On 03/06/2014 01:24 AM, David Holmes wrote:
On 6/03/2014 3:22 AM, Remi Forax wrote:
On 03/05/2014 06:07 PM, Peter Levart wrote:
On 03/05/2014 05:55 PM, Jeroen Frijters wrote:
Brian Goetz wrote:
I suspect you were expecting this response: we don't add language
semantics through annotations.
Technically, we're not adding language semantics. The JVM is the one
interpreting the annotations.
And the JVM is the one implementing the language semantics (together
with javac which feeds the JVM with bytecodes). Language semantcis are
implemented by the combination of javac and JVM. If you say that this
feature does not require any change to javac, you're just saying that
you put all the burden on the JVM, but you *are* implementing the
language semantics using annotations nevertheless...
no, it's the other way around. javac maps Java the language to the
bytecode semantics.
The JVM only execute bytecodes.
But if the JVM acts upon annotations to change how it executes those
bytecodes then, as Peter said, the JVM is implementing the language
semantics.
no, there is no bytecode in the proposal of Jeroen.
You can see it has an extended way to call in a VM intrinsic, currently
in Hotspot, you have to provide the class name, the method name and the
signature to consider a method as an intrinsic. The mechanism proposed
by Jeroen is a little bit more general.
Moreover, the proposal is interesting because the signature of the
native method is under the control of the user so unlike Unsafe
equivalent the signature can be verified when the native method is
linked making the method safer than their unsafe equivalent.
It is also a bit misleading to say that the JVM only executes
bytecodes, as the semantics of those bytecodes were driven by the
requirements of the language. javac + jvm do form a team here.
Most of the bytecodes are standard opcodes, but you're right that some
of them like method calls, instance creation or to a lesser extent
get[put]Field/get[put]Static have the Java semantics bolt in, that's why
we have invokedynamic (and Unsafe.get/put) BTW.
David
Rémi
Regards, Peter
cheers,
Rémi
I'm not trying to frustrate you; evolving a language with millions of
users is really, really hard. And one of the things that makes it
hard
is recognizing our intrinsic conflicts of interest between "what good
will this do me" and "what harm will it do others."
I understand, that's why I want to avoid adding language support for
this niche/specialist feature.
Regards,
Jeroen
