JACOBIN-398 While tracing, FormatField returning "<ERROR..." --> DumpObject(title=why?/what?, indentation=0)

[texadactyl]

While tracing, if there are field formatting errors for any reason, we will now dump the entire object.

Error conditions diagnosed in FormatField:

• <ERROR nil class pointer!>
• <ERROR FieldTable["value"] not found!> when FieldTable is nonempty

Error conditions diagnosed in fmtHelper (called by FormatField):

• <ERROR Ftype=bool but unexpected Fvalue variable type: observed-type !>
• <ERROR nil Fvalue!> E.g. Ftype is [B but the byte array pointer is nil

An object dump will always attempt to depict both the FieldTable contents and the Fields slice contents.
See the object/object_test.go unit testing.

E.g. Dump an object with a non-empty FieldTable but an empty Fields slice:

   DumpObject java/lang/madeUpClass {
   	Class: java/lang/madeUpClass
   	Field Table:
   		Fld myChar: (C) 'C'
   		Fld myFloat: (F) 1.000000
   		Fld myLong: (J) 42
   		Fld myByte: (B) 61
   		Fld myStaticTrue: (XZ) true
   		Fld myString: (Ljava/lang/String;) Hello, Unka Andoo !
   		Fld myDouble: (D) 2.000000
   		Fld myInt: (I) 42
   		Fld myShort: (S) 42
   		Fld myFalse: (Z) false
   	Field Slice is <empty>
   }

E.g. Dump an object with a non-empty Fields slice but an empty FieldTable:

DumpObject [B string] {
	Class: java/lang/madeUpClass
	Field Table is <empty>
	Field Slice (11):
		Fld ([B) 54 68 69 73 20 69 73 20 61 20 63 6f 6d 70 61 63 74 20 73 74 72 69 6e 67 20 66 72 6f 6d 20 61 20 47 6f 20 73 74 72 69 6e 67
		Fld (B) 00
		Fld (I) 0
		Fld (XZ) true
		Fld (L) <nil>
		Fld (L) <nil>
		Fld (L) <nil>
		Fld (L) <nil>
		Fld (L) <nil>
		Fld (Z) false
		Fld (L) <nil>
}

E.g. Currently, jacotest case "zippy" exhibits an object with both field structures being non-empty but missing the "value" field in the FieldTable. This error is caught in FormatField:

DumpObject <ERROR FieldTable["value"] not found!> {
	Class: java/io/File
	Field Table:
		Fld serialVersionUID: (XJ) 0
		Fld PREFIX_LENGTH_OFFSET: (XJ) 0
		Fld fs: (XLjava/io/FileSystem;) <nil>
		Fld pathSeparatorChar: (XC) '\x00'
		Fld pathSeparator: (XLjava/lang/String;) <nil>
		Fld UNSAFE: (XLjdk/internal/misc/Unsafe;) <nil>
		Fld filePath: (Ljava/nio/file/Path;) <nil>
		Fld prefixLength: (I) 0
		Fld status: (Ljava/io/File$PathStatus;) <nil>
		Fld separatorChar: (XC) '\x00'
		Fld separator: (XLjava/lang/String;) <nil>
		Fld PATH_OFFSET: (XJ) 0
		Fld $assertionsDisabled: (XZ) false
		Fld path: (Ljava/lang/String;) <nil>
	Field Slice (14):
		Fld (XLjava/io/FileSystem;) <nil>
		Fld (Ljava/lang/String;) <nil>
		Fld (Ljava/io/File$PathStatus;) <nil>
		Fld (I) 0
		Fld (XC) '\x00'
		Fld (XLjava/lang/String;) <nil>
		Fld (XC) '\x00'
		Fld (XLjava/lang/String;) <nil>
		Fld (XLjdk/internal/misc/Unsafe;) <nil>
		Fld (XJ) 0
		Fld (XJ) 0
		Fld (XJ) 0
		Fld (Ljava/nio/file/Path;) <nil>
		Fld (XZ) false
}

[texadactyl]

@platypusguy - This is a bit off topic from the PR.

Note Fld pathSeparator: (XLjava/lang/String;) <nil> above. Shouldn't the Fvalue be "/" or "\"? Maybe I am confused.

It appears that when field type is XL (static reference) or L (non-static reference), in both FieldTable and the Fields slice,

• Ftype <- field type concatenated with the field value
• Fvalue <- nil

Is that correctly done in jvm/instantiate.go function createField?
Questions:

• Ftype is "L" or "XL" and the Fvalue is "Lreference-name;"?
• Ftype is correct as-is but Fvalue should be non-nil e.g. the string bytes?
• Something else that is not intuitively obvious to me?

I get that byte arrays are initialized empty. My questions are about types.Ref.