From 28d829c86712ce5bc453feccc5129a32f78d80c0 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Tue, 4 Dec 2018 15:01:42 -0200
Subject: Calls cannot be tail in the scope of a to-be-closed variable

A to-be-closed variable must be closed when a block ends, so even
a 'return foo()' cannot directly returns the results of 'foo'; the
function must close the scope before returning.
---
 lparser.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'lparser.c')

diff --git a/lparser.c b/lparser.c
index e525e578..eed8bffd 100644
--- a/lparser.c
+++ b/lparser.c
@@ -53,6 +53,7 @@ typedef struct BlockCnt {
   lu_byte nactvar;  /* # active locals outside the block */
   lu_byte upval;  /* true if some variable in the block is an upvalue */
   lu_byte isloop;  /* true if 'block' is a loop */
+  lu_byte insidetbc;  /* true if inside the scope of a to-be-closed var. */
 } BlockCnt;
 
 
@@ -510,6 +511,7 @@ static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isloop) {
   bl->firstlabel = fs->ls->dyd->label.n;
   bl->firstgoto = fs->ls->dyd->gt.n;
   bl->upval = 0;
+  bl->insidetbc = (fs->bl != NULL && fs->bl->insidetbc);
   bl->previous = fs->bl;
   fs->bl = bl;
   lua_assert(fs->freereg == fs->nactvar);
@@ -1631,6 +1633,7 @@ static void tocloselocalstat (LexState *ls) {
   checknext(ls, '=');
   exp1(ls, 0);
   markupval(fs, fs->nactvar);
+  fs->bl->insidetbc = 1;  /* in the scope of a to-be-closed variable */
   adjustlocalvars(ls, 1);
   luaK_codeABC(fs, OP_TBC, fs->nactvar - 1, 0, 0);
 }
@@ -1701,7 +1704,7 @@ static void retstat (LexState *ls) {
     nret = explist(ls, &e);  /* optional return values */
     if (hasmultret(e.k)) {
       luaK_setmultret(fs, &e);
-      if (e.k == VCALL && nret == 1) {  /* tail call? */
+      if (e.k == VCALL && nret == 1 && !fs->bl->insidetbc) {  /* tail call? */
         SET_OPCODE(getinstruction(fs,&e), OP_TAILCALL);
         lua_assert(GETARG_A(getinstruction(fs,&e)) == fs->nactvar);
       }
-- 
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