RFR: JDK-8282144 RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes

[Brian Burkhalter]

On Sun, 27 Feb 2022 22:30:44 GMT, Jim Laskey <jlaskey at openjdk.org> wrote:

>> test/jdk/java/util/Random/T8282144.java line 39:
>> 
>>> 37: public class T8282144 {
>>> 38:     public static void main(String[] args) {
>>> 39:         RandomGenerator rng = RandomGeneratorFactory.of("L64X128MixRandom").create(42);
>> 
>> Does `rng` always produce the same sequence? If so, then perhaps the seed, `42`, should be a random value that is printed.
>
> 42 was chosen because its is known to produce negative byte values, other random values might not.

OK

>> test/jdk/java/util/Random/T8282144.java line 52:
>> 
>>> 50:                 for (int k = 0; k < existing.length; k++) {
>>> 51:                     if (existing[k] != testing[k]) {
>>> 52:                         throw new RuntimeException("convertSeedBytesToLongs incorrect");
>> 
>> Should `i`, `j`, and `k` be included in the exception message?
>
> Correctness is binary - either it works or it doesn't. The values of i, j, k would not assist in isolating issues. Might add to confusion if displayed.

Understood.

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PR: https://git.openjdk.java.net/jdk/pull/7614