From 0e53a314d7910898e1ea5ba90385d43e8a6c5e57 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Sat, 29 May 2021 15:31:13 +0200
Subject: [PATCH] Fix use-def analysis for vararg functions.

Reported by Shmuel Zeigerman.
---
 src/lj_snap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/lj_snap.c b/src/lj_snap.c
index 0c5e8e90..eb14058e 100644
--- a/src/lj_snap.c
+++ b/src/lj_snap.c
@@ -271,8 +271,10 @@ static BCReg snap_usedef(jit_State *J, uint8_t *udf,
 void lj_snap_purge(jit_State *J)
 {
   uint8_t udf[SNAP_USEDEF_SLOTS];
-  BCReg maxslot = J->maxslot;
-  BCReg s = snap_usedef(J, udf, J->pc, maxslot);
+  BCReg s, maxslot = J->maxslot;
+  if (bc_op(*J->pc) == BC_FUNCV && maxslot > J->pt->numparams)
+    maxslot = J->pt->numparams;
+  s = snap_usedef(J, udf, J->pc, maxslot);
   for (; s < maxslot; s++)
     if (udf[s] != 0)
       J->base[s] = 0;  /* Purge dead slots. */