Re: why is int a[0] not allowed, but int* a = new int[0] is?

haijin.biz@gmail.com wrote:
::::: b[0]=123; // why we can play with b[0] and b[1] as if we had
::::: allocated space for 2 ints?
::::: b[1]=456;
::::: /// b[2]=789; // error
:::
::: They are all errors!
:::
::: You are not allowed to "play" with anything outside the size of the
::: object. None in this case.
:::
:::::
::::: cout<<b[0]<<endl;
::::: cout<<b[1]<<endl;
:::
::: Can't do that either, there are no elements in b.
::
::: Bo Persson
::
::
:: Thanks Bo. I understand that it may be the problem of a particular
:: c++ complier for allowing
::
:: b[0] = 1;
:: b[1] = 2;
::
:: when all we did before that is int* b = new int[0].
::
:: I am using VS 2005 and two assignments are okay, although I think it
:: must crash the program.

It doesn't have to. Assigning outside the size of an array is "undefined
behaviour" in C++ speak. That means that it might crash, or seems to work,
or something else. The language standard doesn't say what must happen, just
that you shouldn't do it.

Bo Persson