这个函数虽然返回值类型是BOOL,但是还有可能返回-1 !
Return Value
BOOL
If the function retrieves a message other than WM_QUIT , the return value is nonzero.
If the function retrieves the WM_QUIT message, the return value is zero.
If there is an error, the return value is -1. For example, the function fails if hWnd is an invalid window handle or lpMsg is an invalid pointer. To get extended error information, call GetLastError .
Because the return value can be nonzero, zero, or -1, avoid code like this:
The possibility of a -1 return value means that such code can lead to fatal application errors. Instead, use code like this: