free() 调用中的 _snwprintf_s 堆损坏错误 [英] _snwprintf_s heap corruption error in free() call

问题描述

我正在尝试使用 _snwprintf_s 来连接两个字符串.我还想在每个字符串后附加 \r\n.

I am trying to use _snwprintf_s to concatenate two strings. I also want to append \r\n after each string.

所以我分配了一个 wchar 缓冲区，最初包括两个字符串的 \r\n 和 null.我试着一个接一个地打印.

So I allocate a wchar buffer initially including the \r\n and null for both strings. I try to print one after the other.

我看到两个字符串都被写入了.但是当尝试释放(wbuff)时，它会给我一个堆损坏"错误.我不知道我在哪里越界了.

I see both strings are written. But when trying to free(wbuff), it throws me a "Heap corruption" error. I am not able to figure where I am crossing the bounds.

我哪里出错了?让我知道.谢谢

Where am I going wrong? Let me know. Thanks

int main()
{
    WCHAR* name1 = L"HelloWorld";
    WCHAR* name2 = L"GoodMorning";
    WCHAR* wbuff = NULL;
    int i = wcslen(name1) + wcslen(name2) + 6; //in words for size of buffer
    int out = 0;

    wbuff = (WCHAR*)malloc(i * sizeof(WCHAR));
    ZeroMemory(wbuff, i * sizeof(WCHAR));

    int prevLen = 0, currLen = 0;
    currLen = wcslen(name1) + 2; //in bytes

    out = _snwprintf_s(wbuff,i,currLen, L"%s\r\n", name1);

    printf("Wrote %d characters\n", out);

    prevLen = currLen;
    currLen = wcslen(name2) + 2;


    out = _snwprintf_s((wbuff+prevLen),i,currLen, L"%s\r\n", name2);

    printf("Wrote %d characters\n", out);

    printf("%S of sisze %u", wbuff, wcslen(wbuff));


    free(wbuff);

    printf("memory freed\n");       

}

推荐答案

_snwprintf_s 用 fefe 标记填充缓冲区中的剩余字符.我在文档中找不到这个，但我可以在调试器中看到它.因此，您的第二个 _snwprintf_s 表示它有 i 字符可用，但您的起始位置是 prevLen 个字符.修复 i 以进行偏移调整.

_snwprintf_s fills up the remaining characters in the buffer with an fefe marker. I can't find this in the documentation, but I can see it in the debugger. Hence, your second _snwprintf_s is indicating it's got i characters available, but your start position is prevLen chars into it. Fix i to have the offset adjustment as well.

取而代之的是:

out = _snwprintf_s((wbuff+prevLen),i,currLen, L"%s\r\n", name2);

这个:

out = _snwprintf_s((wbuff+prevLen),i-prevLen,currLen, L"%s\r\n", name2);

_snwprintf_s 会用标记填满整个缓冲区

_snwprintf_s will fill up the entire buffer with markers

取而代之的是:

printf("%S of sisze %u", wbuff, wcslen(wbuff));

这个:

printf("%ls of sisze %u", wbuff, (unsigned int)(wcslen(wbuff)));

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