1.15.2. Operators new and delete

1.15.2. Operators `new` and `delete`
	1.15. Pointers and Memory Access

1.15.2. Operators `new` and `delete`

[ fromfile: pointers.xml id: newdelete ]

C++ has a mechanism that permits storage to be allocated dynamically at runtime.

The new operator allocates storage from the heap (also known as dynamic storage) and returns a pointer to the newly allocated object.
If for some reason it is not possible for the memory to be allocated, an exception is thrown.^[12]

The delete operator releases dynamically allocated memory and returns it to the heap.
delete should be applied only to pointers returned by new, or to null pointers.
Heap memory that is no longer needed should be released for reuse.
Failure to do so can result in crippling memory leaks.

In general, the code that calls new should document, or be physically located near, the code that frees the memory.

Dereferencing a null, deleted, or uninitialized pointer causes a runtime error, usually a segmentation fault or, in Windows, a general protection fault (GPF).
It is the responsibility of the programmer to make sure that this cannot happen.

The syntax of the new and delete operators is demonstrated in the code fragment shown in Example 1.28.

Example 1.28. src/pointers/newdelete/ndsyntax.cpp

#include <iostream>
using namespace std;

int main() {
 int* ip = 0;               
 delete ip;                 
 if(ip) cout << "non-null" << endl;
 else cout << "null" << endl;
 ip = new int;              
 int* jp = new int(13);     
 //[...]      
 delete ip;                 
 delete jp;
}

	null pointer
	has no effect at all - ip is still null.
	allocate space for an int
	allocate and initialize
	Without this, we have a memory leak.

^[12]We discuss this situation in an article on our Website.


1.15.1. The Unary Operators & and *		1.15.3. Exercises: Pointers and Memory Access