DrawText绘制的文本框出现了奇怪字符

代码如上图，请问下图啦字后面那一坨奇怪字符是怎么回事？如何解决?

sizeof(buf)
应改为
wcslen(buf)
或
5
或
-1

DrawText
The DrawText function draws formatted text in the specified rectangle. It formats the text according to the specified method (expanding tabs, justifying characters, breaking lines, and so forth).

int DrawText(
HDC hDC, // handle to device context
LPCTSTR lpString, // pointer to string to draw
int nCount, // string length, in characters
LPRECT lpRect, // pointer to struct with formatting dimensions
UINT uFormat // text-drawing flags
);

Parameters
hDC
Handle to the device context.
lpString
Pointer to the string to be drawn. If the nCount parameter is –1, the string must be null-terminated.
If uFormat includes DT_MODIFYSTRING, the function could add up to four additional characters to this string. The buffer containing the string should be large enough to accommodate these extra characters.

nCount
Specifies the number of characters in the string. If nCount is –1, then the lpString parameter is assumed to be a pointer to a null-terminated string and DrawText computes the character count automatically.