[.net]What exception is thrown in .NET when a single object is bigger than 2 GB on a 64-bit OS?

Question

I'm sure I saw this happening to me once. In a 64-bit OS with 8 GB of RAM, I would still get an Exception when an array will be ca. 2 GB. What's the exception name?

Please, don't tell me that my program is bad because I shouldn't be doing that. Believe me, it was required.

EDIT: The program was running as a 64-bit process.

Answer 1

OutOfMemoryException perhaps? Just because your machine has 8GB of memory doesn't mean that your application has access to all of it.

Without knowing any more than what you have posted, I would assume that your application is running in a 32-bit process (even though you are on a 64-bit processor) and as such is limited to the 2GB virtual address space of that 32-bit process. This is all just speculation of course, there are many reasons why you could see an OutOfMemoryException and without more details it is impossible to say why.

Answer 2

You should just get a System.OutOfMemoryException

Look at this page for a discussion about it. (Sorry for the google cache result, the dotnet247.com site appears to be down at the time of this answer)

Answer 3

The following throws OutOfMemoryException on my Windows Server 2008 64 bit with 8Gb RAM:

var a = new int[int.MaxValue];

Answer 4

I checked (Vista Ultimate 64bit with 4GB physical memory), the code:

byte[] x = new byte[2147483648];

throws an OverflowException (because 2147483648 doesn't fit into a signed int)

byte[] x = new byte[2147483647];

throws an OutOfMemoryException

byte[] x = new byte[2147483591];

successfully allocates the array, that is the maximum size that works on my machine.

according to this post http://blogs.msdn.com/joshwil/archive/2005/08/10/450202.aspx it's was a design choice to artificially limit managed object size to 2GB.

You can allocate unmanaged memory using P/Invoke and access it with unsafe code and pointers if you must.