Limit State.Top >= 0

zombiezen · zombiezen · commit b29b64467fe3 · 2024-12-09T11:23:54.000-08:00
Probably not an issue in practice,
but want to be safe for strange stacks.
diff --git a/internal/mylua/lua.go b/internal/mylua/lua.go
@@ -193,7 +193,7 @@ func (l *State) Top() int {
 	if len(l.callStack) == 0 {
 		return 0
 	}
-	return len(l.stack) - l.frame().registerStart()
+	return max(len(l.stack)-l.frame().registerStart(), 0)
 }
 
 // SetTop accepts any index, or 0, and sets the stack top to this index.

Original file line number	Diff line number	Diff line change
`@@ -193,7 +193,7 @@ func (l *State) Top() int {`
`193`	`193`	`if len(l.callStack) == 0 {`
`194`	`194`	`return 0`
`195`	`195`	`}`
`196`		`- return len(l.stack) - l.frame().registerStart()`
	`196`	`+ return max(len(l.stack)-l.frame().registerStart(), 0)`
`197`	`197`	`}`
`198`	`198`
`199`	`199`	`// SetTop accepts any index, or 0, and sets the stack top to this index.`