为什么一个typedef不能在内部结构允许吗？

问题描述

我有一个程序，定义了现有typedef结构中的typedef结构，我想知道为什么我收到一个编译错误。

I have a program that defines a typedef struct within an existing typedef struct, and I am wondering why I am getting a compilation error.

下面是程序：

typedef struct Outer
{
    typedef struct Inner
    {
        int b;
    }INNER;


    INNER inner;
    int a;

}OUTER;

int main()
{
    OUTER obj;
    obj.a = 10;
    obj.inner.b=8;
    return 0;
}

在编译时给出以下错误：

on compilation gives following error ::

test.c:3:5: error:expected specifier-qualifier-list before ‘typedef’
test.c: In function ‘main’:
test.c:17:5: error: ‘OUTER’ has no member named ‘a’
test.c:18:5: error: ‘OUTER’ has no member named ‘inner’

但是，当我改变了计划，以

but, when I changed the program to

typedef struct Outer
{
    struct Inner
    {
        int b;
    };

    struct Inner inner;
    int a;

 }OUTER;

 int main()
 {
    OUTER obj;
    obj.a = 10;
    obj.inner.b=8;
    return 0;
 }

它编译成功。

为什么不的typedef与内部结构允许吗？

Why is typedef not allowed with inner structures?

推荐答案

C没有允许存储类说明（的typedef ，也在一个结构成员的声明中静态或的extern ）。这是在结构和联合声明中6.7.2.1p1 C99中的语法规定。

C does not allow a storage-class specifier (typedef, but also static or extern) in the declaration of a structure member. This is specified in the syntax of structures and unions declaration in 6.7.2.1p1 in C99.

/* The compiler will issue a diagnostic for this declaration */
struct s {
    static int a;
};

您可以比较6.7.2.1p1语法声明的语法，其中的声明符不是函数参数或在6.7p1结构/联合成员，并看到，在这种情况下，存储类说明符是允许的。

You can compare 6.7.2.1p1 syntax with the syntax of a declaration where the declarator is not a function parameter or a structure / union member in 6.7p1 and see that in this case the storage-class specifiers are allowed.

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