void *从函数 - 堆损坏返回的指针 [英] void* pointer returned from Function - Heap Corruption

问题描述

以前，我只是使用malloc处理这些类型的__out函数参数，但是我试图改变我的方式。

在管理原始输入的类中，GetRawInputDeviceInfo（）原型如下：

  UINT GetRawInputDeviceInfo（HANDLE，UINT，LPVOID，PUINT ）
  

LPVOID是指向包含所需信息的缓冲区的指针。 PUINT是指向包含由LPVOID指向的缓冲区中的数据大小的UINT的指针。

通常，我会（一旦填充PUINT）：

  PUINT cbSize; //假设它的大小正确，包含正确的
 //数据长度
 
 LPVOID buffer =（LPVOID）malloc（sizeof（& cbSize））; 
 GetRawInputDeviceInfo（XXX.handle，RIDI_DEVICENAME，buffer，cbSize）; 
 //做某事w /缓冲
 free（buffer）; 
  

现在，试图这样做没有malloc，我会写：
（对不起，

  PUINT cbsize; //假设它的大小正确并包含正确的
 //数据长度
  

1以下声明和使用示例：
LPVOID unique_ptr：

  std :: unique_ptr< LPVOID>缓冲; 
 GetRawInputDeviceInfo（xxx.handle，RIDI_DEVICENAME，buffer.get（），
 cbSize）; 
  

UINT unique_ptr：

  std :: unique_ptr< UINT>缓冲; 
 GetRawInputDeviceInfo（xxx.handle，RIDI_DEVICENAME，
（LPVOID）buffer.get（），cbSize）; 
  

Raw UINT指针：

  UINT * buffer = NULL; 
 GetRawInputDeviceInfo（xxx.handle，RIDI_DEVICENAME，
（LPVOID）buffer，cbSize）; 
  

然后读取缓冲区：

  OutputDebugString（（LPCSTR）buffer）//为unique_ptr添加.get（）
  

事情是，缓冲区包含我想要的信息，它的输出应该是！但是，当unique_ptr超出范围并被删除（或UINT *被删除），我得到一个堆的腐败异常。我走过代码，发生了什么是一旦GetRawInputDeviceInfo函数运行，我所有的类级容器/变量都有他们的数据重写。例如，上面的序列出现在一个for循环中，我的迭代器从0（第一次迭代）到80837436（大约），所有其他变量局部变量被弄乱了。

那么，我如何检索缓冲区中的信息，而不用将其他所有东西都拧紧呢？最好不要使用malloc / free，而要使用RAII的精神：

解决方案

使用 GetRawInputDeviceInfo 是

1. 获取名称所包含的字符数

     UINT char_count; 
    GetRawInputDeviceInfo（xxx.handle，RIDI_DEVICENAME，NULL，& char_count）; 
     




2. 分配足够长的字符串缓冲区，并检索名称

     std :: unique_ptr< wchar_t []> buf（new wchar_t [char_count]）; 
    GetRawInputDeviceInfo（xxx.handle，RIDI_DEVICENAME，buf.get（），& char_count）; 
     

您的范例程式码不会造成堆损坏。可能你的真正的代码使用一个未初始化的 buffer ，这导致GetRawInputDeviceInfo写入数据到一些非预期的位置。

Previously, I'd just dealt with these types of __out function parameters using malloc, but I'm trying to change my ways.

As a specific example, in a class to manage Raw Input, GetRawInputDeviceInfo() is prototyped as such:

UINT GetRawInputDeviceInfo(HANDLE, UINT, LPVOID, PUINT)

LPVOID is a pointer to a buffer containing the information I need. PUINT is a pointer to a UINT containing the size of data contained in the buffer pointed to by LPVOID.

Normally, I would (once I have populated the PUINT):

PUINT cbSize; // assume it is sized correctly and contains the proper
              // length of data

LPVOID buffer = (LPVOID)malloc(sizeof(&cbSize));
GetRawInputDeviceInfo(XXX.handle, RIDI_DEVICENAME, buffer, cbSize);
//do something w/buffer
free(buffer);

Now, attempting to do this without malloc, I would write: (sorry, I'm typing this from work, so I may botch this from memory)

PUINT cbsize; // assume it is sized correctly and contains the proper
              // length of data

1 of the following declaration and use examples: LPVOID unique_ptr:

std::unique_ptr<LPVOID> buffer;
GetRawInputDeviceInfo(xxx.handle, RIDI_DEVICENAME, buffer.get(),
                      cbSize);

UINT unique_ptr:

std::unique_ptr<UINT> buffer;
GetRawInputDeviceInfo(xxx.handle, RIDI_DEVICENAME,
                      (LPVOID)buffer.get(), cbSize);

Raw UINT Pointer:

UINT *buffer = NULL;
GetRawInputDeviceInfo(xxx.handle, RIDI_DEVICENAME,
                      (LPVOID)buffer, cbSize);

Then reading the buffer:

OutputDebugString((LPCSTR)buffer) //add .get() for unique_ptr

The thing is, the buffer contains the information I want, and it's outputted as it should be! However, when the unique_ptr goes out of scope and is deleted (or the UINT* is deleted), I get a Heap Corruption exception. I stepped through the code and what happens is once the GetRawInputDeviceInfo function runs, ALL of my class level containers/variables have their data rewritten. For example, the above sequence appears in a for loop, and my iterator goes from 0 (first iteration) to 80837436 (or so), and all other variables local variables are messed up.

So, how can I retrieve the information in the buffer without screwing everything else up? And preferably without using malloc/free, and with the spirit of RAII :)

解决方案

The correct way to use GetRawInputDeviceInfo is

1. Get the number of characters the name contains

   UINT char_count;
   GetRawInputDeviceInfo(xxx.handle, RIDI_DEVICENAME, NULL, &char_count);
   

2. Allocate a long enough string buffer, and retrieve the name

   std::unique_ptr<wchar_t[]> buf (new wchar_t[char_count]);
   GetRawInputDeviceInfo(xxx.handle, RIDI_DEVICENAME, buf.get(), &char_count);
   

Your example code won't cause heap corruption. Probably your real code uses an uninitialized buffer, which caused GetRawInputDeviceInfo to write data to some unintended location.

这篇关于void *从函数 - 堆损坏返回的指针的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！