'new' operator understanding

Question

need detailed explanation on the 'new' operator in C++. Can somebody explain why the following works:

int *n = new int(10);  // initialize the pointer to integer as '10'
cout << *n;            // o/p -> 10

but this does not work?

int p = new int (10);  // error: invalid conversion from 'int*' to 'int' [-fpermissive]

Why do you expect the second to work? `new` returns a pointer. — NathanOliver, Jul 19 '17 at 16:51
duplicate? https://stackoverflow.com/questions/2726356/the-new-operator-in-c-pointer-question — Twtheo, Jul 19 '17 at 16:52
[The Definitive C++ Book Guide and List](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) — molbdnilo, Jul 19 '17 at 17:01
Possible duplicate of [the "new" operator in c++, pointer question](https://stackoverflow.com/questions/2726356/the-new-operator-in-c-pointer-question) — ytobi, Jul 19 '17 at 17:04

score 0 · Answer 1 · answered Jul 19 '17 at 17:14

new operator used with pointers, not int type so

   int x = 5;
   int *p = &x;
   int *q = new int(4);

and you can use it with classes struct, so on but not pure types I mean just int char .. etc.

this is the declaration of new :

  void* operator new[] (std::size_t size);
  void* operator new[] (std::size_t size, const std::nothrow_t& nothrow_value) noexcept;
  void* operator new[] (std::size_t size, void* ptr) noexcept;

as what you see it's return pointer type void so you cann't in c/c++ write

  int x = p; // error : invalid conversion from 'int*' to 'int'

which is the same as what you did.

score 0 · Answer 2 · answered Jul 19 '17 at 17:37

0

It is quite evident from the error message itself.. error: invalid conversion from 'int*' to 'int'

Since "new" returns a pointer if it is successful. That's why you are getting an error when you are trying to assign it to an int.

answered Jul 19 '17 at 17:37

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'new' operator understanding

2 Answers2