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Full Discussion: About uncopyable class (on book:Effective C++)
Top Forums Programming About uncopyable class (on book:Effective C++) Post 302738345 by vistastar on Saturday 1st of December 2012 05:20:13 AM
Old 12-01-2012
About uncopyable class (on book:Effective C++)
See the following code:
Code:
#include<iostream>
using namespace std;
class Uncopyable
{
protected:
    Uncopyable(){cout<<"hehe\n";}
    ~Uncopyable(){}
private:
    Uncopyable(const Uncopyable &rhs){cout<<"oooops\n";};
    Uncopyable& operator=(const Uncopyable &rhs);
};

class Dog : private Uncopyable
{
    string name;
    int value;
public:

    Dog(const string &s, const int &v):name(s), value(v){}
public:
    //Dog(const Dog &rhs){};             //here is the question!
};

int main()
{
    Dog a("a", 9);
    Dog b(a);
}

If I comment out that line, g++ will complaint "Uncopyable::Uncopyable(const Uncopyable&) is private". I think that mean the default copy ctor of derived class created by g++ called the base class' copy ctor.


If I make available of that line, every thing is ok. It out put
Code:
hehe
hehe

I think this mean the default copy ctor of derived class created by g++ called the base class' default ctor.
Am I right? If yes, why doesn't the default copy ctor derived class, in condition 2, call the base class' copy ctor? Why it behave so inconsistently?

thank you!
Last edited by vistastar; 12-01-2012 at 06:31 AM..
 

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LEARN ABOUT REDHAT

lm

FBB::lm(3bobcat)                                              OFoldStream manipulator                                             FBB::lm(3bobcat)

NAME

       FBB::lm - Manipulator setting left margins of OFoldStream objects

SYNOPSIS

       #include <bobcat/ofoldstream> or
       #include <bobcat/ofoldstreambuf>
       Linking option: -lbobcat

DESCRIPTION

       The lm class implements a manipulator that can be inserted into OFoldStream objects to set the stream's left margin to a requested value.

       Depending  on  the  tab-setting  of  the  OFoldStream  the  inserted value represents the number of blank space characters or the number of
       tab-characters that will be used for the left margin.

       The request will be processed at the next newline character or std::flush or std::endl manipulator that is inserted into the stream.  If  a
       line is still once an lm object and a flush manipulator are inserted into the stream then the new left margin will be effective at the next
       word inserted into that line (cf., the example section below).

       A bad_cast exception is thrown when the manipulator is inserted into an ostream that is not using a OFoldStreambuf buffer.

NAMESPACE

       FBB
       All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB.

INHERITS FROM

       -

CONSTRUCTOR

       o      lm(size_t newValue):
              The standard copy constructor is available.

MEMBER FUNCTIONS

       There are no public or protected member functions in this class.

EXAMPLE

           #include <iostream>
           #include <bobcat/ofoldstream>

           using namespace std;
           using namespace FBB;

           int main()
           {
               OFoldStream out(cout, 0, 80);
               out << "hello world (left margin is 0)" << lm(4) << "
"
                      "this uses a 4 character wide left margin
" <<
                      lm(0) << flush << "at column 0 again
";
               return 0;
           }

FILES

       bobcat/lm - defines the class interface

SEE ALSO

       bobcat(7), manipulators(3bobcat), mlm(3bobcat), ofoldstream(3bobcat)

BUGS

       None Reported.

DISTRIBUTION FILES

       o      bobcat_3.01.00-x.dsc: detached signature;

       o      bobcat_3.01.00-x.tar.gz: source archive;

       o      bobcat_3.01.00-x_i386.changes: change log;

       o      libbobcat1_3.01.00-x_*.deb: debian package holding the libraries;

       o      libbobcat1-dev_3.01.00-x_*.deb: debian package holding the libraries, headers and manual pages;

       o      http://sourceforge.net/projects/bobcat: public archive location;

BOBCAT

       Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.

COPYRIGHT

       This is free software, distributed under the terms of the GNU General Public License (GPL).

AUTHOR

       Frank B. Brokken (f.b.brokken@rug.nl).

libbobcat1-dev_3.01.00-x.tar.gz                                      2005-2012                                                    FBB::lm(3bobcat)
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