Properly handle unreachable instructions and null stack entries (#574)

* Properly handle unreachable instructions and null stack entries

* ASM can be trusted

Co-authored-by: Joseph Burton <burtonjae@hotmail.co.uk>

---------

Co-authored-by: Joseph Burton <burtonjae@hotmail.co.uk>

1 files changed, 5 insertions, 1 deletions

diff --git a/enigma/src/main/java/cuchaz/enigma/analysis/index/IndexReferenceVisitor.java b/enigma/src/main/java/cuchaz/enigma/analysis/index/IndexReferenceVisitor.java
index ecd460d..698a351 100644
--- a/enigma/src/main/java/cuchaz/enigma/analysis/index/IndexReferenceVisitor.java
+++ b/enigma/src/main/java/cuchaz/enigma/analysis/index/IndexReferenceVisitor.java
@@ -139,13 +139,17 @@ public class IndexReferenceVisitor extends ClassVisitor {
                 }
 
                 private ReferenceTargetType getReferenceTargetType(int stackDepth) {
+                        if (stack == null) { // Unreachable instruction
+                                return ReferenceTargetType.uninitialized();
+                        }
+
                         if (stackDepth >= stack.size()) {
                                 throw new IllegalStateException("Stack depth " + stackDepth + " is higher than the stack: " + stackValuesToString(stack) + " in method " + callerEntry);
                         }
 
                         Object stackValue = stack.get(stack.size() - 1 - stackDepth);
 
-                        if (stackValue.equals(Opcodes.UNINITIALIZED_THIS) || stackValue instanceof Label) {
+                        if (stackValue.equals(Opcodes.UNINITIALIZED_THIS) || stackValue.equals(Opcodes.NULL) || stackValue instanceof Label) {
                                 return ReferenceTargetType.uninitialized();
                         }