Anonymous class

[David Holmes]

On 25/01/2019 11:06 pm, yumin qi wrote:
> Hi, David
> 
> I am confused here.
> As you pointed out:
>     Java anonymous classes are not VM anonymous classes.
>     VM anonymous classes are created by Unsafe_DefineAnonymousClass only.
> 
> Is my understanding right? All all lambda classes are vm anonymous?

I don't know if it is correct to say "all lambda classes" as I don't 
know the full translation strategy for lambda expressions, but yes some 
lambda generated classes are VM anonymous classes.

David

> Thanks
> Yumin
> 
> On Fri, Jan 25, 2019 at 7:18 PM David Holmes <david.holmes at oracle.com 
> <mailto:david.holmes at oracle.com>> wrote:
> 
>     <dropped jdk-dev>
> 
>     On 25/01/2019 6:52 pm, yumin qi wrote:
>      > Hi,
>      >
>      >    I have a question of anonymous class. We know the anonymous
>     class with a
>      > host_klass, and the flag is set when the InstanceKlass is created
>     after the
>      > class parsed. In case of a regular java class file, the flag will
>     be set
>      > correctly but for the case it is not set:
>      >    SystemDictionary::parse_stream or resolve_from_stream, which
>     is called
>      > from JVM_DefineClassWithSource or jni_defineClass. The stack
>     trace like:
>      >
>      > #1  0x00007f1127291ce7 in
>      > SystemDictionary::resolve_from_stream(class_name=0x7f0ee40243f0,
>      > class_loader=..., protection_domain=...,d__=0x7f0f04001000) at
>      >
>     /home/ws/openjdk/8/jdk8u/hotspot/src/share/vm/classfile/systemDictionaryShared.cpp:656
>      > #1  0x00007f1127291ce7 in SystemDictionary::resolve_from_stream
>      > (class_name=0x7f0ee40243f0, class_loader=..., protection_doma
>      > in=...,
>      >      st=0x7f0f0a5f3850, verify=true, __the_thread__=0x7f0f04001000)
>      >      at
>      >
>     /home/ws/openjdk/8/jdk8u/hotspot/src/share/vm/classfile/systemDictionary.cpp:1234
>      > #2  0x00007f1126f3cadb in jvm_define_class_common
>     (env=0x7f0f04001220,
>      > name=0x7f0f0a5f3e60 "com/google/common/collect/Iterato
>      > rs$3",
>      >      loader=0x7f0f0a5f3f20, buf=0x7f0ee401e210
>     "\312\376\272\276", len=943,
>      > pd=0x7f0f0a5f3f48,
>      >      source=0x7f0f0a5f3a60
>     "jar:file:/home/<...>/lib/guava-19.0.jar!/",
>      > verify=1 '\001', __the_thread__=0x7f0f04001000) at
>      >
>     /home/yumin.qi/ws/openjdk/8/jdk8u/hotspot/src/share/vm/prims/jvm.cpp:1082
>      > #3  0x00007f1126f3d019 in JVM_DefineClassWithSource
>     (env=0x7f0f04001220,
>      > name=0x7f0f0a5f3e60 "com/google/common/collect/Itera
>      > tors$3",
>      >      loader=0x7f0f0a5f3f20, buf=0x7f0ee401e210
>     "\312\376\272\276", len=943,
>      > pd=0x7f0f0a5f3f48,
>      >      source=0x7f0f0a5f3a60
>     "jar:file:/home/<...>/lib/guava-19.0.jar!/") at
>      > /home/ws/openjdk/8/jdk8u/hotspot/src/share/vm/prim/jvm.cpp:1102
>      > #4  0x00007f112581214f in Java_java_lang_ClassLoader_defineClass1 ()
>      >     from
>      >
>     /home/ws/openjdk/8/jdk8u/build/linux-x86_64-normal-server-slowdebug/images/j2sdk-image/jre/lib/amd64/libjava.so
>      > #5  0x00007f11118f5402 in ?? ()
>      > #6  0x00007f0f0a5f3f48 in ?? ()
>      > #7  0x00007f0f0a5f3f70 in ?? ()
>      > #8  0x0000000755dbbc28 in ?? ()
>      >
>      > The class name is com.google.common.collect.Iterators$3, and it is an
>      > anonymous class.
> 
>     I'm confused. Are you talking about Java level anonymous classes or VM
>     anonymous classes as created by Unsafe.defineAnonymousClass? Only VM
>     anonymous classes have a "host class". Java level "anonymous classes"
>     are just regular classes.
> 
>     David
>     -----
> 
> 
> 
>      > This is an example using Guava. I also can reproduce with jdk13.
>      >
>      > The field after parsing:
>      >
>      >   _nonstatic_oop_map_size = 1,
>      >    _is_marked_dependent = false,
>      >    _has_unloaded_dependent = false,
>      >    _misc_flags = 38,      ////// <------------ not set for anonymous
>      >    _minor_version = 0,
>      >    _major_version = 50,
>      >    _init_thread = 0x0,
>      >    _vtable_len = 8,
>      >    _itable_len = 8,
>      >
>      >    This path is from a custom loader defining a anonymous class,
>     does not
>      > set anonymous correctly for the flag. Is this a bug? If in java land,
>      > supply a host as parameter,  it can be set correctly in VM part.
>     Should I
>      > file a bug for it?
>      >
>      > Thanks
>      > Yumin
>      >
>