关于C#：初始化结构中的第一个元素


Initializing the first element in a struct

我用C语言进行了很多Win32编程，许多Win32结构都有一个'size'(通常称为cbSize或length)成员作为第一个元素，需要在进行相关API调用之前进行设置。例如：

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WINDOWPLACEMENT wp;
wp.length = sizeof(WINDOWPLACEMENT);
GetWindowPlacement(hWnd, &wp);

现在，我认为将结构成员初始化为零是一种很好的做法，我可以使用：

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WINDOWPLACEMENT wp = { };

或

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WINDOWPLACEMENT wp = { 0 };

但是，如果我像这样初始化第一个成员，该结构的其他成员会怎样：

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WINDOWPLACEMENT wp = { sizeof(WINDOWPLACEMENT) };

它们是否自动初始化为零？还是取决于我使用的是哪个编译器以及它是否为调试版本？

是的，它们会自动初始化为零。

8.5.1 / 7：

If there are fewer initializers in the
list than there are members in the
aggregate, then each member not
explicitly initialized shall be
value-initialized (8.5). [Example:

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struct S { int a; char* b; int c; };
S ss = { 1,"asdf" };

initializes ss.a with 1, ss.b with
"asdf", and ss.c with the value of an
expression of the form int(), that is,
0. ]

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如果您确定尺寸是第一个元素，则可以。在初始化器中未获取值的所有成员将被清零。

此：

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WINDOWPLACEMENT wp = { X };

将所有剩余成员初始化为0(假设POD)。

请参阅：8.5.1聚合[dcl.init.aggr]段落：7：

7 If there are fewer initializer-clauses in the list than there are members in the aggregate, then each member not explicitly initialized shall be value-initialized (8.5).

[ Example:

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   struct S { int a; char* b; int c; };
   S ss = { 1,"asdf" };

initializes ss.a with 1, ss.b with"asdf", and ss.c with the value of an expression of the form int(), that
is, 0. —end example ]

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