RFR: 8237521: Memory Access API fixes for 32-bit

[David Holmes]

On 24/01/2020 7:58 pm, Nick Gasson wrote:
> Hi David,
> 
> On 01/24/20 14:35 pm, David Holmes wrote:
>>>
>>> How about we align the size up to ADDRESS_SIZE (== HeapWordSize) in
>>> Unsafe.allocateMemory() before the call to allocateMemoryChecks(). Like:
>>>
>>>     bytes = ((bytes + ADDRESS_SIZE - 1) & ~(ADDRESS_SIZE - 1));
>>>
>>> Then it will throw an IllegalArgumentException if the result is outside
>>> the size_t range. And in the native code we can just assert that the
>>> `size' argument is already aligned:
>>>
>>>     assert(is_aligned(sz, HeapWordSize), "sz not aligned");
>>
>> That seems quite reasonable.
>>
> 
> I've done this here:
> 
> http://cr.openjdk.java.net/~ngasson/8237521/webrev.02/
> 
> Need to check bytes >= 0 before aligning up so that allocateMemory(-1)
> still throws an IllegalArgumentException.

That looks good to me.

> Tested with jdk_foreign and runtime/Unsafe/.

Probably needs a bit more testing. IIRC the direct buffers use this API 
so they would be a good test subject. Or perhaps Maurizio can run this 
through our CI tier1-3 before pushing?

Thanks,
David

> 
> Thanks,
> Nick
>