C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  static extern?          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Gernot Frisch Guest Posted: Mon Jun 28, 2004 9:21 am    Post subject: static extern? Problem: A.cpp: ------ static FOO* gFoo=NULL; A.h extern FOO* gFoo; gives: L2001 - unresolved external: "symbol struct FOO* gFoo" if A.h looks like: extern static FOO* gFoo; it gives: C2159: more than one storage class specified. <blink, blink> How would I do this now? I have a prefedined macro that makes a "static FOO*". And I want to tell all my other .cpp files that it exists in stdafx.h. Thank you, -- -Gernot int main(int argc, char** argv) {printf ("%silto%c%cf%cgl%ssic%ccom%c", "ma", 58, 'g', 64, "ba", 46, 10);} ________________________________________ Looking for a good game? Do it yourself! GLBasic - you can do www.GLBasic.com Back to top Vince Yuan Guest Posted: Mon Jun 28, 2004 9:53 am    Post subject: Re: static extern? Try this: A.h static FOO* gFoo; A.cpp: extern static FOO* gFoo=NULL; Vince "Gernot Frisch" <Me (AT) Privacy (DOT) net> wrote Quote: Problem: A.cpp: ------ static FOO* gFoo=NULL; A.h extern FOO* gFoo; gives: L2001 - unresolved external: "symbol struct FOO* gFoo" if A.h looks like: extern static FOO* gFoo; it gives: C2159: more than one storage class specified. blink, blink How would I do this now? I have a prefedined macro that makes a "static FOO*". And I want to tell all my other .cpp files that it exists in stdafx.h. Thank you, -- -Gernot int main(int argc, char** argv) {printf ("%silto%c%cf%cgl%ssic%ccom%c", "ma", 58, 'g', 64, "ba", 46, 10);} ________________________________________ Looking for a good game? Do it yourself! GLBasic - you can do www.GLBasic.com Back to top Mark Warren Guest Posted: Mon Jun 28, 2004 10:15 am    Post subject: Re: static extern? Gernot Frisch wrote: Quote: Problem: A.cpp: ------ static FOO* gFoo=NULL; A.h extern FOO* gFoo; gives: L2001 - unresolved external: "symbol struct FOO* gFoo" if A.h looks like: extern static FOO* gFoo; it gives: C2159: more than one storage class specified. Yes, the variable gFoo cannot be static and extern at the same time. Quote: blink, blink How would I do this now? I have a prefedined macro that makes a "static FOO*". And I want to tell all my other .cpp files that it exists in stdafx.h. Thank you, Solution: A.cpp: ------ FOO* gFoo=NULL; // Note no static A.h ---- extern FOO* gFoo; HTH Mark Back to top Gernot Frisch Guest Posted: Mon Jun 28, 2004 11:43 am    Post subject: Re: static extern? Quote: Solution: A.cpp: ------ FOO* gFoo=NULL; // Note no static A.h ---- extern FOO* gFoo; I rewrote the code so I can do this now. But I don't understand it. Why can't I tell another .cpp file that there is an static variable somewhere else? -Gernot Back to top Sharad Kala Guest Posted: Mon Jun 28, 2004 11:48 am    Post subject: Re: static extern? "Gernot Frisch" <Me (AT) Privacy (DOT) net> wrote Quote: Solution: I rewrote the code so I can do this now. But I don't understand it. Why can't I tell another .cpp file that there is an static variable somewhere else? Because static variables having namespace scope have internal linkage i.e. the entity it denotes can be referred to by names from other scopes in the same translation unit only. Back to top Rolf Magnus Guest Posted: Mon Jun 28, 2004 12:33 pm    Post subject: Re: static extern? Gernot Frisch wrote: Quote: Problem: A.cpp: ------ static FOO* gFoo=NULL; A.h extern FOO* gFoo; gives: L2001 - unresolved external: "symbol struct FOO* gFoo" Well, static means internal linkage, extern means external linkage. You have to choose one. If the variable is static, it doesn't make much sense to declare it as extern in the header. Quote: if A.h looks like: extern static FOO* gFoo; it gives: C2159: more than one storage class specified. blink, blink How would I do this now? I have a prefedined macro that makes a "static FOO*". And I want to tell all my other .cpp files that it exists in stdafx.h. Why? It's static, so it doesn't exist outside of the .cpp file where it's defined. Back to top Gernot Frisch Guest Posted: Mon Jun 28, 2004 1:02 pm    Post subject: Re: static extern? Quote: Why? It's static, so it doesn't exist outside of the .cpp file where it's