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| tokauf@gmail.com: Jul 25 09:40AM -0700 Hi everybody, I have a little class hierachy: |Base| | |Sub| / \ |Sub2| |Sub3| Here's my main-code: 1 #include "Sub2.h" 2 //#include "Sub3.h" 3 4 5 int main () { 6 7 Sub sub("thomas", 53); 8 cout << sub.getMsg() << endl; 9 10 Sub2 sub2 ("Thomas", 53, "Deutschland"); 11 cout << sub2.getMsg() << endl; 12 13 //Sub3 sub3 ("Thomas", 53, "Deutschland", "Male"); 14 //cout << sub3.getMsg() << endl; 15 16 return EXIT_SUCCESS; 17 } This works fine. But when I include Sub3.h and delete the comments from Sub3 sub3 then I get errors: In file included from Sub.h:1:0, from Sub3.h:1, from main.cpp:2: Base.h:3:7: error: redefinition of 'class Base' class Base { ^ In file included from Sub.h:1:0, from Sub2.h:1, from main.cpp:1: Base.h:3:7: error: previous definition of 'class Base' class Base { ^ In file included from Sub3.h:1:0, from main.cpp:2: Sub.h:4:7: error: redefinition of 'class Sub' class Sub : public Base { ^ In file included from Sub2.h:1:0, from main.cpp:1: Sub.h:4:7: error: previous definition of 'class Sub' class Sub : public Base { |
| Paavo Helde <myfirstname@osa.pri.ee>: Jul 25 09:12PM +0300 > from main.cpp:1: > Sub.h:4:7: error: previous definition of 'class Sub' > class Sub : public Base { You need to protect your header files against multiple inclusion. Nowadays in practice it is just OK to put in the start of each header file: #pragma once |
| red floyd <no.spam@its.invalid>: Jul 25 11:12AM -0700 > / \ > |Sub2| |Sub3| > Here's my main-code: [redacted] Search google for "Include Guards". Learn them. Use them. Also, if you are going to post sample code, you need to include your headers. |
| tokauf@gmail.com: Jul 25 12:01PM -0700 > from main.cpp:1: > Sub.h:4:7: error: previous definition of 'class Sub' > class Sub : public Base { Oh my god. I know this rule and I forget it;-). Thank you. |
| Jerry Stuckle <jstucklex@attglobal.net>: Jul 25 03:14PM -0400 On 7/25/2016 2:12 PM, Paavo Helde wrote: > You need to protect your header files against multiple inclusion. > Nowadays in practice it is just OK to put in the start of each header file: > #pragma once Just beware that not all compilers support #pragma once. However, all standards compliant compilers support include guards, i.e. #ifndef __SUB3_H_INCLUDED #define __SUB3_H_INCLUDED .... file goes here 
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