Handle null names in JVM extractor

Updated JvmExtractor.cs to safely handle cases where class, method, or field names may be null by providing default values. Added new dbscheme files and scripts for JVM binary extraction, and updated the binary dbscheme to support new extraction features.

Author: gfs

binary/extractor/jvm/Semmle.Extraction.Java.ByteCode/JvmExtractor.cs

@@ -88,7 +88,7 @@ private void ExtractClass(ClassFile classFile, string sourcePath)
 
         // Get class name from constant pool - ClassConstant now has Name directly resolved
         var thisClassConstant = classFile.Constants.Get(classFile.This);
-        var className = thisClassConstant.Name;
+        var className = thisClassConstant.Name ?? "UnknownClass";
 
         // Extract type (class/interface/enum)
         var typeId = trap.GetId();
@@ -307,7 +307,7 @@ private void ExtractCode(IKVM.ByteCode.Decoding.Attribute attr, int methodId, Cl
             if (!handler.CatchType.IsNil)
             {
                 var catchClassConst = classFile.Constants.Get(handler.CatchType);
-                catchType = catchClassConst.Name.Replace('/', '.');
+                catchType = catchClassConst.Name?.Replace('/', '.') ?? "";
             }
 
             trap.WriteTuple("jvm_exception_handler", handlerId, methodId, 
@@ -584,9 +584,9 @@ private void ExtractFieldRef(Instruction instr, int instrId, ClassFile classFile
             var fieldRef = classFile.Constants.Get(new FieldrefConstantHandle(handle.Slot));
 
             trap.WriteTuple("jvm_field_operand", instrId, 
-                fieldRef.ClassName.Replace('/', '.'),
-                fieldRef.Name,
-                fieldRef.Descriptor);
+                fieldRef.ClassName?.Replace('/', '.') ?? "",
+                fieldRef.Name ?? "",
+                fieldRef.Descriptor ?? "");
         }
         catch
         {
@@ -607,33 +607,33 @@ private void ExtractMethodRef(Instruction instr, int instrId, ClassFile classFil
                 case OpCode.InvokeVirtual:
                     var virtHandle = instr.AsInvokeVirtual().Method;
                     var virtRef = classFile.Constants.Get(new MethodrefConstantHandle(virtHandle.Slot));
-                    className = virtRef.ClassName.Replace('/', '.');
-                    methodName = virtRef.Name;
-                    descriptor = virtRef.Descriptor;
+                    className = virtRef.ClassName?.Replace('/', '.') ?? "";
+                    methodName = virtRef.Name ?? "";
+                    descriptor = virtRef.Descriptor ?? "";
                     break;
 
                 case OpCode.InvokeSpecial:
                     var specHandle = instr.AsInvokeSpecial().Method;
                     var specRef = classFile.Constants.Get(new MethodrefConstantHandle(specHandle.Slot));
-                    className = specRef.ClassName.Replace('/', '.');
-                    methodName = specRef.Name;
-                    descriptor = specRef.Descriptor;
+                    className = specRef.ClassName?.Replace('/', '.') ?? "";
+                    methodName = specRef.Name ?? "";
+                    descriptor = specRef.Descriptor ?? "";
                     break;
 
                 case OpCode.InvokeStatic:
                     var statHandle = instr.AsInvokeStatic().Method;
                     var statRef = classFile.Constants.Get(new MethodrefConstantHandle(statHandle.Slot));
-                    className = statRef.ClassName.Replace('/', '.');
-                    methodName = statRef.Name;
-                    descriptor = statRef.Descriptor;
+                    className = statRef.ClassName?.Replace('/', '.') ?? "";
+                    methodName = statRef.Name ?? "";
+                    descriptor = statRef.Descriptor ?? "";
                     break;
 
                 case OpCode.InvokeInterface:
                     var intfHandle = instr.AsInvokeInterface().Method;
                     var intfRef = classFile.Constants.Get(new InterfaceMethodrefConstantHandle(intfHandle.Slot));
-                    className = intfRef.ClassName.Replace('/', '.');
-                    methodName = intfRef.Name;
-                    descriptor = intfRef.Descriptor;
+                    className = intfRef.ClassName?.Replace('/', '.') ?? "";
+                    methodName = intfRef.Name ?? "";
+                    descriptor = intfRef.Descriptor ?? "";
                     break;
             }
 
@@ -662,7 +662,7 @@ private void ExtractTypeRef(ConstantHandle constHandle, int instrId, ClassFile c
                 return;
 
             var classConst = classFile.Constants.Get(new ClassConstantHandle(constHandle.Slot));
-            trap.WriteTuple("jvm_type_operand", instrId, classConst.Name.Replace('/', '.'));
+            trap.WriteTuple("jvm_type_operand", instrId, classConst.Name?.Replace('/', '.') ?? "");
         }
         catch
         {