From 439d3c75ab6cd6f9408526f35e233a1755bcf66c Mon Sep 17 00:00:00 2001
From: samisalreadytaken <46823719+samisalreadytaken@users.noreply.github.com>
Date: Thu, 27 Jan 2022 00:22:00 +0300
Subject: [PATCH] Fix VM stack corruption

---
 sp/src/vscript/vscript_squirrel.cpp | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/sp/src/vscript/vscript_squirrel.cpp b/sp/src/vscript/vscript_squirrel.cpp
index 101a5252..b8465419 100644
--- a/sp/src/vscript/vscript_squirrel.cpp
+++ b/sp/src/vscript/vscript_squirrel.cpp
@@ -1699,7 +1699,9 @@ struct SquirrelSafeCheck
 
 	~SquirrelSafeCheck()
 	{
-		if (top_ != (sq_gettop(vm_) - outputCount_))
+		SQInteger curtop = sq_gettop(vm_);
+		SQInteger diff = curtop - outputCount_;
+		if ( top_ != diff )
 		{
 			Assert(!"Squirrel VM stack is not consistent");
 			Error("Squirrel VM stack is not consistent\n");
@@ -2352,6 +2354,8 @@ bool SquirrelVM::ScopeIsHooked( HSCRIPT hScope, const char *pszEventName )
 	if (!hScope)
 		return true;
 
+	SquirrelSafeCheck safeCheck(vm_);
+
 	Assert(hScope != INVALID_HSCRIPT);
 
 	sq_pushroottable(vm_);
@@ -2371,7 +2375,7 @@ bool SquirrelVM::ScopeIsHooked( HSCRIPT hScope, const char *pszEventName )
 		return false;
 	}
 
-	sq_pop(vm_, 3);
+	sq_pop(vm_, 4);
 	return val ? true : false;
 }
 
@@ -2391,6 +2395,8 @@ HSCRIPT SquirrelVM::LookupHookFunction(const char *pszEventName, HSCRIPT hScope,
 	if (!ScopeIsHooked(hScope, pszEventName))
 		return nullptr;
 
+	SquirrelSafeCheck safeCheck(vm_);
+
 	sq_pushroottable(vm_);
 	sq_pushstring(vm_, "Hooks", -1);
 	sq_get(vm_, -2);
@@ -2401,7 +2407,7 @@ HSCRIPT SquirrelVM::LookupHookFunction(const char *pszEventName, HSCRIPT hScope,
 	sq_resetobject(&obj);
 	sq_getstackobj(vm_, -1, &obj);
 	sq_addref(vm_, &obj);
-	sq_pop(vm_, 2);
+	sq_pop(vm_, 3);
 
 	HSQOBJECT* pObj = new HSQOBJECT;
 	*pObj = obj;