在自定义堆上设置内存 [英] Setting memory on a custom heap

问题描述

是否可以从HeapCreate（）获取堆句柄，并将所有可用内存设置为某个值？

Is it possible to take a heap handle from HeapCreate() and set all available memory to a certain value?

我已经尝试按区域枚举堆设置它的方式，但我得到访问违反。

I've tried enumerating the heap by region and setting it that way, but I get access violations.

我基本上想设置我的堆中的内存为一个自定义值，我可以用于调试，通过HeapDestroy销毁。

I basically want to set the memory in my heap to a custom value that I can use for debugging, before it's ultimately destroyed via HeapDestroy.

推荐答案

简短的回答是不，你不能填充堆一个特定的值。

The short answer is "no, you can't fill the heap with a specific value".

您可以使用调试版本封装堆访问函数，例如

You could wrap your heap access functions with debug versions, for example

// In some header file
#define HeapAlloc(a, b, c) MyHeapAlloc(a, b, c, __FILE__, __LINE__)
#define HeapFree(a, b, c) MyHeapFree(a, b, c, __FILE__, __LINE__)

... 

// In a separate source file:

#ifdef HeapAlloc
#undef HeapAlloc
#undef HeapFree
#endif

struct extra
{
    extra *next;
    size_t size;
    const char *file;
    int line;
};

extra* head;

LPVOID MyHeapAlloc(HANDLE heap, DWORD flags, SIZE_T size, const char *file, int line)
{
    LPVOID res = HeapAlloc(heap, flags, size + sizeof(extra));
    if (!res)
    {
        cout << "Allocation failed, called from " << file << ":" << line << endl;
        return 0;
    }

    extra *p = reinterpret_cast<extra*>(res);
    res = reinterpret_cast<void*>(&p[1]); 

    p->next = head;
    p->size = size;
    p->file = file;
    p->line = line;

    memset(res, 0xAA, size); 
    return res;
}

BOOL MyHeapFree(HANDLE heap, DWORD flags, LPVOID mem, const char *file, int line)
{
    extra *p = reinterpret_cast<extra*>(mem);
    p = reinterpret_cast<void*>(&p[-1]); 

    extra *q = head;
    extra *prev = 0;
    while(q)
    {
        if (reinterpret_cast<void*>(&q[1]) == mem)
        {
            break;
        }
        prev = q;
        q = next;
   }
   if (!q)
   {
       cout << "Attempt to free memory that wasn't allocated from " << file << ":" << line << endl;
       return false; 
   }

   /* Unlink q - if prev = NULL then it's the first one, so just move head */
   if (prev)
   {
      prev->next = q->next;
   }
   else
   {
      head = q->next;
   }

   memset(mem, 0xBB, q->size);
   return HeapFree(heap, flags, reinterpret_cast<void *>(q); 
}

我已经输入了所有的内容，所以可能有小的打字错误，但希望它显示一个处理内存分配的方法。在某些情况下，你可能需要填充 struct为16或32个字节的倍数，以确保以下数据的对齐。当然，可以随时转储 head ，查看分配的内容。

I have just typed all that in, so there may be minor typos, but hopefully it shows you a method of dealing with memory allocations. For some case, you may have to pad the extra struct to be a multiple of 16 or 32 bytes to ensure alignment of the following data. You can of course, at any time, dump the linked list pointed to by head, to see what is allocated.

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