defined. Because: That is exactly what I didn't know. Thank you, Gernot Back to top Andrey Tarasevich Guest Posted: Mon Jun 28, 2004 6:39 pm    Post subject: Re: static extern? Gernot Frisch wrote: Quote: ... Why can't I tell another .cpp file that there is an static variable somewhere else? Because that what this particular use of 'static' is intended to do in the first place! It is intended to make the variable "invisible" from other translation units. If you want to be able to link to that variable from other translation units - give it external linkage. -- Best regards, Andrey Tarasevich Back to top Jack Klein Guest Posted: Tue Jun 29, 2004 2:32 am    Post subject: Re: static extern? On Mon, 28 Jun 2004 17:53:22 +0800, "Vince Yuan" <shinebean (AT) citiz (DOT) net> wrote in comp.lang.c++: First, don't top post. Quote: Try this: A.h static FOO* gFoo; A.cpp: extern static FOO* gFoo=NULL; Vince Second, this is complete nonsense. -- Jack Klein Home: http://JK-Technology.Com FAQs for comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html comp.lang.c++ http://www.parashift.com/c++-faq-lite/ alt.comp.lang.learn.c-c++ http://www.contrib.andrew.cmu.edu/~ajo/docs/FAQ-acllc.html Back to top Howard Guest Posted: Tue Jun 29, 2004 10:29 pm    Post subject: Re: static extern? "Rolf Magnus" <ramagnus (AT) t-online (DOT) de> wrote Quote: Gernot Frisch wrote: Problem: A.cpp: ------ static FOO* gFoo=NULL; A.h extern FOO* gFoo; gives: L2001 - unresolved external: "symbol struct FOO* gFoo" Well, static means internal linkage, extern means external linkage. You have to choose one. If the variable is static, it doesn't make much sense to declare it as extern in the header. <rant> You know, I can't for the life of me figure out why "static" was used to mean internal linkage in this case. I'd think "intern" or something similar would be much more logical, and simply eliminate the use of "static" for non-member functions and variables. I know this is not the forum for asking "why", but it really bugs me to have a keyword that has no apparent relation to its use. One would think that "static" should have the same (or at least similar) meaning in this context as it does in member functions and variables. And since it makes no sense to try to apply the same meaning in this case as in the member (or local variable) case, it really just shouldn't exist at all here. "But that's just my opinion...I could be wrong." </rant> -Howard Back to top Rolf Magnus Guest Posted: Wed Jun 30, 2004 10:20 pm    Post subject: Re: static extern? Howard wrote: Quote: Well, static means internal linkage, extern means external linkage. You have to choose one. If the variable is static, it doesn't make much sense to declare it as extern in the header. rant You know, I can't for the life of me figure out why "static" was used to mean internal linkage in this case. I'd think "intern" or something similar would be much more logical, and simply eliminate the use of "static" for non-member functions and variables. I think they didn't want to introduce a new keyword. Also, they wanted to remain compatible to C, which alread had defined it this way. And actionally the meaning that static has within a class definition is the youngest one. Quote: I know this is not the forum for asking "why", but it really bugs me to have a keyword that has no apparent relation to its use. I had more problems with the syntax they chose for pure virtual functions. "Initializing" a function declaration with 0 looks very odd to me. But again, I suspect they didn't want to add a new keyword "pure". Quote: One would think that "static" should have the same (or at least similar) meaning in this context as it does in member functions and variables. It depends on how you look at it. If you look at it the right way, static has more or less always the same meaning. Within a class, static means that the function or variable is only there once, for the class, not for each instance of it. Same for a local static variable, if you count calling a function as "instantiating" it. Well, and a static variable/function on namespace scope is there for this one translation unit. It always has a meaning similar to "there is only one". 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.