Unable to allocate very big arrays

[MichalStrehovsky]

We have System.Runtime tests that test allocating the maximally supported arrays. We throw an OutOfMemoryException for them. Likely because this code:

runtimelab/src/coreclr/nativeaot/Runtime/gcrhenv.cpp

Lines 239 to 263 in 8fac0a8

	// higher limit for array of bytes (or one byte structs) for backward compatibility.
	// Keep in sync with Array.MaxArrayLength in BCL.
	if (cbSize > MaxByteArrayLength /* note: comparing allocation size with element count */)
	{
	// Ensure the above if check covers the minimal interesting size
	static_assert(MaxByteArrayLength < (uint64_t)MaxArrayLength * 2, "");
	if (pEEType->IsArray())
	{
	if (pEEType->get_ComponentSize() != 1)
	{
	size_t elementCount = (cbSize - pEEType->get_BaseSize()) / pEEType->get_ComponentSize();
	if (elementCount > MaxArrayLength)
	return NULL;
	}
	else
	{
	size_t elementCount = cbSize - pEEType->get_BaseSize();
	if (elementCount > MaxByteArrayLength)
	return NULL;
	}
	}
	}
	if (cbSize >= RH_LARGE_OBJECT_SIZE)

Is checking the allocation size instead of element count. Allocation size has already been aligned up.

[jkotas]

Fixed in #971

[MichalStrehovsky]

The test is still failing. I think the problem is still that we are comparing the element count to the limit only after we don't have the actual element count anymore and we need to recompute it from the allocation size. The allocation size has already been aligned up to what the GC needs so it looks like we want more elements than what was requested.

[jkotas]

The test is passing for me now.