On the EagerInitialization VM flag

[Bertrand Delsart]

Hi all,

I was in fact looking at EagerInitialization code when I saw this e-mail 
thread :-)

It might be useful at least for some research projects. As long as it is 
'develop' flag turned off in the product, I don't see strong reasons to 
remove the code... and we may end up finding good ways of using it !

Thanks,

Bertrand.

On 20/12/13 01:06, Krystal Mok wrote:
> Hi David,
>
> Comments inline below:
>
> On Thu, Dec 19, 2013 at 3:52 PM, David Holmes <david.holmes at oracle.com
> <mailto:david.holmes at oracle.com>> wrote:
>
>     On 20/12/2013 12:18 AM, Krystal Mok wrote:
>
>         Hi David,
>
>         Thanks for the reply, David.
>
>         When turned on, EagerInitialization is only applied to those classes
>         that doesn't have a <clinit>()V, which is the case for quite some
>         classes and interfaces. If implemented correctly, it's supposed
>         to be
>         semantically safe, because executing a non-existing initializer
>         shouldn't cause side effects visible from the Java level (but doing
>         linking and verification at the wrong time is potentially
>         problematic,
>         though).
>
>
>     Oops! My brain insisted this:
>
>         // abort if the the class has a class initializer
>          if (this->class_initializer() != NULL) return;
>
>     was there to skip if there wasn't a class initializer! So everything
>     I said was wrong.
>
>     This would better be called EagerLinking as it has nothing to do
>     with class initialization in the <clinit> sense.
>
> It is still valid as EagerInitialization, because in the end the class's
> status will be set to "initialized", so that on first actual use of this
> class it'll be magically "initialized" already and doesn't have to do
> all the checking and stuff.
>
> Thanks,
> Kris
>
>     I believe both loading and linking (and thus verification) can be
>     performed eagerly.
>
>     David
>     -----
>
>         I wasn't intending to purpose removing the flag and its
>         implementation,
>         but I'd agree if someone did make such proposal.
>
>         - Kris
>
>
>         On Thu, Dec 19, 2013 at 4:26 PM, David Holmes
>         <david.holmes at oracle.com <mailto:david.holmes at oracle.com>
>         <mailto:david.holmes at oracle.__com
>         <mailto:david.holmes at oracle.com>>> wrote:
>
>              On 14/12/2013 7:56 AM, Krystal Mok wrote:
>
>                  Which is of course true, but not what I really cared about.
>                  I'm just curious of the history of what that flag tried
>         to do,
>                  and then
>                  why didn't it work. Any pointers or hints would be
>         appriciated.
>
>
>              Given its age it is hard to say why it wasn't removed at
>         the time
>              4292939 indicated. What it does is force class
>         initialization at
>              class loading time. This might have been seen as useful at some
>              point but it violates the Java language semantics regarding
>         when
>              class initialization can occur (eager loading is allowed, eager
>              initialization is not).
>
>              Given eager initialization is likely to break the carefully
>         crafted
>              class initialization sequence I don't really see its
>         utility - hence
>              the proposal to remove it.
>
>              David
>
>                  Thanks,
>                  Kris
>
>                  On Friday, December 13, 2013, Christian Thalinger wrote:
>
>                       Well, it’s a develop flag so it cannot be used in the
>                  product anyway.
>
>                       On Dec 13, 2013, at 11:27 AM, Krystal Mok
>                  <rednaxelafx at gmail.com <mailto:rednaxelafx at gmail.com>
>         <mailto:rednaxelafx at gmail.com <mailto:rednaxelafx at gmail.com>>
>
>                       <javascript:_e({}, 'cvml', 'rednaxelafx at gmail.com
>         <mailto:rednaxelafx at gmail.com>
>                  <mailto:rednaxelafx at gmail.com
>         <mailto:rednaxelafx at gmail.com>>__');>> wrote:
>
>                           Hi all,
>
>                           Does anybody still remember the history behind the
>                           -XX:+EagerInitialization flag? It'd be great
>         if someone
>                      still
>                           knows what the flag was for, and why it was to
>         be removed.
>
>                           I saw this bug:
>         https://bugs.openjdk.java.net/____browse/JDK-4292939
>         <https://bugs.openjdk.java.net/__browse/JDK-4292939>
>
>                      <https://bugs.openjdk.java.__net/browse/JDK-4292939
>         <https://bugs.openjdk.java.net/browse/JDK-4292939>>
>                           which stated that this flag was going away in
>         "the next
>                      build",
>                           but now it's still in the code.
>
>                           Thanks,
>                           Kris
>
>
>
>