Request for review (XXS): JDK-8004066: TEST_BUG: test/java/lang/Math/DivModTests.java assumes ArithmeticException message

[Krystal Mo]

Hi all,

Could I get a couple of review for this small change, please?
And could someone from the JDK side sponsor this change?

Bug: https://jbs.oracle.com/bugs/browse/JDK-8004066
Webrev: http://cr.openjdk.java.net/~kmo/8004066/webrev.00/

The DivModTest introduced in JDK-6282196 [1] checks the contents of the 
exception message, but that message isn't specified in JavaDoc and thus 
may vary between VM implementations (or even in the same VM).

The issue has affected HotSpot Server VM in nightlies, and the Shark VM. 
As OpenJDK library code may receive broader adoption in the future, this 
issue may affect other VM implementations in the future as well.

(Details:
The HotSpot Server Compiler may recompile hot throw sites to throw a 
preallocated exception object, with null exception message, leading to a 
NPE in the test;
The bytecode interpreter in Zero/Shark VM throws the ArithmeticException 
with "/ by long zero" for ldiv, which is different from normal HotSpot 
behavior (which is expected by the test) where the exception message is 
"/ by zero".)

This change relaxes the test so that it's more lenient and less 
sensitive to the error message produced by the VM.
I don't think there's a good/reliable way of verifying whether an 
ArithmeticException came from "division by zero", checking the type 
should be enough for now.

Tested with the failing nightly test case and jprt.

$ java -Xcomp -showversion -XX:DefaultMaxRAMFraction=8 
-XX:-TieredCompilation -XX:CompileThreshold=100 
-XX:+UnlockExperimentalVMOptions -XX:+IgnoreUnrecognizedVMOptions 
-XX:+AggressiveOpts -XX:+IgnoreUnrecognizedVMOptions 
-XX:-UseCompressedOops DivModTests
java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b65)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b11-internal-fastdebug, 
compiled mode)

Exception in thread "main" java.lang.NullPointerException
     at DivModTests.resultEquals(DivModTests.java:390)
     at DivModTests.testIntFloorMod(DivModTests.java:126)
     at DivModTests.testIntFloorDivMod(DivModTests.java:103)
     at DivModTests.testIntFloorDivMod(DivModTests.java:68)
     at DivModTests.main(DivModTests.java:45)


Description from the bug report:
~/jdk/test/java/lang/Math$ java -Xint -showversion DivModTests
java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b65)
OpenJDK 64-Bit Shark VM (build 25.0-b11-internal, interpreted mode)

FAIL: long Math.floorDiv(4, 0) = java.lang.ArithmeticException: / by 
long zero; expected java.lang.ArithmeticException: / by zero
FAIL: long StrictMath.floorDiv(4, 0) = java.lang.ArithmeticException: / 
by long zero; expected java.lang.ArithmeticException: / by zero
FAIL: long Math.floorMod(4, 0) = java.lang.ArithmeticException: / by 
long zero; expected java.lang.ArithmeticException: / by zero
FAIL: long StrictMath.floorMod(4, 0) = java.lang.ArithmeticException: / 
by long zero; expected java.lang.ArithmeticException: / by zero
Exception in thread "main" java.lang.RuntimeException: 4 errors found in 
DivMod methods.
at DivModTests.main(DivModTests.java:49)

Regards,
Kris

[1]: https://jbs.oracle.com/bugs/browse/JDK-6282196