malloc vs new

[thescratchy]

Hello

I have an array of pointers. I want to take a pointer from this array and return this.
If I use new I get a segmentation fault. But when I use malloc it is ok.

SegFault
ClassEx* Example::doSomething()
{
          ClassEx *array = new ClassEx[5];
          fill in

          return &array[2];
}

Ok
ClassEx* Example::doSomething()
{
          ClassEx *array = (ClassEx*) malloc(sizeof(ClassEx) * 5);
          fill in

          return &array[2];
}

Can someone explain me why malloc works here and new doesn't.

Also how do I return a pointer to an element in an array using new?

Thank you

[anon]

The difference is that malloc doesn't construct any objects. So if there's something wrong with the constructor...

Or there is other undefined behavior in the program and this is just how it manifests.

[iMalc]

Show the code for the constructor.

[grumpy]

Show the code for the constructor.

.... of ClassEx.

If the problem is not in that constructor, then the problem is somewhere else in your code. That may seem like stating the obvious, but one of the joys of program crashes is that they are not always immediate. The cause of the problem is typically in code executed before the crash occurs. Unfortunately a trap for new players - and quite a few experienced players - is insisting on only looking at the code where the crash occurs.

[iMalc]

Actually I'm thinking now that there are actually several other things that are suspect here. For one, if it's returning the address of array element two, then how is the memory freed later?
The question is not

how do I return a pointer to an element in an array using new?

but, why would you want to return a pointer to an element within an array that is dynamically allocated within that function?

Secondly, whatever code is where you wrote "fill in" could also well be the problem.

[thescratchy]

Thank you for the responses.
The problem was indeed in the constructor.