C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  usage of PRIVATE members in derived class without errors?          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message mario semo Guest Posted: Fri Dec 08, 2006 6:52 am    Post subject: usage of PRIVATE members in derived class without errors? Hello, in the following sample the "typedef ClassName Inherited" is privat in all classes except the top level class, where it is not defined, BUT USED! so the MainClass uses "Inherited::" which is a private typedef from baseclasses. The code compiles fine with IBM VACPP 3.5 (WinNT compiler) MSVC++ 6.x GCC 2.95.2-6 (have not tried other compiles). Why can the derived class access the privat typedef from the baseclasses? #include <stdio.h> class Base { //-------------------------------------------------------------------------- private: //-------------------------------------------------------------------------- typedef Base Inherited; //-------------------------------------------------------------------------- public: //-------------------------------------------------------------------------- Base() {} virtual ~Base() {} virtual void foo() {printf("base::foo\n");} }; class Derived : public Base { //-------------------------------------------------------------------------- private: //-------------------------------------------------------------------------- typedef Base Inherited; //-------------------------------------------------------------------------- public: //-------------------------------------------------------------------------- Derived(){} virtual ~Derived(){} virtual void foo() {printf("Derived::foo\n");} }; class MainC : public Derived { //-------------------------------------------------------------------------- public: //-------------------------------------------------------------------------- MainC() {} virtual ~MainC(){} virtual void foo() { printf("---1---\n"); Inherited::foo(); printf("---2---\n"); } }; int main (int argc,char *argv[]) { MainC aM; aM.foo(); return 0; } -- mit freundlichen Grüßen/best regards mario semo [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Daniel Krügler Guest Posted: Sat Dec 09, 2006 2:59 am    Post subject: Re: usage of PRIVATE members in derived class without errors mario semo schrieb: Quote: in the following sample the "typedef ClassName Inherited" is privat in all classes except the top level class, where it is not defined, BUT USED! so the MainClass uses "Inherited::" which is a private typedef from baseclasses. The code compiles fine with IBM VACPP 3.5 (WinNT compiler) MSVC++ 6.x GCC 2.95.2-6 (have not tried other compiles). Why can the derived class access the privat typedef from the baseclasses? Obviously these compilers all behave non-compliant in this usecase. The typedef should not be accessible in your described scenario. E.g. Comeau online (http://www.comeaucomputing.com/tryitout/) does not accept your code. Greetings from Bremen, Daniel Krügler -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top James Kanze Guest Posted: Sat Dec 09, 2006 3:00 am    Post subject: Re: usage of PRIVATE members in derived class without errors mario semo wrote: Quote: in the following sample the "typedef ClassName Inherited" is privat in all classes except the top level class, where it is not defined, BUT USED! so the MainClass uses "Inherited::" which is a private typedef from baseclasses. The code compiles fine with IBM VACPP 3.5 (WinNT compiler) MSVC++ 6.x GCC 2.95.2-6 (have not tried other compiles). I don't know about the IBM compiler, but the other two are very old. G++, for example, was very careless in its enforcing of private for a long time. Your code is illegal, and doesn't compile with more recent versions of g++. Nor with Sun CC 5.8, the other recent compiler I have immediate access to. -- James Kanze (GABI Software) email:james.kanze (AT) gmail (DOT) com Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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