RFR: 8292699: Improve printing of classes in native debugger

[Ioi Lam]

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.

(In future RFEs, I plan to add more detailed printing, such as the constant pool cache entry of resolved bootstrap methods).

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

-------------

Commit messages:
 - 8292699: Improve printing of classes in native debugger

Changes: https://git.openjdk.org/jdk/pull/9957/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9957&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292699
  Stats: 346 lines in 11 files changed: 258 ins; 61 del; 27 mod
  Patch: https://git.openjdk.org/jdk/pull/9957.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9957/head:pull/9957

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