MethodHandle.invoke* should only work with source 1.7

[Attila Szegedi]

I was actually doing this until yesterday for compiling the dynalink framework, and while the 1.6 javac did give me a warning and suggested I need a newer version of the compiler, it didn't stop with an error. When those classes were then loaded in an OpenJDK JVM, they nicely passed all tests. So funnily enough, I was able to work on it with the 1.6 compiler :-)

Of course, in my code, I never have actual invokedynamic call sites in the bytecode, it's all about direct MethodHandle manipulation.

Attila.

On Feb 10, 2011, at 3:03 PM, John Rose wrote:

> On Feb 10, 2011, at 3:46 AM, Rémi Forax wrote:
> 
>> The main problem is that when you will run it, with a 1.7 VM because 
>> MethodHandle is only available with a 1.7 VM,
>> the VM will throw a WrongMethodTypeException because as you said the 292 
>> magic will be ignored.
>> 
>> I think it's better for the users to don't compile instead of compiling 
>> something which is inherently wrong.
> 
> Try compiling mh.invokeExact using a 1.6 compiler against a 1.7 rt.jar.  You should get a compile-time error, since the class file version numbers are wrong.  The 1.6 compiler should refuse to load MethodHandle.class from rt.jar.
> 
> If you compile against a non-standard rt.jar, you might get the error you are observing, but that error won't affect 1.7 users.  If it affects backport users, I suggest taking steps to put the java.dyn package jar in a special place where the 1.6 compiler is not going to see it, by default.
> 
> There are lots of variations on this theme of version mismatches.  But the class file version number saves us in a lot of them.
> 
> -- John
> _______________________________________________
> mlvm-dev mailing list
> mlvm-dev at openjdk.java.net
> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev