.NET OutOfMemoryException

Question

Why does this:

class OutOfMemoryTest02
{
    static void Main()
    {
        string value = new string('a', int.MaxValue);
    }
}

Throw the exception; but this wont:

class OutOfMemoryTest
{
    private static void Main()
    {
        Int64 i = 0;
        ArrayList l = new ArrayList();
        while (true)
        {
            l.Add(new String('c', 1024));

            i++;
        }
    }
}

Whats the difference?

Answer 1

Have you looked up int.MaxValue in the docs? it's the equivalent of 2GB, which is probably more RAM than you have available for a contiguous block of 'a' characters - that is what you are asking for here.

http://msdn.microsoft.com/en-us/library/system.int32.maxvalue.aspx

Your infinite loop will eventually cause the same exception (or a different one indirectly related to overuse of RAM), but it will take a while. Try increasing 1024 to 10 * 1024 * 1024 to reproduce the symptom faster in the loop case.

When I run with this larger string size, I get the exception in under 10 seconds after 68 loops (checking i).