A BIg Problem with dynamic memory allocation

Replies

• 

  Raviteja.g

  For dynamic allocation you can use malloc( ) or calloc( ) functions .
  can't you try it.
  and it is one and only way to allocate memory dynamically in C
• 

  pradeep_agrawal

  yamrajbhalla

  i declared a array of pointer *nm[10];
  in class
  
  and i need to input data in it and dynamically allocate memory for this and also i have to show the output

  As you have declared the array of pointers in a class (i.e., using C++), so you can use new/delete operators for this. Consider that the array is array of integer pointers, so code will look like:
  
  

  int *nm[10] = { 0 };              //Initializing array with all poiters set to NULL
  int i = 0;
  
  for(i = 0; i < 10; i++) {
      nm[i] = new int;              //Dynamic memory allocation
      *(nm[i]) =        //Assigning some data
  }
  
  for(i = 0; i < 10; i++) {
      cout<<*(nm[i])<-Pradeep
                                      

• 

  ms_cs

  What error you got?
  For me I have compiled this part.It does not show any error.
  for(i = 0; i < 10; i++) {
  nm = new int; //Dynamic memory allocation
  *(nm) = //Assigning some data
  }
• 

  yamrajbhalla

  thnks for the fast rpyly i did it bt a prob lm occurs always
  after running the programm
  it gives me right output bt after that c++ complier closes and a error occurs
  will u plz hlp me to sort out this problem
• 

  yamrajbhalla

  and by the way thanks for ur precious time to viewing myne problem
  thanks a lotttttt
  bro
• 

  pradeep_agrawal

  yamrajbhalla

  it gives me right output bt after that c++ complier closes and a error occurs

  Could you please update which compiler you are using? Is there any error message displayed when the compiler is closed due to error? If yes, what the message?
  
  Also i had given a code snippet you must have written some code around it. It will be of help in analyzing the issue if you post your code here.
  
  -Pradeep
• 

  yamrajbhalla

  #include
  #include
  #include
  #include
  #include
  #include
  
  
  class bill
  {
  char *item[5];
  int m;
  float itmamt[5];
  public:
  
  void additem(char name[],int i,float prc)
  {
  item=new char[strlen(name) +1];
  strcpy(item,name);
  m=i;
  itmamt=prc;
  }
  void display()
  {
  for(int j=0;j<=m;j++)
  {
  cout< }
  }
  ~bill()
  {delete item;}
  };
  
  void main()
  {float prc;
  clrscr();
  char ch='Y';
  int i=0;
  char *name;
  bill obj;
  do
  {
  cout<<"enter the name of item\n";
  gets(name);
  cout<<"enter the price ";
  cin>>prc;
  
  obj.additem(name,i,prc);
  ++i;
  cout<<"Enter CH";
• 

  pradeep_agrawal

  ~bill()
  {delete item;}
  };

  Above part of the code is creating problem.
  
  This is destructor of the class 'bill' and it is called when the object of this class is destroyed. In your case it will be called when the object 'obj' is destroyed. As the object 'obj' is statically declared in the main function of the class so it gets destroyed when the execution of the main function completes. That's why you are getting error at end of program execution. Now read below for the reason why this particular code segment is causing problem.
  
  When the "delete item;" statement is executed, it tries to delete the memory statically allocated for the array and hence an exception. "delete" should be done for dynamically allocated memory. In your case, "delete" should be called for elements of array. So the destructor should look like
  
  

  ~bill() {
    for(int i = 0; i <= m; i++) {
      delete item[j];
    }
  }

  Let us know if you face the issue after above changes.
  
  -Pradeep
• 

  Raviteja.g

  well pradeep.
  you did a good job.As i don't know much(almost negligible) about C++ i thought pointers are used only in C.
  so i gave my suggestion to use memory allocation functions which allocates memory dynamically
  but now i came to know that pointers are there in C++ too.
  Am i right?
• 

  just2rock

  pradeep_agrawal

  ~bill()
  {delete item;}
  };

  Above part of the code is creating problem.
  
  This is destructor of the class 'bill' and it is called when the object of this class is destroyed. In your case it will be called when the object 'obj' is destroyed. As the object 'obj' is statically declared in the main function of the class so it gets destroyed when the execution of the main function completes. That's why you are getting error at end of program execution. Now read below for the reason why this particular code segment is causing problem.
  
  When the "delete item;" statement is executed, it tries to delete the memory statically allocated for the array and hence an exception. "delete" should be done for dynamically allocated memory. In your case, "delete" should be called for elements of array. So the destructor should look like
  
  

  ~bill() {
    for(int i = 0; i <= m; i++) {
      delete item[j];
    }
  }

  Let us know if you face the issue after above changes.
  
  -Pradeep

  can you pls be more specific about the actual code generating from this.
• 

  pradeep_agrawal

  Raviteja.g

  but now i came to know that pointers are there in C++ too.
  Am i right?

  Yes, C++ have pointers too. And it provides better and more safe ways to handle memory allocations.
  
  

  just2rock

  can you pls be more specific about the actual code generating from this.

  Is there anything specific in the description for which you need more details? I have already mentioned the code snippet of actual code that is causing problem and provided a sample code to fix that.
  
  -Pradeep