为什么 :: (scope) 与空的左侧操作数一起使用?

2022-01-04 00:00:00 scope operator-keyword c++

我已经看过几次了，我一直在挠头想知道为什么...

I've seen this a few times now, and I've been scratching my head wondering why...

例如:(http://www.codeguru.com/forum/showthread.php?t=377394)

As an example: (http://www.codeguru.com/forum/showthread.php?t=377394)

void LeftClick ( )
{  
  INPUT    Input={0};
  // left down 
  Input.type      = INPUT_MOUSE;
  Input.mi.dwFlags  = MOUSEEVENTF_LEFTDOWN;
  ::SendInput(1,&Input,sizeof(INPUT));

  // left up
  ::ZeroMemory(&Input,sizeof(INPUT));
  Input.type      = INPUT_MOUSE;
  Input.mi.dwFlags  = MOUSEEVENTF_LEFTUP;
  ::SendInput(1,&Input,sizeof(INPUT));
}

这个例子在没有 ::(范围)运算符的情况下工作，为什么它们甚至在那里?

This example works without the :: (scope) operators so why are they even there?

推荐答案

这基本上意味着获取 GLOBAL 作用域函数，而不是当前可见的函数".

This basically mean "get the GLOBAL scoped function, instead of the currently visible one".

void SendInput() { /* (1) */
}

namespace derp {
    void SendInput() { /* (2) */
    }

    void LeftClick() {
        ...
        ::SendInput(); /* matches (1) */
        SendInput();  /* matches (2) */
    }
}

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