SafeVarargs classfile encoding

[Rémi Forax]

On 01/21/2011 08:34 PM, Joe Darcy wrote:
> Rémi Forax wrote:
>> On 01/21/2011 07:50 PM, Joe Darcy wrote:
>>> Hi Rémi.
>>>
>>> A few comments, in the entirety of the "jdk" repository, there were 
>>> a total of five methods where it was appropriate to add this 
>>> annotation, which is not a very high density!  For Coin, to keep the 
>>> features small, we're avoiding JVM changes and defining a new 
>>> attribute is a JVM changes of sorts.
>>
>> Here is the JVM spec change:
>
> [snip]
>
> The size of the JVM change is not the problem; the fact that 
> potentially all class file consuming tools would need to know about 
> the attribute is.

No because it's an empty attribute. I will be ignored by classfile 
reader, and copied by classfile read/writer.
see section 4.7.1 of the VM spec.

>   Additionally, this would be a new kind of side-effect of annotating 
> a method.

I don't understand your point here.
SafeVarargs doesn't alter the semantics of a method for the VM,
like Deprecated or Synthetic which are already defined as attribute.

>
>>
>>>
>>> Using an annotation to store this information avoids the need to add 
>>> a new core reflection API to access it, Method.isSafeVarargs, etc.
>>
>> Why SafeVarargs need to be visible using reflection API ?
>
> Why should the information be excluded?  This annotation is a 
> statement about the semantics of the method.

This annotation doesn't alter the *runtime* semantics of a method.

>
>> By example, Synthetic attribute is not visible using reflection API.
>>
>
> Some synthetic information is exposed in core reflection:
>
> http://download.java.net/jdk7/docs/api/java/lang/Class.html#isSynthetic()
> http://download.java.net/jdk7/docs/api/java/lang/reflect/Constructor.html#isSynthetic() 
>
> http://download.java.net/jdk7/docs/api/java/lang/reflect/Method.html#isSynthetic() 
>
> http://download.java.net/jdk7/docs/api/java/lang/reflect/Field.html#isSynthetic() 
>

Ok, bad example.

>
> -Joe

Rémi