JACOBIN-886 Added tests for the new java/lang/Class handling

Author: platypusguy

src/classloader/jlc_test.go

@@ -0,0 +1,165 @@
+/*
+ * Jacobin VM - A Java virtual machine
+ * Copyright (c) 2026 by the Jacobin Authors. All rights reserved.
+ * Licensed under Mozilla Public License 2.0 (MPL 2.0)  Consult jacobin.org.
+ */
+
+package classloader
+
+import (
+	"jacobin/src/globals"
+	"jacobin/src/object"
+	"jacobin/src/stringPool"
+	"jacobin/src/trace"
+	"testing"
+)
+
+func TestMakeJlcObject(t *testing.T) {
+	globals.InitGlobals("test")
+	trace.Init()
+
+	className := "java/lang/String"
+	jlcObj := MakeJlcObject(className)
+
+	if jlcObj == nil {
+		t.Fatal("MakeJlcObject returned nil")
+	}
+
+	// Verify the KlassName of the returned object is java/lang/Class
+	// (StringPoolJavaLangClassIndex is used in MakeJlcObject)
+	classNameStrPtr := stringPool.GetStringPointer(jlcObj.KlassName)
+	if classNameStrPtr == nil || *classNameStrPtr != "java/lang/Class" {
+		t.Errorf("Expected KlassName to point to 'java/lang/Class', got '%v'",
+			*classNameStrPtr)
+	}
+
+	// Verify the "name" field contains a String object with the correct class name
+	jlcObj.ThMutex.RLock()
+	nameField, ok := jlcObj.FieldTable["name"]
+	jlcObj.ThMutex.RUnlock()
+
+	if !ok {
+		t.Fatal("Jlc object missing 'name' field")
+	}
+
+	nameObj, ok := nameField.Fvalue.(*object.Object)
+	if !ok {
+		t.Fatalf("Jlc object 'name' field is not an *object.Object, got %T", nameField.Fvalue)
+	}
+
+	actualName := object.GoStringFromStringObject(nameObj)
+	if actualName != className {
+		t.Errorf("Expected Jlc name to be '%s', got '%s'", className, actualName)
+	}
+
+	// Verify $statics field is an empty string slice
+	jlcObj.ThMutex.RLock()
+	staticsField, ok := jlcObj.FieldTable["$statics"]
+	jlcObj.ThMutex.RUnlock()
+
+	if !ok {
+		t.Fatal("Jlc object missing '$statics' field")
+	}
+
+	staticsSlice, ok := staticsField.Fvalue.([]string)
+	if !ok {
+		t.Fatalf("Jlc object '$statics' field is not a []string, got %T", staticsField.Fvalue)
+	}
+
+	if len(staticsSlice) != 0 {
+		t.Errorf("Expected empty '$statics' slice, got length %d", len(staticsSlice))
+	}
+}
+
+// Test that the String class is loaded and initialized correctly
+// and that the java/lang/Class instance in the loaded class is correct
+func TestStringClassStaticsLoaded(t *testing.T) {
+	// Full initialization required to load base classes and string pool
+	globals.InitGlobals("test")
+	trace.Init()
+	Init() // This calls InitMethodArea, JmodMapInit, GetBaseJmodBytes
+
+	// Load the base classes which includes java.lang.String
+	LoadBaseClasses()
+
+	className := "java/lang/String"
+
+	// Fetch the class from the Method Area
+	k := MethAreaFetch(className)
+	if k == nil {
+		t.Fatalf("Class %s not found in MethArea after LoadBaseClasses", className)
+	}
+
+	// Retrieve the ClassObject (the JLC instance) from the class data
+	classObj := k.Data.ClassObject
+	if classObj == nil {
+		t.Fatalf("ClassObject for %s is nil", className)
+	}
+
+	// Verify the "name" field contains a String object with the correct class name
+	classObj.ThMutex.RLock()
+	nameField, ok := classObj.FieldTable["name"]
+	classObj.ThMutex.RUnlock()
+
+	if !ok {
+		t.Fatal("Class object missing 'name' field")
+	}
+
+	// Note: in convertToPostableClass, the 'name' field is set as a String object
+	nameObj, ok := nameField.Fvalue.(*object.Object)
+	if !ok {
+		t.Fatalf("Class object 'name' field is not an *object.Object, got %T", nameField.Fvalue)
+	}
+
+	actualName := object.GoStringFromStringObject(nameObj)
+	if actualName != className {
+		t.Errorf("Expected Class object name to be '%s', got '%s'", className, actualName)
+	}
+
+	// Verify that the $statics slice contains expected static fields from java.lang.String
+	// serialVersionUID is universally present in Serializable classes like String.
+	expectedStatic := "serialVersionUIDJ" // Name + Descriptor
+
+	classObj.ThMutex.RLock()
+	staticsField, ok := classObj.FieldTable["$statics"]
+	classObj.ThMutex.RUnlock()
+
+	if !ok {
+		t.Fatal("Class object missing '$statics' field")
+	}
+
+	staticsSlice, ok := staticsField.Fvalue.([]string)
+	if !ok {
+		t.Fatalf("Class object '$statics' field is not a []string, got %T", staticsField.Fvalue)
+	}
+
+	found := false
+	for _, s := range staticsSlice {
+		if s == expectedStatic {
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		t.Errorf("Expected static field '%s' not found in java.lang.String $statics array", expectedStatic)
+	}
+
+	// Verify the $klass pointer points back to the metadata
+	classObj.ThMutex.RLock()
+	klassField, ok := classObj.FieldTable["$klass"]
+	classObj.ThMutex.RUnlock()
+
+	if !ok {
+		t.Fatal("Class object missing '$klass' field")
+	}
+
+	klassDataPtr, ok := klassField.Fvalue.(*ClData)
+	if !ok {
+		t.Fatalf("Class object '$klass' field is not a *ClData, got %T", klassField.Fvalue)
+	}
+
+	if klassDataPtr.Name != className {
+		t.Errorf("Expected $klass pointer to point to ClData for '%s', got '%s'", className, klassDataPtr.Name)
+	}
+}