src/: Upvalues are now just TValues (possibly referencing on-stack)

  - Removes `Upval` class
  - closing over upvalues is now done by creating new on-stack TValue objects
  - No more `openupval` linked list

With this fix, upvalues from collected coroutines will no longer keep other values alive

Closes #44

6 files changed, 20 insertions, 82 deletions

diff --git a/src/lapi.js b/src/lapi.js
index ec643b3..8ed67f5 100644
--- a/src/lapi.js
+++ b/src/lapi.js
@@ -32,10 +32,7 @@ const {
     from_userstring,
     to_luastring,
 } = require('./defs.js');
-const {
-    api_check,
-    lua_assert
-} = require('./llimits.js');
+const { api_check } = require('./llimits.js');
 const ldebug    = require('./ldebug.js');
 const ldo       = require('./ldo.js');
 const { luaU_dump } = require('./ldump.js');
@@ -555,7 +552,7 @@ const aux_upvalue = function(L, fi, n) {
             let name = p.upvalues[n-1].name;
             return {
                 name: name ? name.getstr() : to_luastring("(*no name)", true),
-                val: f.upvals[n-1].v
+                val: f.upvals[n-1]
             };
         }
         default: return null;  /* not a closure */
@@ -930,7 +927,7 @@ const lua_load = function(L, reader, data, chunkname, mode) {
             /* get global table from registry */
             let gt = ltable.luaH_getint(L.l_G.l_registry.value, LUA_RIDX_GLOBALS);
             /* set global table as 1st upvalue of 'f' (may be LUA_ENV) */
-            f.upvals[0].v.setfrom(gt);
+            f.upvals[0].setfrom(gt);
         }
     }
     return status;
@@ -1111,13 +1108,9 @@ const lua_upvalueid = function(L, fidx, n) {
 const lua_upvaluejoin = function(L, fidx1, n1, fidx2, n2) {
     let ref1 = getupvalref(L, fidx1, n1);
     let ref2 = getupvalref(L, fidx2, n2);
-    let up1 = ref1.upval;
     let up2 = ref2.upval;
     let f1 = ref1.closure;
-    lua_assert(up1.refcount > 0);
-    up1.refcount--;
     f1.upvals[ref1.upvalOff] = up2;
-    up2.refcount++;
 };
 
 // This functions are only there for compatibility purposes
diff --git a/src/ldebug.js b/src/ldebug.js
index e403ba6..a471c75 100644
--- a/src/ldebug.js
+++ b/src/ldebug.js
@@ -537,7 +537,7 @@ const isinstack = function(L, ci, o) {
 const getupvalname = function(L, ci, o) {
     let c = ci.func.value;
     for (let i = 0; i < c.nupvalues; i++) {
-        if (c.upvals[i].v === o) {
+        if (c.upvals[i] === o) {
             return {
                 name: upvalname(c.p, i),
                 funcname: to_luastring('upvalue', true)
diff --git a/src/lfunc.js b/src/lfunc.js
index 2f28d0e..198c4b9 100644
--- a/src/lfunc.js
+++ b/src/lfunc.js
@@ -1,7 +1,6 @@
 "use strict";
 
 const { constant_types: { LUA_TNIL } } = require('./defs.js');
-const { lua_assert } = require('./llimits.js');
 const lobject = require('./lobject.js');
 
 class Proto {
@@ -25,22 +24,6 @@ class Proto {
 
 }
 
-class UpVal {
-
-    constructor(L) {
-        this.id = L.l_G.id_counter++;
-        this.v = void 0; /* if open: reference to TValue on stack. if closed: TValue */
-        this.vOff = void 0; /* if open: index on stack. if closed: undefined */
-        this.refcount = 0;
-        this.open_next = null; /* linked list (when open) */
-    }
-
-    isopen() {
-        return this.vOff !== void 0;
-    }
-
-}
-
 const luaF_newLclosure = function(L, n) {
     let c = new lobject.LClosure(L, n);
     return c;
@@ -48,54 +31,24 @@ const luaF_newLclosure = function(L, n) {
 
 
 const luaF_findupval = function(L, level) {
-    let prevp;
-    let p = L.openupval;
-    while (p !== null && p.vOff >= level) {
-        lua_assert(p.isopen());
-        if (p.vOff === level) /* found a corresponding upvalue? */
-            return p; /* return it */
-        prevp = p;
-        p = p.open_next;
-    }
-    /* not found: create a new upvalue */
-    let uv = new UpVal(L);
-    /* link it to list of open upvalues */
-    uv.open_next = p;
-    if (prevp)
-        prevp.open_next = uv;
-    else
-        L.openupval = uv;
-    uv.v = L.stack[level]; /* current value lives in the stack */
-    uv.vOff = level;
-    return uv;
+    return L.stack[level];
 };
 
 const luaF_close = function(L, level) {
-    while (L.openupval !== null && L.openupval.vOff >= level) {
-        let uv = L.openupval;
-        lua_assert(uv.isopen());
-        L.openupval = uv.open_next; /* remove from 'open' list */
-        if (uv.refcount === 0) { /* no references? */
-            /* free upvalue */
-            uv.v = void 0;
-            uv.open_next = null;
-        } else {
-            let from = uv.v;
-            uv.v = new lobject.TValue(from.type, from.value);
-        }
-        uv.vOff = void 0;
+    /* Create new TValues on stack;
+     * any closures will keep referencing old TValues */
+    for (let i=level; i<L.top; i++) {
+        let old = L.stack[i];
+        L.stack[i] = new lobject.TValue(old.type, old.value);
     }
 };
 
