“文件范围"和“文件范围"之间有什么区别?和“程序范围" [英] What is the difference between "File scope" and "program scope"

问题描述

据说全局声明的变量具有程序范围
用static关键字全局声明的变量被认为具有文件作用域.

A variable declared globally is said to having program scope
A variable declared globally with static keyword is said to have file scope.

例如:

int x = 0;             // **program scope**   
static int y = 0;      // **file scope**  
static float z = 0.0;  // **file scope** 

int main()  
{  
   int i;   /* block scope */  
   /* .
      .
      .
   */ 
   return 0;  
}  

这两者有什么区别?

推荐答案

在C99中，没有什么叫做程序作用域".在您的示例中，变量x具有一个文件范围，该文件范围终止于转换单元的末尾.声明为static的变量y和z也具有文件范围，但具有内部链接.

In C99, there's nothing called "program scope". In your example variable x has a file scope which terminates at the end of translation unit. Variables y and z which are declared static also have the file scope but with internal linkage.

C99(6.2.2/3)如果声明了对象的文件作用域标识符 或包含静态存储类说明符的函数， 标识符具有内部链接

C99 (6.2.2/3) If the declaration of a file scope identifier for an object or a function contains the storage class specifier static, the identifier has internal linkage

此外，变量x具有外部链接，这意味着名称x可以被其他翻译单位或整个程序访问.

Also, the variable x has an external linkage which means the name x can is accessible to other translation units or throughout the program.

C99(6.2.2/5)如果对象的标识符声明具有 文件范围，没有存储类说明符，它的链接是外部的.

C99 (6.2.2/5) If the declaration of an identifier for an object has file scope and no storage-class specifier, its linkage is external.

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