From 62bac1d612a83e9a1823e761dfd16b5cef991e25 Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Tue, 30 May 2017 18:09:51 +0300
Subject: [PATCH] Added check for nullptr to CLSS and META instructions of
 scripting VM

https://forum.zdoom.org/viewtopic.php?t=56667
---
 src/scripting/vm/vmexec.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/scripting/vm/vmexec.h b/src/scripting/vm/vmexec.h
index 7e8a53a6a..d5b8ba6b1 100644
--- a/src/scripting/vm/vmexec.h
+++ b/src/scripting/vm/vmexec.h
@@ -37,6 +37,16 @@
 #error vmexec.h must not be #included outside vmexec.cpp. Use vm.h instead.
 #endif
 
+static PClass* GetClass(void* ptr)
+{
+	if (nullptr == ptr)
+	{
+		ThrowAbortException(X_READ_NIL, nullptr);
+	}
+
+	return static_cast<DObject*>(ptr)->GetClass();
+}
+
 static int Exec(VMFrameStack *stack, const VMOP *pc, VMReturn *ret, int numret)
 {
 #if COMPGOTO
@@ -140,12 +150,12 @@ static int Exec(VMFrameStack *stack, const VMOP *pc, VMReturn *ret, int numret)
 
 	OP(CLSS):
 		ASSERTA(a); ASSERTA(B);
-		reg.a[a] = ((DObject*)reg.a[B])->GetClass();	// I wish this could be done without a special opcode but there's really no good way to guarantee initialization of the Class pointer...
+		reg.a[a] = GetClass(reg.a[B]);
 		NEXTOP;
 
 	OP(META):
 		ASSERTA(a); ASSERTA(B);
-		reg.a[a] = ((DObject*)reg.a[B])->GetClass()->Meta;	// I wish this could be done without a special opcode but there's really no good way to guarantee initialization of the Class pointer...
+		reg.a[a] = GetClass(reg.a[B])->Meta;
 		NEXTOP;
 
 	OP(LB):