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列表迭代器访问冲突

发布于 2024-11-04 02:19:57 字数 1499 浏览 4 评论 0原文

我有一个指向 Main 类中的 SomeClass 对象的列表。在 Main 中，我可以使用 list::begin() 和 list::end() 迭代 list >。

当我从 SomeClass 的实例执行相同操作时（请记住 list 是 Main 类的公共成员），我得到了以下异常：

0xC0000005：读取位置 0xbaadf0ad 时访问冲突。

我对 C++ 编码相当陌生，有 Python 背景，所以如果有些内容没有意义，我深表歉意。

以下是这种情况的示例：

编辑： Main 类代码实际上不在构造函数内，而是在名为 InitialiseObjects() 的方法中。

编辑：异常来自 list::being() 方法中的行 return (iterator(_Nextnode(_Myhead), this));

#include <list>
using namespace std;

class Main
{
public:
    Main::InitialiseObjects()
    {
        // Execution starts here
        SomeClass someClass = new SomClass(this);
        someClasses.push_back(someClass);

        // This works fine
        for (list<SomeClass*>::iterator it = someClasses.begin(); it != someClasses.end(); it++)
            ...

        someClass->AFunction();
    }
    list<SomeClass*> someClasses;
}

class SomeClass
{
public:
    SomeClass::SomeClass(Main *main) : main(main) {}
    void SomeClass::AFunction()
    {
        // This will not work throwing the aformentioned error
        for (list<SomeClass*>::iterator it = main->someClasses.begin(); it != main->someClasses.end(); it++)
            ...
    }
private:
    Main *main;
}

原文

I have a list of pointers to SomeClass objects in a Main class. Whilst in Main I can iterate over the list using list::begin() and list::end().

When I do the same from an instance of SomeClass (bearing in mind that the list is a public member of the Main class) I get the following exception:

0xC0000005: Access violation reading location 0xbaadf0ad.

I am fairly new to coding in C++ coming from a Python background, so I apologise if something doesn't make sense.

Here is an example of the situation:

EDIT: The Main class codes is not actually inside the constructor, its in a method called InitialiseObjects().

EDIT: The exceptions comes from within the list::being() method with the line return (iterator(_Nextnode(_Myhead), this));

#include <list>
using namespace std;

class Main
{
public:
    Main::InitialiseObjects()
    {
        // Execution starts here
        SomeClass someClass = new SomClass(this);
        someClasses.push_back(someClass);

        // This works fine
        for (list<SomeClass*>::iterator it = someClasses.begin(); it != someClasses.end(); it++)
            ...

        someClass->AFunction();
    }
    list<SomeClass*> someClasses;
}

class SomeClass
{
public:
    SomeClass::SomeClass(Main *main) : main(main) {}
    void SomeClass::AFunction()
    {
        // This will not work throwing the aformentioned error
        for (list<SomeClass*>::iterator it = main->someClasses.begin(); it != main->someClasses.end(); it++)
            ...
    }
private:
    Main *main;
}

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唐婉 2024-11-11 02:19:57

0xC0000005: Access violation reading location 0xbaadf0ad.

我认为那是0xbaadf00d，直到您覆盖其中的某些内容，这表明未初始化的堆内存。那么，也许您正在取消引用不存在的 Main* ？例如，如果 main 尚未初始化，main->someClasses.begin() 可能会抛出异常。
事实上，这就是您的代码中的问题。 someClass->AFunction(); 当您位于 Main 构造函数内时调用该函数。因此，this 尚未完全有效，因此您无法在 AFunction 内使用它。

0xC0000005: Access violation reading location 0xbaadf0ad.

I think that was 0xbaadf00d until you overwrote something in it, which indicates uninitialized heap memory. So, maybe you're dereferencing a non-existant Main*? E.g. main->someClasses.begin() may throw your exception, if main wasn't initialized yet.
And indeed, this is the problem in your code. someClass->AFunction(); calls the function while you're inside the Main-constructor. As such, this will not be completely valid yet, so you can't use it inside the AFunction.