From 9a37dc0ce64c51fd57f5e658a5af8f3671a26b0a Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Thu, 25 Jul 2019 13:55:29 -0300
Subject: Small corrections when setting 'L->top'

- OP_NEWTABLE can use 'ra + 1' to set top (instead of ci->top);
- OP_CLOSE doesn't need to set top ('Protect' already does that);
- OP_TFORCALL must use 'ProtectNT', to preserve the top already set.
  (That was a small bug, because iterators could be called with
   extra parameters besides the state and the control variable.)
- Comments and an extra test for the bug in previous item.
---
 lvm.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

(limited to 'lvm.c')

diff --git a/lvm.c b/lvm.c
index d9bd0ab3..26477c2c 100644
--- a/lvm.c
+++ b/lvm.c
@@ -1258,7 +1258,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         if (TESTARG_k(i))
           c += GETARG_Ax(*pc) * (MAXARG_C + 1);
         pc++;  /* skip extra argument */
-        L->top = ci->top;  /* correct top in case of GC */
+        L->top = ra + 1;  /* correct top in case of emergency GC */
         t = luaH_new(L);  /* memory allocation */
         sethvalue2s(L, ra, t);
         if (b != 0 || c != 0)
@@ -1478,7 +1478,6 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_CLOSE) {
-        L->top = ra + 1;  /* everything is free after this slot */
         Protect(luaF_close(L, ra, LUA_OK));
         vmbreak;
       }
@@ -1755,7 +1754,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         /* push function, state, and control variable */
         memcpy(ra + 4, ra, 3 * sizeof(*ra));
         L->top = ra + 4 + 3;
-        Protect(luaD_call(L, ra + 4, GETARG_C(i)));  /* do the call */
+        ProtectNT(luaD_call(L, ra + 4, GETARG_C(i)));  /* do the call */
         updatestack(ci);  /* stack may have changed */
         i = *(pc++);  /* go to next instruction */
         lua_assert(GET_OPCODE(i) == OP_TFORLOOP && ra == RA(i));
@@ -1776,7 +1775,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         if (n == 0)
           n = cast_int(L->top - ra) - 1;  /* get up to the top */
         else
-          L->top = ci->top;  /* correct top in case of GC */
+          L->top = ci->top;  /* correct top in case of emergency GC */
         last += n;
         if (TESTARG_k(i)) {
           last += GETARG_Ax(*pc) * (MAXARG_C + 1);
-- 
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