On Thu, 13 May 2021 13:24:17 GMT, Kevin Walls <[email protected]> wrote:
>> This change enables debug.cpp's find() utility to print Java Objects with
>> their fields.
>>
>> find() calls os::print_location, and Java heap objects are printed with
>> instanceKlass oop_print_on.
>> Removing the ifdef for defining oop_print_on for instanceKlass, and also on
>> methods in FieldPrinter and FieldDescriptor, make this work.
>>
>>
>> Checking other uses of os::print_location this might affect:
>>
>> macroAssembler_x86.cpp has MacroAssembler::print_state32 and
>> MacroAssembler::print_state64
>> which use os::print_location to print register contents and print words at
>> top of stack.
>> These will be more verbose, as it already is in non-PRODUCT builds.
>>
>> vmError uses os::print_location when showing the stack, i.e. this output:
>>
>> Stack slot to memory mapping:
>> stack at sp + 0 slots: 0x0000000000000002 is an unknown value
>> ..etc...
>>
>> ...will be more verbose when Java object references are found (for the 8
>> stack slots it tries to show).
>>
>>
>> Shenandoah uses os::print_location once, but for non-Java heap objects so
>> nothing changes.
>>
>>
>> Manual testing on Linux-x64 and Windows: old behaviour shows these two lines
>> only:
>>
>> "Executing find"
>> 0x00000000ff0a03e0 is an oop: jdk.internal.loader.ClassLoaders$AppClassLoader
>> {0x00000000ff0a03e0} - klass:
>> 'jdk/internal/loader/ClassLoaders$AppClassLoader'
>>
>> ...then with the change the full info:
>>
>> "Executing find"
>> 0x00000000ff0a03e0 is an oop: jdk.internal.loader.ClassLoaders$AppClassLoader
>> {0x00000000ff0a03e0} - klass:
>> 'jdk/internal/loader/ClassLoaders$AppClassLoader'
>> - ---- fields (total size 13 words):
>> - private 'defaultAssertionStatus' 'Z' @12 false
>> - private final 'parent' 'Ljava/lang/ClassLoader;' @24 a
>> 'jdk/internal/loader/ClassLoaders$PlatformClassLoader'{0x00000000ff0a0a
>> 40} (ff0a0a40)
>> - private final 'name' 'Ljava/lang/String;' @28 "app"{0x00000000ff0d0060}
>> (ff0d0060)
>> - private final 'unnamedModule' 'Ljava/lang/Module;' @32 a
>> 'java/lang/Module'{0x00000000ff0a0448} (ff0a0448)
>> ...etc...
>
> Kevin Walls has updated the pull request incrementally with one additional
> commit since the last revision:
>
> ifdef correction
Hi Kevin,
The fix looks okay to me.
Thanks,
Serguei
-------------
Marked as reviewed by sspitsyn (Reviewer).
PR: https://git.openjdk.java.net/jdk/pull/4011
