我们可以在没有 static 关键字的情况下声明具有内部链接的文件范围标识符吗？

Question

C 标准的第 6.11.2 节说明了在 future 版本中可能会被弃用的功能之一:

Declaring an identifier with internal linkage at file scope without the static storage-class specifier is an obsolescent feature.

在没有静态存储类说明符的情况下，如何声明文件范围标识符以具有内部链接？

Answer 1

在 C++ 标准中有一个针对此问题的具体示例。
在 [dcl.stc] 中:

static int b; // b has internal linkage
extern int b; // b still has internal linkage

因此，在第二行中，b 被声明为具有内部链接的文件范围标识符，没有关键字 static。
这个例子也适用于 C，如 C11:6.2.2 所说:

For an identifier declared with the storage-class specifier extern in a scope in which a prior declaration of that identifier is visible, if the prior declaration specifies internal or external linkage, the linkage of the identifier at the later declaration is the same as the linkage specified at the prior declaration. If no prior declaration is visible, or if the prior declaration specifies no linkage, then the identifier has external linkage.

see this question for more detail