RFR: 8031686: G1: assert(_hrs.max_length() == _expansion_regions) failed

[Thomas Schatzl]

Hi Stefan,

On Thu, 2014-01-16 at 14:43 +0100, Stefan Johansson wrote:
> Hi,
> 
> Please review this small fix for:
> https://bugs.openjdk.java.net/browse/JDK-8031686
> 
> Webrev:
> http://cr.openjdk.java.net/~sjohanss/8031686/webrev.00/
> 
> Summary:
> The failing assertion is caused by an erroneous calculation done when 
> setting up the regions array in HeapRegionSeq. When using a large heap a 
> pointer calculation will overflow (since ptrdiff_t is signed) and this 
> will in turn lead to the regions array being created longer that it 
> should be. For non debug builds this will lead to increased memory usage 
> and jmap will report a faulty value for the number of regions. The fix 
> is to use the pointer_delta-function to do the calculation.

Looks good.

Thanks for fixing this,
Thomas