求助！C++获取鼠标位置的代码执行异常！？

Question

如图所示，X = LOWORD(lParam);和Y =HIWORD(lParam);，这两行代码放到一个块中，不论顺序如何，只是执行了上面的，跳过下面的，即使都是LOWORD或都是HIWORD也是如此，右下角的变量变化说明了一切！请大家指教这到底是什么情况？怕是我学了假的C++哦。。。。。。心态爆炸

Answer 1

应该用：

xPos = GET_X_LPARAM(lParam); 
yPos = GET_Y_LPARAM(lParam); 

如下引用自https://msdn.microsoft.com/en-us/library/windows/desktop/ms645607(v=vs.85).aspx

Do not use the LOWORD or HIWORD macros to extract the x- and y- coordinates of the cursor position because these macros return incorrect results on systems with multiple monitors. Systems with multiple monitors can have negative x- and y- coordinates, and LOWORD and HIWORD treat the coordinates as unsigned quantities.