commit 9e6807c3c9d5036e999f636f936df07b72284442
author Roberto Ierusalimschy <roberto@inf.puc-rio.br> Mon Jul 22 09:41:10 2019 -0300
committer Roberto Ierusalimschy <roberto@inf.puc-rio.br> Mon Jul 22 09:41:10 2019 -0300
tree 39100fb44792114905f00d1b638212f620d12a25
parent 2f22c6bb79d209a55b3fc8e0b2d9c9f89f038174

Do not collect open upvalues

Open upvalues are kept alive together with their corresponding
stack. This change makes a simpler and safer fix to the issue in
commit 440a5ee78c8, about upvalues in the list of open upvalues
being collected while others are being created. (That previous fix
may not be correct.)

lfunc.c

diff --git a/lfunc.c b/lfunc.c
index f7edf56..6f2f897 100644
--- a/lfunc.c
+++ b/lfunc.c
@@ -83,21 +83,20 @@
 
 /*
 ** Find and reuse, or create if it does not exist, an upvalue
-** at the given level and set it to the given slot.
+** at the given level.
 */
-void luaF_setupval (lua_State *L, StkId level, UpVal **slot) {
+UpVal *luaF_findupval (lua_State *L, StkId level) {
   UpVal **pp = &L->openupval;
   UpVal *p;
   lua_assert(isintwups(L) || L->openupval == NULL);
   while ((p = *pp) != NULL && uplevel(p) >= level) {  /* search for it */
-    *slot = p;
-    if (uplevel(p) == level && !isdead(G(L), p))  /* corresponding upvalue? */
-      return;  /* found it */
+    lua_assert(!isdead(G(L), p));
+    if (uplevel(p) == level)  /* corresponding upvalue? */
+      return p;  /* return it */
     pp = &p->u.open.next;
   }
-  /* not found: create a new upvalue after 'pp' (which is
-    anchored in 'slot', in case of an emergency collection) */
-  *slot = newupval(L, 0, level, pp);
+  /* not found: create a new upvalue after 'pp' */
+  return newupval(L, 0, level, pp);
 }
 
 

lfunc.h

diff --git a/lfunc.h b/lfunc.h
index 72fc913..0ed79c4 100644
--- a/lfunc.h
+++ b/lfunc.h
@@ -57,7 +57,7 @@
 LUAI_FUNC CClosure *luaF_newCclosure (lua_State *L, int nelems);
 LUAI_FUNC LClosure *luaF_newLclosure (lua_State *L, int nelems);
 LUAI_FUNC void luaF_initupvals (lua_State *L, LClosure *cl);
-LUAI_FUNC void luaF_setupval (lua_State *L, StkId level, UpVal **slot);
+LUAI_FUNC UpVal *luaF_findupval (lua_State *L, StkId level);
 LUAI_FUNC void luaF_newtbcupval (lua_State *L, StkId level);
 LUAI_FUNC int luaF_close (lua_State *L, StkId level, int status);
 LUAI_FUNC void luaF_unlinkupval (UpVal *uv);

lgc.c

diff --git a/lgc.c b/lgc.c
index c5babfe..b7220cf 100644
--- a/lgc.c
+++ b/lgc.c
@@ -569,10 +569,8 @@
              th->openupval == NULL || isintwups(th));
   for (; o < th->top; o++)  /* mark live elements in the stack */
     markvalue(g, s2v(o));
-  for (uv = th->openupval; uv != NULL; uv = uv->u.open.next) {
-    if (uv->tbc)  /* to be closed? */
-      markobject(g, uv);  /* cannot be collected */
-  }
+  for (uv = th->openupval; uv != NULL; uv = uv->u.open.next)
+    markobject(g, uv);  /* open upvalues cannot be collected */
   if (g->gcstate == GCSatomic) {  /* final traversal? */
     StkId lim = th->stack + th->stacksize;  /* real end of stack */
     for (; o < lim; o++)  /* clear not-marked stack slice */

lvm.c

diff --git a/lvm.c b/lvm.c
index d3e0519..d9bd0ab 100644
--- a/lvm.c
+++ b/lvm.c
@@ -697,7 +697,7 @@
   setclLvalue2s(L, ra, ncl);  /* anchor new closure in stack */
   for (i = 0; i < nup; i++) {  /* fill in its upvalues */
     if (uv[i].instack)  /* upvalue refers to local variable? */
-      luaF_setupval(L, base + uv[i].idx, &ncl->upvals[i]);
+      ncl->upvals[i] = luaF_findupval(L, base + uv[i].idx);
     else  /* get upvalue from enclosing function */
       ncl->upvals[i] = encup[uv[i].idx];
     luaC_objbarrier(L, ncl, ncl->upvals[i]);