Add final modifiers on those handlers fields

Also added an optional asm transformer to catch potential problems

src/main/java/codechicken/nei/asm/GuiContainerManagerAPITransformer.java

@@ -0,0 +1,38 @@
+package codechicken.nei.asm;
+
+import codechicken.lib.asm.ASMHelper;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.MethodVisitor;
+
+import static org.objectweb.asm.Opcodes.POP;
+import static org.objectweb.asm.Opcodes.PUTSTATIC;
+
+public class GuiContainerManagerAPITransformer extends ClassVisitor {
+    private final String tname;
+    private boolean changed = false;
+
+    public GuiContainerManagerAPITransformer(int api, ClassVisitor cv, String tname) {
+        super(api, cv);
+        this.tname = tname;
+    }
+
+    @Override
+    public MethodVisitor visitMethod(int access, String mname, String mdesc, String signature, String[] exceptions) {
+        return new MethodVisitor(api, super.visitMethod(access, mname, mdesc, signature, exceptions)) {
+            @Override
+            public void visitFieldInsn(int opcode, String owner, String name, String desc) {
+                if (opcode == PUTSTATIC && "codechicken/nei/guihook/GuiContainerManager".equals(owner) && name.endsWith("Handlers") && desc.equals("Ljava/util/LinkedList;")) {
+                    ASMHelper.logger.warn("Found suspicious PUTSTATIC {} in {}#{}{}, replacing with POP!", name, tname, mname, mdesc);
+                    changed = true;
+                    super.visitInsn(POP);
+                } else {
+                    super.visitFieldInsn(opcode, owner, name, desc);
+                }
+            }
+        };
+    }
+
+    public boolean isChanged() {
+        return changed;
+    }
+}

src/main/java/codechicken/nei/asm/NEITransformer.java

@@ -41,6 +41,7 @@ public class NEITransformer implements IClassTransformer
         ASMInit.init();
     }
 
+    private final boolean paranoidMode = Boolean.getBoolean("nei.paranoid");
     private final ModularASMTransformer transformer = new ModularASMTransformer();
     private final Map<String, ASMBlock> asmblocks = ASMReader.loadResource("/assets/nei/asm/blocks.asm");
 
@@ -264,6 +265,14 @@ public class NEITransformer implements IClassTransformer
                 }
                 bytes = transformSubclasses(name, bytes);
             }
+            if (paranoidMode && !tname.startsWith("codechicken.nei")) {
+                ClassReader cr = new ClassReader(bytes);
+                ClassWriter cw = new ClassWriter(0);
+                GuiContainerManagerAPITransformer cv = new GuiContainerManagerAPITransformer(ASM5, cw, tname);
+                cr.accept(cv, ClassReader.SKIP_DEBUG);
+                if (cv.isChanged())
+                    bytes = cw.toByteArray();
+            }
 
             bytes = transformer.transform(name, bytes);
         } catch (Exception e) {

src/main/java/codechicken/nei/guihook/GuiContainerManager.java

@@ -36,11 +36,11 @@ public class GuiContainerManager
     public GuiContainer window;
 
     public static RenderItem drawItems = new RenderItem();
-    public static LinkedList<IContainerTooltipHandler> tooltipHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
-    public static LinkedList<IContainerInputHandler> inputHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
-    public static LinkedList<IContainerDrawHandler> drawHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
-    public static LinkedList<IContainerObjectHandler> objectHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
-    public static LinkedList<IContainerSlotClickHandler> slotClickHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
+    public static final LinkedList<IContainerTooltipHandler> tooltipHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
+    public static final LinkedList<IContainerInputHandler> inputHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
+    public static final LinkedList<IContainerDrawHandler> drawHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
+    public static final LinkedList<IContainerObjectHandler> objectHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
+    public static final LinkedList<IContainerSlotClickHandler> slotClickHandlers = new HideousLinkedList<>(new CopyOnWriteArrayList<>());
 
     static {
         addSlotClickHandler(new DefaultSlotClickHandler());