CString getbuffer and releasebuffer instructions

Let's start with a piece of code ：

#include <atlstr.h>

// test CString

int main(int argc, _TCHAR* argv[])
{
	CStringA strTemp = "555";
	// The output here is 3, No terminator 
	printf("str=%s,len=%d\n",strTemp.GetBuffer(),strTemp.GetLength());

	LPSTR lpStr = strTemp.GetBuffer(10);
	// The output here is 3, Because of GetBuffer The return value of , Not invoked ReleaseBuffer,GetLength() The returned result will be incorrect 
	strcpy(lpStr,"666666");
	printf("str=%s,len=%d\n",strTemp.GetBuffer(),strTemp.GetLength());

	strTemp.ReleaseBuffer();
	// Because the call ReleaseBuffer,GetLength() The returned result is 6
	printf("str=%s,len=%d\n",strTemp.GetBuffer(),strTemp.GetLength());

	system("pause");
	return 0;
}

Running results ：

ReleaseBuffer Source code ：

   	void ReleaseBuffer(_In_ int nNewLength = -1)
	{