm getting exceptions on vCells.clear() method and (if I comment first
 * line) vCells.push_back(cell) line. Actually every operation with vector /
 * vector iterators crash my program even incrementing iterator, those are just
 * the first so my code isn't running any longer after them.
 *
 * Exception text:
 * **"Unhandled exception at 0x5A4ACCD2 (msvcp110d.dll) in
 *    Tetris_completely_new.exe: 0xC000041D: An unhandled exception was
 *    encountered during a user callback."**
 *
 * And these exceptions are thrown on 217's line of "xutility". I commented it:
 *
 *   ....
 *   // MEMBER FUNCTIONS FOR _Container_base12
 *   inline void _Container_base12::_Orphan_all()
 *     { // orphan all iterators
 *    #if _ITERATOR_DEBUG_LEVEL == 2
 *     if (_Myproxy != 0)
 *       { // proxy allocated, drain it
 *       _Lockit _Lock(_LOCK_DEBUG);
 *
 *       for (_Iterator_base12 **_Pnext = &_Myproxy->_Myfirstiter;
 *         *_Pnext != 0; *_Pnext = (*_Pnext)->_Mynextiter)
 *         **(*_Pnext)->_Myproxy = 0;**    // <------------ THIS LINE
 *       _Myproxy->_Myfirstiter = 0;
 *       }
 *    #endif // _ITERATOR_DEBUG_LEVEL == 2
 *     }
 *   ....
 *
 * Here is how my **Cell struct** looks like:
 */

//And **Figure constructor**:

Figure::Figure()
  : mask {{0}},
    vCells(),
    type((Figure_Type) (rand() % 7)),
    rotation(0),
    shift({0,0})
{
    Generate();
}

//My constructors are using Generate() method, which code is:
void Figure::Generate()
{
    GenerateFigure();
}

void Figure::GenerateFigure()
{
    vCells.clear();
    for(int y = 0; y < 4; y++) {
        for(int x = 0; x < 4; x++) {
            if(mask[y][x] == '0')
                vCells.push_back({4 + x + shift.dx, 20 - y + shift.dy});
        }
    }
}

int main()
{
    srand(time(0));
    Figure fig1;
    Figure fig2;
}