释放void指针 [英] freeing a void pointer

问题描述

如何释放void指针。

  struct vStruct {
 void * vPtr; 
 struct vStruct * next; 
}; 
 
 struct vStruct sObj; 
 struct vStruct * sObjNew = sObj; 
 
 delete sObjNew-> vPtr; ----------->这是正确的方法删除void指针
 delete sObjNew; 
  

显示错误运算符'delete'，应用于具有未定义行为的void *

解决方案

您不应该删除 void 指针。 delete 适用于特定类型（因此编译器知道应该调用哪个析构函数 - 如错误消息中所述）。

  class DataWrapper 
如果您想在结构中保留未指定的类型， {
 public：
 virtual void * GetData（）= 0; 
 virtual〜DataWrapper（）
 {
} 
}; 
 
 class MyDataWrapper 
 {
 protected：
 MyData * data; 
 
 public：
 MyDataWrapper（MyData * newData）
 {
 data = newData; 
} 
 
 void * GetData（）
 {
 return data; 
} 
 
〜MyDataWrapper（）
 {
 delete data; 
} 
}; 
 
 struct vStruct 
 {
 MyDataWrapper * vPtr; 
 struct vStruct * next; 
 
〜vStruct（）
 {
 if（vPtr！= null）
 delete vPtr; 
} 
}; 
 
 vStruct sObj; 
 sObj.vPtr = new MyDataWrapper（new MyData（））; 
 
 //当sObj被删除时，MyDataWrapper被
 //删除（由于〜vStruct）和
 //生效，分配的数据也被删除。 
  

注意，这是一个简单的例子，它可以更美观地写。

How to free a void pointer.

struct vStruct {
    void *vPtr;
    struct vStruct *next;
};

struct vStruct sObj;
struct vStruct *sObjNew = sObj;

delete sObjNew->vPtr; -----------> Is this correct way to delete void pointer
delete sObjNew;

Showing error Operator 'delete', applied to void* argument having has undefined behavior, and most likely does not invoke the object's destructor.

解决方案

You should not delete a void pointer. delete works for specific types (such that compiler knows, which destructor should be called - as stated in error message).

If you want to hold unspecified type in your structure, you have to wrap it somehow.

class DataWrapper
{
public:
    virtual void * GetData() = 0;            
    virtual ~DataWrapper()
    {
    }
};

class MyDataWrapper
{
protected:
    MyData * data;

public:
    MyDataWrapper(MyData * newData)
    {
        data = newData;
    }

    void * GetData()
    {
        return data;
    }

    ~MyDataWrapper()
    {
        delete data;
    }
};

struct vStruct
{
    MyDataWrapper * vPtr;
    struct vStruct *next;

    ~vStruct()
    {
        if (vPtr != null)
            delete vPtr;
    }
};

vStruct sObj;
sObj.vPtr = new MyDataWrapper(new MyData());

// When sObj gets deleted, MyDataWrapper is
// deleted too (thanks to the ~vStruct) and
// in effect, the allocated data is deleted too.

Note, that it's a simple example, it can be written more aesthetically.

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