Code review request for 8012044: Give more information about self-suppression from Throwable.addSuppressed

[Jason Mehrens]

Joe,
You'll have guard ise.addSuppressed against null.  Looks good otherwise.

private static void initCauseNull() {
     Throwable t1 = new Throwable();
     t1.initCause(null);
     try {
       t1.initCause(null);
     } catch(IllegalStateException expect) {
     }
}

Jason
 
Date: Fri, 12 Apr 2013 12:08:07 -0700
From: joe.darcy at oracle.com
To: jason_mehrens at hotmail.com
CC: core-libs-dev at openjdk.java.net
Subject: Re: Code review request for 8012044: Give more information about self-suppression from Throwable.addSuppressed
On 04/12/2013 11:22 AM, Jason Mehrens wrote:

The landmines are the retrofitted exception classes as shown here https://netbeans.org/bugzilla/show_bug.cgi?id=150969 and https://issues.jboss.org/browse/JBREM-552. Really, if the ISE or IAE is thrown it is going to suppress 'this' and 'cause'. It would be nice to see the given 'cause' show up in a log file when tracking down this type of bug. 
Okay; fair enough. Updated webrev covering initCause too at
 http://cr.openjdk.java.net/~darcy/8012044.1/
 New patch below.
 (It is a bit of stretch to have this in initiCause by listed as the "cause" of the IllegalStateException; as an alternative, the IllegalStateException could have both this and the cause as suppressed exceptions.)
 Cheers,
 -Joe
 --- old/src/share/classes/java/lang/Throwable.java 2013-04-12 12:03:48.000000000 -0700
 +++ new/src/share/classes/java/lang/Throwable.java 2013-04-12 12:03:48.000000000 -0700
 @@ -452,10 +452,14 @@
 * @since 1.4
 */
 public synchronized Throwable initCause(Throwable cause) {
 - if (this.cause != this)
 - throw new IllegalStateException("Can't overwrite cause");
 + if (this.cause != this) {
 + IllegalStateException ise =
 + new IllegalStateException("Can't overwrite cause", this);
 + ise.addSuppressed(cause);
 + throw ise;
 + }
 if (cause == this)
 - throw new IllegalArgumentException("Self-causation not permitted");
 + throw new IllegalArgumentException("Self-causation not permitted", this);
 this.cause = cause;
 return this;
 }
 @@ -1039,7 +1043,7 @@
 */
 public final synchronized void addSuppressed(Throwable exception) {
 if (exception == this)
 - throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE);
 + throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE, exception);
 if (exception == null)
 throw new NullPointerException(NULL_CAUSE_MESSAGE);
 --- old/test/java/lang/Throwable/SuppressedExceptions.java 2013-04-12 12:03:49.000000000 -0700
 +++ new/test/java/lang/Throwable/SuppressedExceptions.java 2013-04-12 12:03:48.000000000 -0700
 @@ -26,7 +26,7 @@
 /*
 * @test
 - * @bug 6911258 6962571 6963622 6991528 7005628
 + * @bug 6911258 6962571 6963622 6991528 7005628 8012044
 * @summary Basic tests of suppressed exceptions
 * @author Joseph D. Darcy
 */
 @@ -40,6 +40,7 @@
 serializationTest();
 selfReference();
 noModification();
 + initCausePlumbing();
 }
 private static void noSelfSuppression() {
 @@ -48,7 +49,9 @@
 throwable.addSuppressed(throwable);
 throw new RuntimeException("IllegalArgumentException for self-suppresion not thrown.");
 } catch (IllegalArgumentException iae) {
 - ; // Expected
 + // Expected to be here
 + if (iae.getCause() != throwable)
 + throw new RuntimeException("Bad cause after self-suppresion.");
 }
 }
 @@ -208,4 +211,29 @@
 super("The medium.", null, enableSuppression, true);
 }
 }
 +
 + private static void initCausePlumbing() {
 + Throwable t1 = new Throwable();
 + Throwable t2 = new Throwable("message", t1);
 + Throwable t3 = new Throwable();
 +
 + try {
 + t2.initCause(t3);
 + throw new RuntimeException("Shouldn't reach.");
 + } catch (IllegalStateException ise) {
 + if (ise.getCause() != t2)
 + throw new RuntimeException("Unexpected cause in ISE", ise);
 + Throwable[] suppressed = ise.getSuppressed();
 + if (suppressed.length != 1 || suppressed[0] != t3)
 + throw new RuntimeException("Bad suppression in ISE", ise);
 + }
 +
 + try {
 + t3.initCause(t3);
 + throw new RuntimeException("Shouldn't reach.");
 + } catch (IllegalArgumentException iae) {
 + if (iae.getCause() != t3)
 + throw new RuntimeException("Unexpected cause in ISE", iae);
 + }
 + }
 }