RFR: JDK-8136893: Improve early java.lang.invoke infrastructure initialization

Peter Levart peter.levart at gmail.com
Fri Sep 25 15:19:02 UTC 2015

Hi Paul,

Thanks for looking into this.

On 09/25/2015 04:07 PM, Paul Sandoz wrote:
> Hi,
> This looks like a partial dup of https://bugs.openjdk.java.net/browse/JDK-8076596

Ah, sorry, I wasn't aware this has already been registered in JIRA. I 
have linked the two issues together as DUPs.

> The changes look ok, but I am concerned post initialization there may be code paths taken that require the system class loader to be used but instead the boot stream class loader is used instead. Is that a legitimate concern?

It is legitimate, but I have inspected usages and:

- In java.lang.invoke.BoundMethodHandle.Factory#makeCbmhCtor, null is 
passed explicitly and this method is used only from 
java.lang.invoke.BoundMethodHandle.Factory#makeCtors which is used from 
java.lang.invoke.BoundMethodHandle.SpeciesData#initForBootstrap and 
java.lang.Class<? extends java.lang.invoke.BoundMethodHandle>). These 
usages only deal with erased MH types (Object, long, int, double, float).

- In java.lang.invoke.MemberName#getMethodType, the result of 
MemberName.getClassLoader() is passed to the method. This is the class 
loader of the member's declaring class. Any types referenced from the 
member declaration should be resolvable from this class loader. A member 
declared by a bootstrap class (MemberName.getClassLoader() returns null) 
can only reference types resolvable from bootstrap loader.

- In java.lang.invoke.MemberName#getFieldType, the result of 
MemberName.getClassLoader() is passed to the method. Similar applies as 

- In java.lang.invoke.MethodHandleNatives#fixMethodType(Class<?> 
callerClass, Object type), the callerClass.getClassLoader() is passed to 
the method. This is invoked from:
                                      Class<?> callerClass, int refKind,
                                      Class<?> defc, String name, Object 
                                      Object[] appendixResult)
which is called from 
java.lang.invoke.MethodHandleNatives#linkMethod(same args)

I suppose this is an upcall from VM to link a call to the 
@PolymorphicSignature method and callerClass is the class in which the 
invocation bytecodes are executed. Am I right? The reasoning is as 
follows: if callerClass.getClassLoader() is sufficient for resolving 
types that appear at the call site in a non-bootstrap callerClass, then 
bootstrap classloader should be sufficient to resolve types that appear 
at the call site in a bootstrap callerClass. Does anybody have any other 

- sun.invoke.util.BytecodeDescriptor#parseMethod(java.lang.String, 
java.lang.ClassLoader) is only used from the newly introduced 

Regards, Peter

> Paul.
> On 25 Sep 2015, at 15:37, Michael Haupt <michael.haupt at oracle.com> wrote:
>> Hi Peter,
>> thanks for this changeset. Note I'm not a Reviewer (with a capital R); please read this review in lower-case. ;-)
>> One question about MethodType: would you mind doing something about the naming of the newly introduced fromDescriptor() method? Its name does not suggest in any way that it chooses the class loader differently. The name is subtly different from that of fromDescriptorString(), and the signature is identical - it's probably really easy to confuse the two when working at the core libs level. Unfortunately, the only proposal for a name I can make, fromDescriptorStringBootCL(), is clunky. Maybe that's acceptable for a low-level method only visible at package level.
>>> Am 25.09.2015 um 08:46 schrieb Peter Levart <peter.levart at gmail.com>:
>>> I have run the tests in java.lang.invoke and only have a problem with 1 test which seems to be related to the test or jtreg itself and happens also without my patch applied:
>>> #Test Results (version 2)
>>> #Tue Sep 22 09:48:38 CEST 2015
>>> ...
>>> #section:script_messages
>>> ----------messages:(0/0)----------
>>> test result: Error. Parse Exception: `@library' must appear before first `@run'
>> Yes. The test is also marked as ignored until another issue is fixed, so that can be ignored.
>> Other than the above remark/suggestion, this looks fine. I'll defer to an upper-case Reviewer, though.
>> Best,
>> Michael
>> --
>> <http://www.oracle.com/>
>> Dr. Michael Haupt | Principal Member of Technical Staff
>> Phone: +49 331 200 7277 | Fax: +49 331 200 7561
>> Oracle Java Platform Group | LangTools Team | Nashorn
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