C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Terminology - global          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message bob Guest Posted: Thu Feb 24, 2005 4:26 pm    Post subject: Terminology - global Stroustrup 3rd edition, 4.9.4, 2nd paragraph: "A name is called global if it is declared outside any function, class (Chapter 10), or namespace. The scope of a global name extends from the point of declaration to the end of the file in which its declaration occurs." Is x in the following global? // Start of a file static const int x = 0; class MyClass { //etc. I know such usage is deprecated (ref: B.2.3 in the above). Back to top Victor Bazarov Guest Posted: Thu Feb 24, 2005 4:40 pm    Post subject: Re: Terminology - global bob wrote: Quote: Stroustrup 3rd edition, 4.9.4, 2nd paragraph: "A name is called global if it is declared outside any function, class (Chapter 10), or namespace. The scope of a global name extends from the point of declaration to the end of the file in which its declaration occurs." Is x in the following global? // Start of a file static const int x = 0; class MyClass { //etc. I know such usage is deprecated (ref: B.2.3 in the above). Yes, it is global in the sense used in the quote you presented. I am more used to a small correction (or addition) to that definition. A name defined outside of any function, class, or namespace, _and_ has external linkage. That makes it really global, i.e. visible from other translation units. However, the quote you gave is in the section that talks about scope, about name hiding, and about the ways to access global names using the scope resolution operator (:, so linkage is not involved. V Back to top bob Guest Posted: Thu Feb 24, 2005 5:36 pm    Post subject: Re: Terminology - global Thanks Victor. This was provoked by a code review at my place of employment. The code snippet was: // Local static const int x = 0; class { etc. I objected to the "Local" comment (and the fact that such usage is deprecated). Believe it or not, this lead to about 5 email exchanges. The problem is semantics as you pointed out: There is "global" and "really global". The term "global" (ala Stroustrup) is overloaded in the sense that it can refer to either meaning. I think many/most programmers use the "really global" interpretation and thus the "Local" comment in the code snippet. Bob. Back to top Alf P. Steinbach Guest Posted: Thu Feb 24, 2005 5:45 pm    Post subject: Re: Terminology - global * bob: Quote: Thanks Victor. This was provoked by a code review at my place of employment. The code snippet was: // Local static const int x = 0; class { etc. I objected to the "Local" comment (and the fact that such usage is deprecated). Believe it or not, this lead to about 5 email exchanges. The problem is semantics as you pointed out: There is "global" and "really global". The term "global" (ala Stroustrup) is overloaded in the sense that it can refer to either meaning. I think many/most programmers use the "really global" interpretation and thus the "Local" comment in the code snippet. One alternative is to use a word such as "private". Of course that's overloaded too. Any way, the comment above is like this one: a = b + c; // Compute the sum of b and c, and assign that to a. If someone doesn't know what "static" means, then that someone has no business maintaining the code. So I agree, the comment was a bad 'un (I also agree with Victor about the usual interpretation of "global", and there are more). -- A: Because it messes up the order in which people normally read text. Q: Why is it such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? Back to top Daniel Lidström Guest Posted: Thu Feb 24, 2005 5:47 pm    Post subject: Re: Terminology - global On Thu, 24 Feb 2005 09:36:45 -0800, bob wrote: Quote: There is "global" and "really global". The term "global" (ala Stroustrup) is overloaded in the sense that it can refer to either meaning. I think many/most programmers use the "really global" interpretation and thus the "Local" comment in the code snippet. How can the variable be made "really" global? -- Daniel Back to top Victor Bazarov Guest Posted: Thu Feb 24, 2005 6:12 pm    Post subject: Re: Terminology - global Daniel Lidström wrote: Quote: On Thu, 24 Feb 2005 09:36:45 -0800, bob wrote: There is "global" and "really global". The term "global" (ala Stroustrup) is overloaded in the sense that it can refer to either meaning. I think many/most programmers use the "really global" interpretation and thus the "Local" comment in the code snippet. How can the variable be made "really" global? If you look at the original post and my reply, the variable in question was declared 'static' which meant it had internal linkage. It is also const, which gives it even more internal linkage (if that's possible). To make it "really global" in *my* meaning of "global", it had to be declared 'extern', which along with the initialiser would give it external linkage while defining it in this module: extern const int x = 0; Now, 'x' is visible from other translation units. If in another module you declare it extern const int x; then the symbol will be resolved during linking. V Back to top Howard Guest Posted: Thu Feb 24, 2005 8:41 pm    Post subject: Re: Terminology - global "Victor Bazarov" <v.Abazarov (AT) comAcast (DOT) net> wrote Quote: Daniel Lidstrvm wrote: On Thu, 24 Feb 2005 09:36:45 -0800, bob wrote: There is "global" and "really global". The term "global" (ala Stroustrup) is overloaded in the sense that it can refer to either meaning. I think many/most programmers use the "really global" interpretation and thus the "Local" comment in the code snippet. How can the variable be made "really" global? If you look at the original post and my reply, the variable in question was declared 'static' which meant it had internal linkage. It is also const, which gives it even more internal linkage (if that's possible). To make it "really global" in *my* meaning of "global", it had to be declared 'extern', which along with the initialiser would give it external linkage while defining it in this module: extern const int x = 0; Now, 'x' is visible from other translation units. If in another module you declare it extern const int x; then the symbol will be resolved during linking. V Why do you need the "extern" where it's defined... because it's a const? For variables that are not const, the extern specifier is only needed in the "other" modules, correct? -Howard Back to top Victor Bazarov Guest Posted: Thu Feb 24, 2005 8:47 pm    Post subject: Re: Terminology - global Howard wrote: Quote: [..] Why do you need the "extern" where it's defined... because it's a const? For variables that are not const, the extern specifier is only needed in the "other" modules, correct? Yes, both correct. Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.