Bad allocation exceptions in C++

Question

In a school project of mine, I was requested to create a program without using STL

In the program, I use a lot of

Pointer* = new Something;
if (Pointer == NULL) throw AllocationError();

My questions are about allocation error:

1. is there an automatic exception thrown by new when allocation fails?
2. if so, how can I catch it if I'm not using STL (#include "exception.h")?
3. is NULL testing enough?

Thank You.
I'm using eclipseCDT(C++) with MinGW on Windows 7.

Answer 1

Yes, the new operator will automatically thrown an exception if it cannot allocate the memory.

Unless your compiler disables it somehow, the new operator will never return a NULL pointer.

It throws a bad_alloc exception.

Also there is a nothrow version of new that you can use:

int *p = new(nothrow) int(3);

This version returns a null pointer if the memory cannot be allocated. But also note that this does not guarantee a 100% nothrow, because the constructor of the object can still throw exceptions.

Bit more of information: http://msdn.microsoft.com/en-us/library/stxdwfae(VS.71).aspx

Answer 2

1. is there an autamtic exception thrown by new when allocation fails?
2. if so how can I catch it if I'm not using STL (#include "exception.h)

Yes. See this example. It also demonstrates how to catch the exception!

  try
  {
    int* myarray= new int[10000];
  }
  catch (bad_alloc& ba)
  {
    cerr << "bad_alloc caught: " << ba.what() << endl;
  }

From here : http://www.cplusplus.com/reference/std/new/bad_alloc/

3 . is using the NULL testing enugh?

That is not needed, unless you overload the new operator!

Answer 3

1. Yes: std::bad_alloc

2. In my opinion, that isn't part of the STL any more that operator new is. (You could catch ... but you'll loose the possibility to descriminate with other exceptions).

3. It is unneeded, new will throw an exception and not return NULL.