please tell me why memory is not allocated in the line CLNAME* tmp=new CLNAME[this->Capacity_Ram]; the second day I'm looking for a problem, I can not understand what the problem is. The task is to write self-written vectors Code: header:

#pragma once
#include <iostream>
#include <memory.h>

using namespace std;

template <class CLNAME>
class MyVector{
protected:
        CLNAME* Array;
        int Size_Ram = 0;
        int Capacity_Ram = 5;
public:
        MyVector();
        MyVector(const MyVector<CLNAME> &other);
        int Capacity();
        int Size();
        void PushBack(CLNAME item);

};
#include "MyVector.ipp"

ipp:

//Конструкторы
template <class CLNAME>
MyVector<CLNAME>::MyVector() {
    this->Array = new CLNAME[this->Capacity_Ram];
}
template <class CLNAME>
MyVector<CLNAME>::MyVector(const MyVector<CLNAME> &other) {
    this->Capacity_Ram=other.Capacity_Ram;
    this->Size_Ram=other.Size_Ram;
    Array = new CLNAME[other.Capacity_Ram];
    for (int i=0;i<other.Size_Ram;i  ){
        this->Array[i]=other.Array[i];
    }
}


//Методы
template <class CLNAME>
int MyVector<CLNAME>::Capacity(){
    return(this->Capacity_Ram);
};
template <class CLNAME>
int MyVector<CLNAME>::Size(){
    return(this->Size_Ram);
};
template <class CLNAME>
void MyVector<CLNAME>::PushBack(CLNAME item) {
    if (this->Size_Ram==0){
        Array = new CLNAME[this->Capacity_Ram];
        this->Capacity_Ram=Capacity_Ram*2;
    }
    if(Size_Ram==Capacity_Ram){
        this->Capacity_Ram=Capacity_Ram*2;
        CLNAME* tmp=new CLNAME[this->Capacity_Ram];
        for (int i=0;i<Size_Ram;i  ){
            tmp[i]=Array[i];
        }
        delete [] Array;
        Array = tmp;
    }
    Array[Size_Ram]=item;
    Size_Ram =1;
}





//template <class CLNAME>
//MyVector<CLNAME> MyVector<CLNAME>::operator=(MyVector<CLNAME> other) {
    //if (*this == other){
        //return *this
    //}
    //this->Size_Ram=other.Size;
    //this->Capacity_Ram=other.Capacity;
    //this->Array=other.Array;

//};

main:

#include <iostream>
#include "MyVector.h"

int main() {
    MyVector<int> vectors;
    int a=65;
    cout<<vectors.Capacity()<<endl;
    cout<<vectors.Size()<<endl;
    for (int i=0;i<=10;i  ) {
        vectors.PushBack(i);
    }
    cout<<vectors.Size()<<endl;
    cout<<vectors.Capacity()<<endl;
}

CodePudding user response：

In MyVector<CLNAME>::PushBack

if (this->Size_Ram==0){
    Array = new CLNAME[this->Capacity_Ram]; // already done in constructor, leaks.
                                            // sets capacity of 5 
    this->Capacity_Ram=Capacity_Ram*2;      // advertises a capacity of 10, not 5.
}

makes 2 mistakes. 1) storage was already allocated in the constructor so this leaks the constructor's allocation and is unnecessary. 2) Array = new CLNAME[this->Capacity_Ram]; asks for an array of Capacity_Ram elements and then resets the capacity to Capacity_Ram=Capacity_Ram*2; ruining the if(Size_Ram==Capacity_Ram) capacity tests later in the program and allowing out-of-bounds accesses.

Solution: Remove the entire first if and block. The constructor did this already.

Side note: This class needs an assignment operator and a destructor to go along with the copy constructor.