RFR: 8292699: Improve printing of classes in native debugger [v7]

[Coleen Phillimore]

On Mon, 22 Aug 2022 18:42:35 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Current in gdb, you can print information about a class or method with something like
>> 
>> 
>> call ((InstanceKlass*)0x00000008000411b8)->print_on(tty)
>> call ((Method*)0x00007fffb4000d08)->print_codes_on(tty)
>> 
>> 
>> However, it's difficult to find a class or method by its name and print out its contents.
>> 
>> This RFE adds 3 new functions in debug.cpp so you can easily find classes/methods and print out their contents. They all have a `flags` argument that controls the verbosity.
>> 
>> - `findclass()`: class name only
>> - `findmethod()`: class name and method name
>> - `findmethod2()`: class name and method name/signature
>> 
>> I also cleaned up `BytecodeTracer` to remove unnecessary complexity.
>> 
>> Here are some examples:
>> 
>> 
>> (gdb) call findclass("java/lang/Object", 0)
>> [0] 0x00000008000411b8 java.lang.Object, loader data: 0x00007ffff0130d10 of 'bootstrap'
>> 
>> (gdb) call findclass("java/lang/Object", 1)
>> [0] 0x00000008000411b8 java.lang.Object, loader data: 0x00007ffff0130d10 of 'bootstrap'
>> 0x00007fffb4000658 <init> : ()V
>> 0x00007fffb40010f0 finalize : ()V
>> 0x00007fffb4000f00 wait0 : (J)V
>> 0x00007fffb40008e8 equals : (Ljava/lang/Object;)Z
>> 0x00007fffb4000aa0 toString : ()Ljava/lang/String;
>> 0x00007fffb40007f0 hashCode : ()I
>> 0x00007fffb4000720 getClass : ()Ljava/lang/Class;
>> 0x00007fffb40009a0 clone : ()Ljava/lang/Object;
>> 0x00007fffb4000b50 notify : ()V
>> 0x00007fffb4000c20 notifyAll : ()V
>> 0x00007fffb4000e50 wait : (J)V
>> 0x00007fffb4001028 wait : (JI)V
>> 0x00007fffb4000d08 wait : ()V
>> 
>> (gdb) call findclass("*ClassLoader", 0)
>> [0] 0x000000080007de40 jdk.internal.loader.ClassLoaders$BootClassLoader, loader data: 0x00007ffff0130d10 of 'bootstrap'
>> [1] 0x0000000800053c58 jdk.internal.loader.ClassLoaders$PlatformClassLoader, loader data: 0x00007ffff0130d10 of 'bootstrap'
>> [2] 0x0000000800053918 jdk.internal.loader.ClassLoaders$AppClassLoader, loader data: 0x00007ffff0130d10 of 'bootstrap'
>> [....]
>> 
>> (gdb) call findmethod2("*ang/Object*", "wait", "()V", 0x7)
>> [0] 0x00000008000411b8 java.lang.Object, loader data: 0x00007ffff0130d10 of 'bootstrap'
>> 0x00007fffb4000d08 wait : ()V
>> 0x00007fffb4000ce8 0 fast_aload_0
>> 0x00007fffb4000ce9 1 lconst_0
>> 0x00007fffb4000cea 2 invokevirtual 38 <java/lang/Object.wait(J)V>
>> 0x00007fffb4000ced 5 return
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use proper locking

I'm still trying to understand the need for new code for this but I have a couple of initial comments.

src/hotspot/share/interpreter/bytecodeTracer.cpp line 434:

> 432:     // TODO: print info for tag.is_dynamic_constant()
> 433:   }
> 434: }

This should be a function in ConstantPool::print()

src/hotspot/share/interpreter/bytecodeTracer.cpp line 462:

> 460:     }
> 461:   }
> 462: }

Line 444-461 should call a function in cpCache like:
void ConstantPoolCacheEntry::print(outputStream* st, int index) const {

If this doesn't have the format you want, you can enhance this function.

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PR: https://git.openjdk.org/jdk/pull/9957