VC, Static members in Templates

Static members in Templates

Author	Message
Richard Hafne #1 / 4	Static members in Templates Hi! I got the following: -----8<-----8<-----8<-----8<-----8<----- template <class T> class Test { public: static T Value; Quote: }; int main() { Test<int>::Value=2; Test<int> Blah; Blah.Value=1; return 0; Quote: } -----8<-----8<-----8<-----8<-----8<----- At compiling time, I get an C4101 'Blah' : unreferenced local variable At linktime I get an LNK2001: unresolved external symbol "public: static int Test<int>::Value" I look up in the MSDN and found the Liner error bug acknowledged in Q179273. But I am not satisfied with the recommended "resolution". I need en explicit global variable for every template-instance and I dont know a workaround except of manuall creation. Could someone help me? Tanks in advance! In this sense - Richie
Sat, 21 Dec 2002 03:00:00 GMT

Joe Delekt #2 / 4	Static members in Templates Greets, One will want to move the static initialization outside of the main and be sure to specify the type for the static variable as well. The following should yield the desired result: Quote: > Hi! > I got the following: > -----8<-----8<-----8<-----8<-----8<----- > template <class T> > class Test > { > public: > static T Value; > }; > int main() > { > Test<int>::Value=2; > Test<int> Blah; > Blah.Value=1; > return 0; > } > -----8<-----8<-----8<-----8<-----8<----- > At compiling time, I get an C4101 'Blah' : unreferenced local variable > At linktime I get an LNK2001: unresolved external symbol "public: static int > Test<int>::Value" > I look up in the MSDN and found the Liner error bug acknowledged in Q179273. > But I am not satisfied with the recommended "resolution". I need en explicit > global variable for every template-instance and I dont know a workaround > except of manuall creation. > Could someone help me? > Tanks in advance! > In this sense - Richie
Sat, 21 Dec 2002 03:00:00 GMT

Joe Delekt #3 / 4	Static members in Templates Greets, One will want to initialize the static member outside of the template and also use the appropriate type when doing such. The following should yield the desired result: ----------------------- #include <iostream> template <class T> class Test { public: Test() {} /* do away with unreferenced local variable warning */ public: static T Value; Quote: }; int Test<int>::Value=1; char Test<char>::Value='a'; int main() { using std::cout; using std::endl; cout << Test<int>::Value << endl; cout << Test<char>::Value << endl; Test<int> oIntObject; Test<char> oCharObject; cout << oIntObject.Value << endl; cout << oCharObject.Value << endl; oIntObject.Value=2; oCharObject.Value='b'; cout << oIntObject.Value << endl; cout << oCharObject.Value << endl; return(0); Quote: } --------------------------------- Regards, Joe Quote: > Hi! > I got the following: > -----8<-----8<-----8<-----8<-----8<----- > template <class T> > class Test > { > public: > static T Value; > }; > int main() > { > Test<int>::Value=2; > Test<int> Blah; > Blah.Value=1; > return 0; > } > -----8<-----8<-----8<-----8<-----8<----- > At compiling time, I get an C4101 'Blah' : unreferenced local variable > At linktime I get an LNK2001: unresolved external symbol "public: static int > Test<int>::Value" > I look up in the MSDN and found the Liner error bug acknowledged in Q179273. > But I am not satisfied with the recommended "resolution". I need en explicit > global variable for every template-instance and I dont know a workaround > except of manuall creation. > Could someone help me? > Tanks in advance! > In this sense - Richie
Sat, 21 Dec 2002 03:00:00 GMT

Todd Gree #4 / 4	Static members in Templates Quote: > template <class T> > class Test > { > public: > static T Value; > }; template<class T> T Test<T>::Value; Quote: > int main() > { > Test<int>::Value=2; > Test<int> Blah; > Blah.Value=1; > return 0; > } > -----8<-----8<-----8<-----8<-----8<----- > At compiling time, I get an C4101 'Blah' : unreferenced local variable > At linktime I get an LNK2001: unresolved external symbol "public: static int > Test<int>::Value" > I look up in the MSDN and found the Liner error bug acknowledged in Q179273. > But I am not satisfied with the recommended "resolution". I need en explicit > global variable for every template-instance and I dont know a workaround > except of manuall creation. > Could someone help me? I just compiled, linked, and ran your program with the addition shown above, which is not, I believe, a workaround, but rather the correct way to do it. I still got the unreferenced local variable warning, which makes sense, because Blah really isn't being referenced. The knowledge base article you cite is just pointing out, if you'd wanted to initialize Value with some value other than 0, saying template<class T> T Test<T>::Value(42); would not work (this is a bug), but that template<class T> T Test<T>::Value = 42; does work. I'm using VC6 sp3. I wouldn't be at all surprised if earlier versions didn't grok this. --
Sun, 19 Jan 2003 03:00:00 GMT

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