C 是否具有类似于 C++ 的命名空间？

Question

From Programming Language Pragmatics by Michael Scott

Modern versions of C and C++ include a namespace mechanism that provides module-like data hiding

Does C have namespaces similar to C++?

Are the "identifier name spaces" mentioned in C in a Nutshell the "namespaces" mentioned in Scott's book, and similar to namespaces in C++?

Thanks.

Answer 1

No , C does not have a namespace mechanism whereby you can provide “module-like data hiding”.

book quality
I do not know anything about the book you cited, but the word “namespaces” is one of those that gets overloaded to a lot of different meanings, just like “window”. (I question the validity of anything the author says for getting such a major point about one of the world's oldest and most widespread computer languages so brazenly wrong.)

name spaces in C
“Name spaces” in C are a completely different mechanism, working for a completely different purpose. These are the name spaces discussed in “C in a Nutshell”. The words mean something different than C++ namespaces. Since David Rankin bothered to lookup chapter and section referencing the C11 Standard, these are the name spaces used in C:

• label names
• struct/union/enum tags
• struct/union members
• everything else (including enum values)

a quick blurb about scope
Keep in mind that this says nothing about scope , which is a separate mechanism. For example, a global variable and a variable local to a function may have the same name; nevertheless they share the same name space. The difference is that the global's visibility is obscured by the local variable.

value of namespaces in C++
It is still unclear whether namespaces were a very useful extension to C++, and the argument as to its righteousness continues. The C crowd (mostly) agrees that the headache that adding namespaces would involve doesn't justify the ends. I couldn't find anything particularly useful on the interwebs right off the top of my keyboard, except for a couple of bland blurbs about emulating them using structs or (even worse) using macro abuse. If you really want to dig, you could probably find some useful discussions archived on the comp.lang.c newsgroup.

Answer 2

No, C has nothing like C++ namespaces. Most people have to fake what C++ does using a kind of underscore notation at best. This is at least what I do instead of trying to pack things into structs. Your IDE will still help with code assists, you just have to get used to using the underscore instead of a . for everything

C++

MyNamespace::MyObject.myMethodOrVar ...

Ends up looking like this in C

MyNamespace_MyObject_myMethodOrVar

May not be as smooth as C++ or Java, but it works and still helps avoid name collision. It's just a pain in the ass. And yes, this doesn't give you syntactic devices like use . It is what it is I'm afraid.