CODEWITHSUNDEEP
c++c++11recursionsmart-pointers
canatan
canatan

Reputation: 65

how to increment a shared_ptr like you would a normal pointer

I'm trying to print a char array in reverse using c++ smart pointers. I run into two problems. 1 is a runtime error that i'm trying to debug, the other is the fact that every time I have to increment the shared_ptr I have to use the get() method.

I'm pasting both of my functions. One that reverses a string using just pointers. and one that uses shared ptr. 

    int display_string_reversep(char* astring)
{ 
  char* achar = astring;
  if((*achar) != '\0')
    {
      char* x= achar;
      x++;
      display_string_reversep(x);
      cout<<(*achar);
    }
    return 0;
} 
int display_string_reverseup(shared_ptr<char> astring)
{ 
  shared_ptr<char> achar(astring);
  //if((*achar) != '\0')
  if(achar != nullptr)
    {
      if(*(achar.get()+1) != '\0')
    {
      shared_ptr<char> x(achar.get()+1);
      //x++;
      display_string_reverseup(x);
    }
      cout<<(achar);
    }
    return 0;
}

I am new to c++11 and this was just a little exercise that I was putting myself through. The internet has given me no other way to increment a shared pointer so far. Is there ? 

char astring [] = {'F','e','l','l','o','w','\0'};

  display_string_reversep(astring);
  display_string_reverseup(shared_ptr<char>(astring));

Upvotes: 2

Views: 6797

Answers (1)

Jerry101
Jerry101

Reputation: 13367

Do not increment a shared_ptr.

A shared_ptr is a reference-counted pointer to a memory node. Its purpose is to delete the node when the reference count drops to zero. It is not a replacement for a raw pointer.

A shared_ptr can point to an array. In that case, you index into the array. Don't increment the shared_ptr.

If you have a smart pointer to a char array for the purpose of deleting the array when done, you can copy its raw pointer and increment that.

Upvotes: 12

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