Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!dlogics!dsa
From: dsa@dlogics.COM (David Angulo)
Newsgroups: comp.lang.c++
Subject: Re: Correction to Re: Default constructor, unexpected call
Summary: buggy code
Message-ID: <615@dlogics.COM>
Date: 7 Aug 90 18:15:59 GMT
References: <26655@pasteur.Berkeley.EDU> <643@atcmpe.atcmp.nl>
Organization: Datalogics Inc., Chicago
Lines: 97

In article <643@atcmpe.atcmp.nl>, leo@atcmp.nl (Leo  Willems) writes:
> My question is simple: why does the following program generate a 
> call to the default constructor from class A for variable 'copd'?
> 
> (If this is not a bug in 2.1 (2.0 as well) try switching the
>  declarations of a and b in class C; then A::A() is not called: if the 
> previous one is NOT a bug then this one is!)
> 
> 
> ============
> 
> #include <stdio.h>
> 
> class A{
> public:
> 	A() { ida = 0; puts("default constructor A()"); }
> 	A(int i) {ida = i; puts("constructor A(int)"); }
> private:
> 	int ida;
> };
> 
> class B{
> public:
> 	B() { idb = 0; puts("default constructor B()"); }
> 	B(B& b) { idb = b.idb; puts("copy constructor B(B&)"); }
> private:
> 	int idb;
> };
> 
> class C{
> public:
> 	C(){ puts("default constructor C()");}
> protected:
> 	A a;	//switch these: bug(?) gone 
> 	B b;    // if not a bug: A::A() gone!!!!
> };
> 
> main()
> {
> 	puts(" first a 'default' constructor:");
> 	C defd;
> 
> 	puts("\n now the copy constructor: ");
> 
> 	C copd(defd);	//suspicious A::A() class here
               ^^^^
       Well, I don't know how this compiled because you don't have
       anything other than a default constructor for class C.  This
       shouldn't have compiled!

> }
> 












I hate this stupid program









This is really stupid












Who wrote this junk?




-- 
David S. Angulo                  (312) 266-3134
Datalogics                       Internet: dsa@dlogics.com
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