RFR: 8264976: Minor numeric bug in AbstractSplittableWithBrineGenerator.makeSplitsSpliterator

[Aleksey Shipilev]

On Fri, 9 Apr 2021 09:41:19 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> SonarCloud reports:
>   Cast one of the operands of this subtraction operation to a "long".
> 
> Here:
> 
>         Spliterator<SplittableGenerator> makeSplitsSpliterator(long index, long fence, SplittableGenerator source) {
>             ...
>             long multiplier = (1 << SALT_SHIFT) - 1; // <---- here
> 
> 
> The shift is integer, and the implicit cast to `long` happens too late. `SALT_SHIFT` is currently 4, so this is not the problem yet. But it would become a problem if `SALT_SHIFT` ever becomes 32 or larger. The shift operand should be `1L` for safety. Observe:
> 
> 
> jshell> Long.toHexString((1 << 31) - 1)
> $2 ==> "7fffffff"
> 
> jshell> Long.toHexString((1 << 32) - 1)
> $3 ==> "0"
> 
> jshell> Long.toHexString((1L << 32) - 1)
> $4 ==> "ffffffff"
> 
> 
> Additional testing: 
>  - [x] Linux x86_64 fastdebug, `jdk/utils/Random`

Anyone? :)

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PR: https://git.openjdk.java.net/jdk/pull/3409