Question

Visual Studio 2010

当我为char字符串分配内存时，将字符串（指针）传递给函数，然后尝试释放内存，我得到“Heap Corruption Detected”运行时错误。< / p>

我怀疑这是该函数在返回后将内存标记为“已释放”的结果，但我仍然对如何解决这个问题感到困惑。只是删除对free（）的调用我感觉不舒服。

// this function takes a char string, converts it to a wide char string, 
// then passes the converted string to another function.
void Class::WriteToLog(const char * msg)
{
    // allocate memory
    wchar_t * wMsg = (wchar_t*)malloc((strlen(msg) * sizeof(wchar_t)) + 1); // add one for null terminating char
    // convert to wide char. This works fine, and returns 4 when msg is 4 chars long.
    numChar = MultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, msg, strlen(msg), wMsg, strlen(msg));

    wMsg[numChar] = L'\0'; // terminate string
    // At this point wMsg contains the same thing msg contains. Works fine.
    WriteToLogW(wMsg); // Works fine. Writes the string to a text file.
    free(wMsg); // Heap Corruption Detected
}


void Class::WriteToLogW(const wchar_t * msg)
{
    ...
}

Answer 1

您在+1末尾添加的malloc只会在使用char时为空终结符分配足够的内存，因为char是1个字节（因此空终止符将占用一个字节）。

由于您正在使用wchar_t，因此空终止符将占用sizeof(wchar_t)个字节，这几乎总是大于1.因此，malloc调用分配的内存不足。将您的malloc电话重新构建为如下所示：

wchar_t * wMsg = (wchar_t*) malloc((strlen(msg) + 1) * (sizeof(wchar_t));

这样，分配的总字节数为空终止符留出了空间。

Answer 2

即使是宽字符串的终止nul也很宽，所以只给它一个字节是不够的。变化：

wchar_t * wMsg = (wchar_t*)malloc((strlen(msg) * sizeof(wchar_t)) + 1);

到

wchar_t * wMsg = (wchar_t*)malloc((strlen(msg) + 1) * sizeof(wchar_t));

将指针传递给函数然后在指针上调用free（）时，“检测到堆腐败”

2 个答案: