good day! I study with ++ according to the book Stephen Prata wrote a class

#ifndef COW_H_ #define COW_H_ class Cow { private: char name[20]; char * hobby; double weight; public: Cow(); Cow(const char *nm, const char *ho, double wt); Cow(const Cow & c); ~Cow(); Cow & operator=(const Cow & c); void ShowCow() const; }; #endif

class methods are as follows:

 #include "cow.h" #include <iostream> #include <cstring> Cow::Cow() { strcpy(name, "NONE"); hobby = new char[5]; strcpy(hobby, "NONE"); weight = 0.0; } Cow::Cow(const char *nm, const char *ho, double wt) { if(nm == nullptr) { strcpy(name, "NONE"); } else { strncpy(name, nm, 19); name[19] = '\0'; } if(ho == nullptr) { hobby = new char[5]; strcpy(hobby, "NONE"); } else { int len = strlen(ho); hobby = new char[len+1]; strcpy(hobby, ho); } weight = wt; } Cow::Cow(const Cow & c) { strcpy(name, c.name); delete [] hobby; hobby = new char[strlen(c.hobby) + 1]; strcpy(hobby, c.hobby); weight = c.weight; } void Cow::ShowCow() const { std::cout << "Name: " << name << std::endl << "Hobby: " << hobby << std::endl << "Weight: " << weight << std::endl; } Cow::~Cow() { delete [] hobby; } Cow & Cow::operator=(const Cow & c) { if(this == &c) { return *this; } strcpy(name, c.name); delete [] hobby; hobby = new char[strlen(c.hobby) + 1]; strcpy(hobby, c.hobby); weight = c.weight; return *this; }

a program is written to it:

 #include <iostream> #include "cow.h" int main() { Cow one; Cow two("COwjsldnfsdn,sdnf,sndfsdmds","Music", 120.0); std::cout << "one: " << std::endl; one.ShowCow(); std::cout << "two:" << std::endl; two.ShowCow(); std::cout << "Three" << std::endl; Cow three = two; three.ShowCow(); three = two; three.ShowCow(); Cow four(one); std::cout << "Four = one:" << std::endl; four.ShowCow(); four = two; std::cout << "Four = two:" << std::endl; four.ShowCow(); return 0; }

falls in the next line:

Cow three = two;

one: Name: NONE Hobby: NONE Weight: 0 two: Name: COwjsldnfsdn, sdnf, s Hobby: Music Weight: 120 Three Segmentation Error (memory dump made)

What I nakosyachil?

    1 answer 1

    In the constructor

     Cow::Cow(const Cow & c) { strcpy(name, c.name); delete [] hobby; hobby = new char[strlen(c.hobby) + 1]; strcpy(hobby, c.hobby); weight = c.weight; }

    Here is this line

     delete [] hobby;

    need not. You just create an object, the memory has not yet been allocated, you have nothing to delete! Remove this line.

    (But in the assignment operator you do everything right, there it is needed, there you assign it to an already existing object, and hobby is a pointer to the already allocated memory ...)

    • thanks, it worked! - Ivan
    • No doubt :) Well, if everything is OK, close the question, marking the answer as accepted ... - Harry
    • in 7 minutes, there was no time before - Ivan