 /*
-** fill a closure with new closed upvalues
+** fill a closure with new upvalues
 */
 const luaF_initupvals = function(L, cl) {
     for (let i = 0; i < cl.nupvalues; i++) {
-        let uv = new UpVal(L);
-        uv.refcount = 1;
-        uv.v = new lobject.TValue(LUA_TNIL, null);
-        cl.upvals[i] = uv;
+        cl.upvals[i] = new lobject.TValue(LUA_TNIL, null);
     }
 };
 
@@ -117,7 +70,6 @@ const luaF_getlocalname = function(f, local_number, pc) {
 
 module.exports.MAXUPVAL          = 255;
 module.exports.Proto             = Proto;
-module.exports.UpVal             = UpVal;
 module.exports.luaF_findupval    = luaF_findupval;
 module.exports.luaF_close        = luaF_close;
 module.exports.luaF_getlocalname = luaF_getlocalname;
diff --git a/src/lobject.js b/src/lobject.js
index 34d8550..055ccb2 100644
--- a/src/lobject.js
+++ b/src/lobject.js
@@ -48,7 +48,6 @@ const {
 } = require('./ljstype.js');
 const ldebug  = require('./ldebug.js');
 const ldo     = require('./ldo.js');
-const lfunc   = require('./lfunc.js');
 const lstate  = require('./lstate.js');
 const {
     luaS_bless,
@@ -301,7 +300,7 @@ class LClosure {
 
         this.p = null;
         this.nupvalues = n;
-        this.upvals = new Array(n); /* list of upvalues as UpVals. initialised in luaF_initupvals */
+        this.upvals = new Array(n); /* list of upvalues. initialised in luaF_initupvals */
     }
 
 }
@@ -656,8 +655,7 @@ const luaO_pushvfstring = function(L, fmt, argp) {
                     v instanceof ltable.Table ||
                     v instanceof Udata ||
                     v instanceof LClosure ||
-                    v instanceof CClosure ||
-                    v instanceof lfunc.UpVal) {
+                    v instanceof CClosure) {
                     pushstr(L, to_luastring("0x"+v.id.toString(16)));
                 } else if (v === null) { /* handle null before checking for typeof == object */
                     pushstr(L, to_luastring("null"));
diff --git a/src/lstate.js b/src/lstate.js
index 461ad83..0c44f3c 100644
--- a/src/lstate.js
+++ b/src/lstate.js
@@ -18,7 +18,6 @@ const lobject              = require('./lobject.js');
 const ldo                  = require('./ldo.js');
 const lapi                 = require('./lapi.js');
 const ltable               = require('./ltable.js');
-const lfunc                = require('./lfunc.js');
 const ltm                  = require('./ltm.js');
 
 const EXTRA_STACK = 5;
@@ -70,7 +69,6 @@ class lua_State {
         this.basehookcount = 0;
         this.allowhook = 1;
         this.hookcount = this.basehookcount;
-        this.openupval = null;
         this.nny = 1;
         this.status = LUA_OK;
         this.errfunc = 0;
@@ -166,7 +164,6 @@ const lua_newthread = function(L) {
 };
 
 const luaE_freethread = function(L, L1) {
-    lfunc.luaF_close(L1, L1.stack);
     freestack(L1);
 };
 
@@ -183,7 +180,6 @@ const lua_newstate = function() {
 };
 
 const close_state = function(L) {
-    lfunc.luaF_close(L, L.stack);  /* close all upvalues for this thread */
     freestack(L);
 };
 
diff --git a/src/lvm.js b/src/lvm.js
index 0f184a1..908125f 100644
--- a/src/lvm.js
+++ b/src/lvm.js
@@ -225,11 +225,11 @@ const luaV_execute = function(L) {
             }
             case OP_GETUPVAL: {
                 let b = i.B;
-                lobject.setobj2s(L, ra, cl.upvals[b].v);
+                lobject.setobj2s(L, ra, cl.upvals[b]);
                 break;
             }
             case OP_GETTABUP: {
-                let upval = cl.upvals[i.B].v;
+                let upval = cl.upvals[i.B];
                 let rc = RKC(L, base, k, i);
                 luaV_gettable(L, upval, rc, ra);
                 break;
@@ -241,7 +241,7 @@ const luaV_execute = function(L) {
                 break;
             }
             case OP_SETTABUP: {
-                let upval = cl.upvals[i.A].v;
+                let upval = cl.upvals[i.A];
                 let rb = RKB(L, base, k, i);
                 let rc = RKC(L, base, k, i);
                 settable(L, upval, rb, rc);
@@ -249,7 +249,7 @@ const luaV_execute = function(L) {
             }
             case OP_SETUPVAL: {
                 let uv = cl.upvals[i.B];
-                uv.v.setfrom(L.stack[ra]);
+                uv.setfrom(L.stack[ra]);
                 break;
             }
             case OP_SETTABLE: {
@@ -973,8 +973,8 @@ const getcached = function(p, encup, stack, base) {
         let uv = p.upvalues;
         let nup = uv.length;
         for (let i = 0; i < nup; i++) {  /* check whether it has right upvalues */
-            let v = uv[i].instack ? stack[base + uv[i].idx] : encup[uv[i].idx].v;
-            if (c.upvals[i].v !== v)
+            let v = uv[i].instack ? stack[base + uv[i].idx] : encup[uv[i].idx];
+            if (c.upvals[i] !== v)
                 return null;  /* wrong upvalue; cannot reuse closure */
         }
     }
@@ -996,7 +996,6 @@ const pushclosure = function(L, p, encup, base, ra) {
             ncl.upvals[i] = lfunc.luaF_findupval(L, base + uv[i].idx);
         else
             ncl.upvals[i] = encup[uv[i].idx];
-        ncl.upvals[i].refcount++;
     }
     p.cache = ncl;  /* save it on cache for reuse */
 };