Apparant bug in the JVM

[Rickard Bäckman]

Stephen,

it's been fixed in b115.
Bug: JDK-8027622

Thanks
/R

On 11/11, Stephen Colebourne wrote:
> I was sent this piece of test code by Dirk Lemmermann. It fails
> randomly on JDK8 b114
> 
> import static java.time.temporal.ChronoUnit.DAYS;
> import java.time.Instant;
> 
> public class TestInstantBug {
>         public static void main(String[] args) {
>                 Instant now = Instant.now();
>                 System.out.println("now = " + now);
>                 for (int i = 0; i < 100000; i++) {
>                         System.out.println(i);
>                         Instant truncated = now.truncatedTo(DAYS);
>                         System.out.println(truncated);
>                 }
>         }
> }
> 
> The code does not change any variables during the loop. Instant is
> immutable and well written to my knowledge.
> 
> My debugging shows some horrible behaviour.
> 
> I copied Instant.java and edited it, adding it to the bootclasspath.
> This is the original code in Instant.java:
>     private static Instant create(long seconds, int nanoOfSecond) {
>         if ((seconds | nanoOfSecond) == 0) {
>             return EPOCH;
>         }
>         if (seconds < MIN_SECOND || seconds > MAX_SECOND) {
>             throw new DateTimeException("Instant exceeds minimum or
> maximum instant");
>         }
>         return new Instant(seconds, nanoOfSecond);
>     }
> 
> The second if statement randomly fails.
> Worse, the use of a System.out.println() on the "seconds" variable
> causes the if statement to reset.
> 
> Given this test code:
> 
>     private static Instant create(long seconds, int nanoOfSecond) {
>         if ((seconds | nanoOfSecond) == 0) {
>             return EPOCH;
>         }
>         System.out.println(seconds < MIN_SECOND || seconds > MAX_SECOND);
>         if (seconds < MIN_SECOND || seconds > MAX_SECOND) {
>             System.out.println(MIN_SECOND);
>             System.out.println(MAX_SECOND);
>             System.out.println(seconds);
>             System.out.println(seconds < MIN_SECOND);
>             System.out.println(seconds > MAX_SECOND);
>             System.out.println(seconds < MIN_SECOND || seconds > MAX_SECOND);
>             System.out.println("Create " + seconds);
>             System.out.println(MIN_SECOND);
>             System.out.println(MAX_SECOND);
>             System.out.println(seconds);
>             System.out.println(seconds < MIN_SECOND);
>             System.out.println(seconds > MAX_SECOND);
>             System.out.println(seconds < MIN_SECOND || seconds > MAX_SECOND);
>             throw new DateTimeException("Instant exceeds minimum or
> maximum instant");
>         }
>         return new Instant(seconds, nanoOfSecond);
>     }
> 
> the output is (when it actually fails):
> true   // the if statement randomly returned true
> -31557014167219200
> 31556889864403199
> 1384128000
> false  // the two parts of the if statement return false
> false  // the two parts of the if statement return false
> true   // the if statement still returns true
> Create 1384128000  // system out resets it
> -31557014167219200
> 31556889864403199
> 1384128000
> false
> false
> false   // the if statement returns false
> Exception in thread "main" java.time.DateTimeException: Instant
> exceeds minimum or maximum instant
>     at java.time.Instant.create(Instant.java:422)
>     at java.time.Instant.ofEpochSecond(Instant.java:327)
>     at java.time.Instant.plus(Instant.java:940)
>     at java.time.Instant.plusNanos(Instant.java:918)
>     at java.time.Instant.truncatedTo(Instant.java:773)
>     at TestInstantBug.main(TestInstantBug.java:13)
>     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>     at java.lang.reflect.Method.invoke(Method.java:483)
>     at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
> 
> Hope you can squash this bug. b114 needs a big warning sign on it.
> 
> Stephen