New protocol for disabling exception suppression

[Rémi Forax]

On 04/03/2011 04:28 AM, David Holmes wrote:
> Rémi Forax said the following on 04/03/11 11:52:
>> On 04/02/2011 03:21 AM, joe.darcy at oracle.com wrote:
>>> As part of the library support for the try-with-resources statement,
>>> several API changes were made to Throwable including an addSuppressed
>>> method to allow suppressed exceptions to be recorded. As previously
>>> discussed on coin-dev [1], to support VM needs for reusable exception
>>> objects, a protocol was devised to disable the suppression mechanism so
>>> that a zero-length array would be returned from getSuppressed even if
>>> addSuppressed was called with a valid argument. The mechanism was a bit
>>> of a kludge, relying on an initial call to addSuppressed with a null
>>> argument, and the design was called out as such. [2] I'm happy to 
>>> report
>>> the JSR 334 expert group has devised a more elegant protocol to disable
>>> exception suppression: a new constructor is added to Throwable which
>>> supports disabling suppression. The existing constructors of Throwable
>>> always enable suppression and addSuppressed(null) now always throws a
>>> NullPointerException. A few exception and error types in the platform
>>> are allowed by behave as if their objects were created with suppression
>>> disabled.
>>>
>>> The fix was recently pushed [3] and will appear in a future JDK 7 
>>> build.
>>>
>>> -Joe
>>>
>>> [1] 
>>> http://mail.openjdk.java.net/pipermail/coin-dev/2010-August/002830.html
>>> [2]
>>> http://mail.openjdk.java.net/pipermail/coin-dev/2010-October/thread.html#2920 
>>>
>>> [3] http://hg.openjdk.java.net/jdk7/tl/jdk/rev/856cc9e97aea
>>>
>>
>> So the code of the VM was changed to call the constructor if it exists ?
>
> No. The VM never calls a constructor it just allocates zeroed memory - 
> which has the same affect as calling the new constructor.
>
> David

So I don't see the improvement ?

Rémi