GetMessage()函数是一个很常见的函数，如果使用SDK写过Windows程序的话，那么就更不陌生，该函数的返回值值得注意的地方，因为最近在看Win32汇编的书，书中提到了这个函数。但是发现对于该函数的判断也是不对的。把MSDN上对该函数的返回值的介绍留在这里吧。MSDN中的内容都是英文的，不过还是比较好理解的。
以下摘自微软的MSDN：
Return Values
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.
Warning Because the return value can be nonzero, zero, or -1, avoid code like this:
while (GetMessage( lpMsg, hWnd, 0, 0)) ...
The possibility of a -1 return value means that such code can lead to fatal application errors. Instead, use code like this:
BOOL bRet;
while( (bRet = GetMessage( &msg, NULL, 0, 0 )) != 0)
{
if (bRet == -1)
{
// handle the error and possibly exit
}
else
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}