为什么“struct"关键字必须在 C 中的 struct 实例之前? [英] Why must the 'struct' keyword precede struct instances in C?

问题描述

假设我在 C 中定义了一个结构体.如果我声明了该结构体的一个实例，则必须在其前面包含 'struct' 关键字.

Let's say I define a struct in C. If I declare an instance of that struct, it's necessary that I include the 'struct' keyword in front of it.

// Define struct
struct Book {
   char title[50];
   char author[50];
   char subject[100];
   int book_id;
};

// Instantiate struct
int main()
{
    struct Book myBook;
}

我的问题:为什么 struct 关键字必须先于结构的任何实例化?似乎编译器会有大量信息来推断Book"是一个结构体.

My question: why is it necessary for the struct keyword to precede any instantiation of the struct? It seems like the compiler would have plenty of information to deduct that 'Book' is a struct.

我知道你可以通过使用 typedef 来解决这个问题，但这真的只是编译器应该已经知道的东西的样板代码.

I realize you can get around this by using a typedef, but that really just seems like boiler plate code for something the compiler should already know.

推荐答案

由于使用关键字 struct、union 和 enum 名称，这些类型可以形成自己的命名空间，不会与其他实体的名称冲突.

Due to using the keywords struct, union and enum names for these types can form their own namespace that will not conflict with names of other entities.

例如

#include <stdio.h>

int main(void) 
{
    struct Book 
    {
        const char *Book;
    } Book = { "The first favorite book" };

    struct Book otherBook = { .Book = "The second favorite book" };

    puts( Book.Book );
    puts( otherBook.Book );

    return 0;
}

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