RFR: 8221723: Avoid storing zero to String.hash

[Claes Redestad]

Hi Jiangli,

On 2019-04-01 17:21, Jiangli Zhou wrote:
> 
> 
> On Mon, Apr 1, 2019 at 4:59 AM Claes Redestad <claes.redestad at oracle.com 
> <mailto:claes.redestad at oracle.com>> wrote:
> 
>     Hi,
> 
>     when a String has a calculated hash code value of 0, we recalculate and
>     store a 0 to the String.hash field every time (except for the empty
>     String, which is special cased). To make String objects more amenable to
>     storage in shared read-only memory, e.g., CDS archives, we should avoid
>     this redundant store.
> 
> 
> That was exactly the reason why 0-hash string was excluded from the 
> closed archive heap region.

Thanks for confirming!

> 
> 
>     Bug: https://bugs.openjdk.java.net/browse/JDK-8221723
>     Webrev: http://cr.openjdk.java.net/~redestad/8221723/
> 
> 
> Looks good to me.

Thanks!

/Claes