LARGE_INTEGER和DUMMYSTRUCTNAME

问题描述

当我遇到LARGE_INTEGER的定义时.我发现一些问题:

When I come across the definition of LARGE_INTEGER. I find some questions:

typedef union _LARGE_INTEGER {
    struct {
        DWORD LowPart;
        LONG HighPart;
    } DUMMYSTRUCTNAME;
    struct {
        DWORD LowPart;
        LONG HighPart;
    } u;
    LONGLONG QuadPart;
} LARGE_INTEGER;

我们可以重写如下吗?

typedef union _LARGE_INTEGER {
    struct {
        DWORD LowPart;
        LONG HighPart;
    } DUMMYSTRUCTNAME;
    LONGLONG QuadPart;
} LARGE_INTEGER;

我认为结构u是重复的.那么，为什么MSVC这样实现LARGE_INTEGER?我想知道也许有些原因，例如兼容性.

I think the struct u is duplicate. So why MSVC implement LARGE_INTEGER as this? I wonder maybe some reason like compatibility.

推荐答案

显然，这是为了避免在联盟中具有匿名结构，这是一种调整.Visual C ++已支持此功能，但语言标准不允许这样做.(请参见无法理解LARGE_INTEGER结构，以了解没有DUMMYSTRUCTNAME .)将添加该名称，以使并集与标准C ++(可能与某种自动化工具)保持一致.

It is apparently an adjustment to avoid having an anonymous structure in a union. This had been supported by Visual C++, but is not allowed in by the language standard. (See can't make sense of LARGE_INTEGER struct for a declaration of the struct without the DUMMYSTRUCTNAME.) The name would have been added to bring the union into conformance with standard C++, possibly with some sort of automated tool.

最新版本 LARGE_INTEGER 完全摆脱了结构，只有 QuadPart .

Later versions of LARGE_INTEGER get rid of the structs entirely and just have the QuadPart.

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