访问冲突写入位置 0xcccccccc [英] Access violation writing location 0xcccccccc

问题描述

在过去的 2 天里，我一直被一个似乎无法摆脱的违规行为所困扰.我使用了断点并找到了错误所在，但我只是希望你们中的一个人知道问题所在，而不必复制+粘贴我的所有代码 -.-

我要了

<块引用><块引用>

Escape.exe 中 0x1027cb1a (msvcr100d.dll) 处的第一次机会异常:0xC0000005:访问冲突写入位置 0xcccccccc.Escape.exe 中 0x1027cb1a (msvcr100d.dll) 处未处理的异常:0xC0000005:访问冲突写入位置 0xcccccccc.

现在，快速的谷歌搜索让我觉得发生了一些奇怪的事情.所有搜索结果都在谈论实际上并未指向任何地方的指针(0xcccccccc 是低内存地址?).

我还没有在我的代码中使用指针，但无论哪种方式，我都会粘贴函数并指出抛出异常的行(粗体):

void mMap::fillMap(){for(int i = 0; i <= 9; i++){for(int z = 0; z <= 19; z++){瓷砖 t1;//默认图块类型 = "NULLTILE"myMap[i][z] = t1;}}}

现在 myMap 是一个 Tile 类型的二维数组.几天前我有这个工作，直到我添加了一些其他类，它都停止工作了！

解决方案

一个未初始化的指针，或者一个存储在内存中已被释放的指针.我认为 cccccccc 是第一个，cdcdcdcd 是第二个，但它因编译器/库实现而异.

对于您的特定代码，可能 myMap 尚未分配，那么 myMap[0][0] 将导致对 0xcccccccc 的访问尝试.

<小时>

也可能发生 myMap 是您的类的开头，并且类指针未初始化:

类mMap{平铺 myMap[10][20];民众:void f() { myMap[0][0] = 0;}};mMap*什么；什么-> f();//什么是无效指针

发生这种情况是因为成员函数不是虚拟的，所以编译器知道要运行什么代码并将对象指针作为隐藏参数传递.最终编译器会发出如下计算:

this + offsetof(Whatever::myMap) + z * sizeof(myMap[0]) + i * sizeof(myMap[0][0])

this 未初始化，是 0xcccccccc.显然 offsetof 部分为零，并且 i 和 z 在第一次循环中都为零，所以你得到 0xcccccccc +0 + 0 + 0 作为内存地址.

<小时>

要对此进行调试，请使用调用堆栈并找到调用 fillMap 的函数.然后检查用于成员访问的指针 (->) 来自的那个函数.

For the past 2 days I've been stuck on a violation which I can't seem to get to go away. I've used break points and located where the error is, but I'm just hoping one of you will know what the issue is without me having to copy+paste all my code -.-

I'm getting

First-chance exception at 0x1027cb1a (msvcr100d.dll) in Escape.exe: 0xC0000005: Access violation writing location 0xcccccccc. Unhandled exception at 0x1027cb1a (msvcr100d.dll) in Escape.exe: 0xC0000005: Access violation writing location 0xcccccccc.

Now, a quick google search makes me think there's something peculiar going on. All the search results talk about pointers not actually pointing anywhere (0xccccccccc is a low memory address?).

I'm yet to use pointers in my code but either way I'll paste the function and point out the line the exception gets thrown (in bold):

void mMap::fillMap(){
    for(int i = 0; i <= 9; i++){
        for(int z = 0; z <= 19; z++){
            Tile t1;    // default Tile Type = "NULLTILE"
            myMap[i][z] = t1;
        }
    }
}

Now myMap is a 2d array of type Tile. I had this working a couple of days ago until I added some other classes and it all stopped working!

解决方案

Either an uninitialized pointer, or a pointer stored in memory that's been freed. I think cccccccc is the first and cdcdcdcd is the second, but it varies with compiler/library implementation.

For your particular code, probably myMap hasn't been allocated yet, then myMap[0][0] would result in an access attempt to 0xcccccccc.

---

It can also happen that myMap is the beginning of your class, and the class pointer was uninitialized:

class mMap
{
     Tile myMap[10][20];
public:
     void f() { myMap[0][0] = 0; }
};

mMap* what;
what->f(); // what is an invalid pointer

This happens because the member function is not virtual, so the compiler knows what code to run and passes the object pointer as a hidden parameter. Eventually the compiler emits a calculation like:

this + offsetof(Whatever::myMap) + z * sizeof(myMap[0]) + i * sizeof(myMap[0][0])

this, being uninitialized, is 0xcccccccc. Evidently the offsetof part is zero, and i and z are both zero the first time through your loop, so you get 0xcccccccc + 0 + 0 + 0 as the memory address.

---

To debug this, use the call stack and find the function that called fillMap. Then check in that function where the pointers used for member access (->) came from.

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