在C和C结构之间的差异++ [英] Differences between struct in C and C++

问题描述

我想一个C ++结构转换为C，但不断收到未声明的标识符？请问c + +有指结构不同的语法？

I am trying to convert a C++ struct to C but keep getting "undeclared identifier"? Does C++ have a different syntax for referring to structs?

struct KEY_STATE 
{
    bool kSHIFT; //if the shift key is pressed 
    bool kCAPSLOCK; //if the caps lock key is pressed down
    bool kCTRL; //if the control key is pressed down
    bool kALT; //if the alt key is pressed down
};

我使用的另一种结构内部类型KEY_STATE的变量：

I am using a variable of type KEY_STATE inside another structure:

typedef struct _DEVICE_EXTENSION
{
    WDFDEVICE WdfDevice;
    KEY_STATE kState;
} DEVICE_EXTENSION, *PDEVICE_EXTENSION;

结果错误C2061：语法错误：标识符'KEY_STATE

...就行 KEY_STATE KSTATE; 我的WDK编译器建设，如果有什么差别。这是理所当然的头文件。我移植的C ++ WDM驱动程序WDF和C

...on the line KEY_STATE kState; I am building with the WDK compiler if that makes any difference. This is in a header file of course. I am porting C++ WDM driver to WDF and C.

这是MSDN文章C2061 。

这是初始化可以用括号括起来。为了避免这个问题，附上声明符在括号或使其一个typedef。

An initializer may be enclosed by parentheses. To avoid this problem, enclose the declarator in parentheses or make it a typedef.

当编译器检测到前pression作为类模板参数也可能导致此错误;使用typename告诉编译器它是一种类型。

This error could also be caused when the compiler detects an expression as a class template argument; use typename to tell the compiler it is a type.

更改KEY_STATE到typedef结构还是引起了这个错误，实际上导致了很多。有太多的括号内没有免费的括号或事物，那就是文章建议其他的事情。

Changing KEY_STATE to typedef struct still causes this error and actually causes a lot more. There are no free parentheses or things in too many parentheses, that is the other thing the article suggests.

推荐答案

在C，该类型的名称是结构KEY_STATE 。

In C, the name of the type is struct KEY_STATE.

所以，你必须声明第二结构为

So you have to declare the second struct as

typedef struct _DEVICE_EXTENSION
{
    WDFDEVICE WdfDevice;
    struct KEY_STATE kState;
} DEVICE_EXTENSION, *PDEVICE_EXTENSION;

如果你不想写结构所有的时间，你可以使用一个typedef申报 KEY_STATE 类似 DEVICE_EXTENSION ：

If you do not want to write struct all the time, you can use a typedef declare KEY_STATE similar to DEVICE_EXTENSION:

typedef struct _KEY_STATE
{
    /* ... */
} KEY_STATE;

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