声明和原型差异 [英] Declaration and prototype difference

问题描述

在C语言中声明和原型之间有什么区别?在什么情况下它们称为声明，在哪些原型中?

What is the difference between declaration and prototype in C? In which situations they are called declarations and in which prototypes?

推荐答案

TL; DR; 所有原型都是声明，但并非所有声明都是原型.

TL;DR; All prototypes are declarations, but not all declarations are prototypes.

声明是标准中使用的通用术语， prototype 更具体.

Declaration is the generic terminology used in the standards, prototype is more specific.

引用C11，第6.7节

声明指定一组标识符的解释和属性. [...]

A declaration specifies the interpretation and attributes of a set of identifiers. [...]

以及第6.7.6节

每个声明器声明一个标识符，并在相同的操作数时断言 声明符出现在表达式中时的形式，它用 范围，存储期限和声明说明符指示的类型.

Each declarator declares one identifier, and asserts that when an operand of the same form as the declarator appears in an expression, it designates a function or object with the scope, storage duration, and type indicated by the declaration specifiers.

另一方面，来自第6.2.1章

On the other hand, from chapter §6.2.1

[....] 一个功能 prototype是函数的声明，该函数声明其参数的类型.

[....] A function prototype is a declaration of a function that declares the types of its parameters.

因此，一个衬里，原型是声明的更完整的形式(包括参数的类型).

So, one liner, prototype is more complete form (including types of parameter) of declaration.

关于标识符":第6.4.2.1节，

About "identifier": chapter §6.4.2.1,

标识符是一系列非数字字符(包括下划线_， 小写和大写拉丁字母，以及其他字符)和数字 6.2.1中描述的一个或多个实体. [...]

An identifier is a sequence of nondigit characters (including the underscore _, the lowercase and uppercase Latin letters, and other characters) and digits, which designates one or more entities as described in 6.2.1. [...]

以及第6.2.1章

标识符可以表示一个对象；功能;标签或结构，并集或成员 枚举typedef名称；标签名称；宏名称；或宏参数. [....]

An identifier can denote an object; a function; a tag or a member of a structure, union, or enumeration; a typedef name; a label name; a macro name; or a macro parameter. [....]

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