[12] RFR (M) JDK-8205611: Improve the wording of LinkageErrors to include module and class loader information

[Lindenmaier, Goetz]

Hi Lois, 

I had a look at your change. It's a much better format bearing the 
same information. Thus looks good to me.

I would appreciate if you change printing the messages in linkResolver.cpp and
klassVtable.cpp to use stringStream, similar to linkResolver.cpp:1020
and other places (I should have changed that in first place when
I extended these messages before).

systemDictionary.cpp
  I think it's convention to have a space after the comma:
  existing_klass->class_in_module_of_loader(false,true));
 This is in several places.

Best regards,
  Goetz.



> -----Original Message-----
> From: hotspot-dev [mailto:hotspot-dev-bounces at openjdk.java.net] On
> Behalf Of Lois Foltan
> Sent: Mittwoch, 27. Juni 2018 15:20
> To: hotspot-dev developers <hotspot-dev at openjdk.java.net>
> Subject: [12] RFR (M) JDK-8205611: Improve the wording of LinkageErrors to
> include module and class loader information
> 
> Please review this change to migrate existing loader constraint
> LinkageErrors to the new error message format proposal.  The actual
> wording of the loader constraint messages has not changed.  Module and
> class loader information have been moved into the error message's REASON
> section.  This change also removes the method
> java_lang_ClassLoader::describe_external() in favor of
> Klass::class_in_module_of_loader().
> 
> open webrev at
> http://cr.openjdk.java.net/~lfoltan/bug_jdk8205611/webrev/
> bug link https://bugs.openjdk.java.net/browse/JDK-8205611
> 
> JDK-8166633 outlines a new proposal where error messages follow a format
> of ERRROR: PROBLEM (REASON) where the PROBLEM is aggressively simple
> (and definitely avoids arbitrary-length loader names) so the REASON
> bears all the cost of explaining the PROBLEM with more specifics.  See
> the proposal in more detail at
> https://bugs.openjdk.java.net/browse/JDK-8166633. The new utility method
> Klass::class_in_module_of_loader() implements the proposed format.
> 
> Some example text:
> 
> (JDK 11) 'DuplicateLE_Test_Loader_IF' @<id> (instance of
> PreemptingClassLoader, child of 'app'
> jdk.internal.loader.ClassLoaders$AppClassLoader) attempted duplicate
> interface definition for test.J.
> to
> (JDK 12) loader 'DuplicateLE_Test_Loader_IF' @6eeee674 attempted
> duplicate interface definition for test.J. (test.J is in unnamed module
> of loader 'DuplicateLE_Test_Loader_IF' @6eeee674, parent loader 'app')
> 
> 
> (JDK 11) loader constraint violation: loader PreemptingClassLoader @<id>
> (instance of PreemptingClassLoader, child of 'app'
> jdk.internal.loader.ClassLoaders$AppClassLoader) wants to load class
> test.D_ambgs. A different class with the same name was previously loaded
> by 'app' (instance of jdk.internal.loader.ClassLoaders$AppClassLoader).
> to
> (JDK 12) loader constraint violation: loader PreemptingClassLoader
> @5bc79a1c wants to load class test.D_ambgs. A different class with the
> same name was previously loaded by 'app'. (test.D_ambgs is in unnamed
> module of loader 'app')
> 
> 
> (JDK 11) loader constraint violation for class test.Task: when selecting
> overriding method test.Task.m()Ltest/Foo; the class loader
> PreemptingClassLoader @<id> (instance of PreemptingClassLoader, child of
> 'app' jdk.internal.loader.ClassLoaders$AppClassLoader) of the selected
> method's type test.Task, and the class loader 'app' (instance of
> jdk.internal.loader.ClassLoaders$AppClassLoader) for its super type
> test.J have different Class objects for the type test.Foo used in the
> signature
> to
> (JDK 12) loader constraint violation for class test.Task: when selecting
> overriding method test.Task.m()Ltest/Foo; the class loader
> PreemptingClassLoader @7884e077 of the selected method's type test.Task,
> and the class loader 'app' for its super type test.J have different
> Class objects for the type test.Foo used in the signature (test.Task is
> in unnamed module of loader PreemptingClassLoader @7884e077, parent
> loader 'app'; test.J is in unnamed module of loader 'app')
> 
> 
> Testing: hs-tier(1-3), jdk-tier(1-3) complete
>                 hs-tier(4,5) in progress
>                 JCK vm, lang in progress
> 
> Thanks,
> Lois