lua.lua/lvm.c

/*
** $Id: lvm.c,v 2.90 2009/06/01 19:09:26 roberto Exp roberto $
** Lua virtual machine
** See Copyright Notice in lua.h
*/


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define lvm_c
#define LUA_CORE

#include "lua.h"

#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#include "lvm.h"



/* limit for table tag-method chains (to avoid loops) */
#define MAXTAGLOOP	100


const TValue *luaV_tonumber (const TValue *obj, TValue *n) {
  lua_Number num;
  if (ttisnumber(obj)) return obj;
  if (ttisstring(obj) && luaO_str2d(svalue(obj), &num)) {
    setnvalue(n, num);
    return n;
  }
  else
    return NULL;
}


int luaV_tostring (lua_State *L, StkId obj) {
  if (!ttisnumber(obj))
    return 0;
  else {
    char s[LUAI_MAXNUMBER2STR];
    lua_Number n = nvalue(obj);
    lua_number2str(s, n);
    setsvalue2s(L, obj, luaS_new(L, s));
    return 1;
  }
}


static void traceexec (lua_State *L) {
  CallInfo *ci = L->ci;
  lu_byte mask = L->hookmask;
  if ((mask & LUA_MASKCOUNT) && L->hookcount == 0) {
    resethookcount(L);
    luaD_callhook(L, LUA_HOOKCOUNT, -1);
  }
  if (mask & LUA_MASKLINE) {
    Proto *p = ci_func(ci)->l.p;
    int npc = pcRel(ci->u.l.savedpc, p);
    int newline = getfuncline(p, npc);
    if (npc == 0 ||  /* call linehook when enter a new function, */
        ci->u.l.savedpc <= L->oldpc ||  /* when jump back (loop), or when */
        newline != getfuncline(p, pcRel(L->oldpc, p)))  /* enter a new line */
      luaD_callhook(L, LUA_HOOKLINE, newline);
  }
  L->oldpc = ci->u.l.savedpc;
}


static void callTM (lua_State *L, const TValue *f, const TValue *p1,
                    const TValue *p2, TValue *p3, int hasres) {
  ptrdiff_t result = savestack(L, p3);
  setobj2s(L, L->top++, f);  /* push function */
  setobj2s(L, L->top++, p1);  /* 1st argument */
  setobj2s(L, L->top++, p2);  /* 2nd argument */
  if (!hasres)  /* no result? 'p3' is third argument */
    setobj2s(L, L->top++, p3);  /* 3th argument */
  luaD_checkstack(L, 0);
  /* metamethod may yield only when called from Lua code */
  luaD_call(L, L->top - (4 - hasres), hasres, isLua(L->ci));
  if (hasres) {  /* if has result, move it to its place */
    p3 = restorestack(L, result);
    setobjs2s(L, p3, --L->top);
  }
}


void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
  int loop;
  for (loop = 0; loop < MAXTAGLOOP; loop++) {
    const TValue *tm;
    if (ttistable(t)) {  /* `t' is a table? */
      Table *h = hvalue(t);
      const TValue *res = luaH_get(h, key); /* do a primitive get */
      if (!ttisnil(res) ||  /* result is no nil? */
          (tm = fasttm(L, h->metatable, TM_INDEX)) == NULL) { /* or no TM? */
        setobj2s(L, val, res);
        return;
      }
      /* else will try the tag method */
    }
    else if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_INDEX)))
      luaG_typeerror(L, t, "index");
    if (ttisfunction(tm)) {
      callTM(L, tm, t, key, val, 1);
      return;
    }
    t = tm;  /* else repeat with `tm' */
  }
  luaG_runerror(L, "loop in gettable");
}


void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
  int loop;
  for (loop = 0; loop < MAXTAGLOOP; loop++) {
    const TValue *tm;
    if (ttistable(t)) {  /* `t' is a table? */
      Table *h = hvalue(t);
      TValue *oldval = luaH_set(L, h, key); /* do a primitive set */
      if (!ttisnil(oldval) ||  /* result is no nil? */
          (tm = fasttm(L, h->metatable, TM_NEWINDEX)) == NULL) { /* or no TM? */
        setobj2t(L, oldval, val);
        luaC_barriert(L, h, val);
        return;
      }
      /* else will try the tag method */
    }
    else if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_NEWINDEX)))
      luaG_typeerror(L, t, "index");
    if (ttisfunction(tm)) {
      callTM(L, tm, t, key, val, 0);
      return;
    }
    t = tm;  /* else repeat with `tm' */
  }
  luaG_runerror(L, "loop in settable");
}


static int call_binTM (lua_State *L, const TValue *p1, const TValue *p2,
                       StkId res, TMS event) {
  const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */
  if (ttisnil(tm))
    tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */
  if (ttisnil(tm)) return 0;
  callTM(L, tm, p1, p2, res, 1);
  return 1;
}


static const TValue *get_compTM (lua_State *L, Table *mt1, Table *mt2,
                                  TMS event) {
  const TValue *tm1 = fasttm(L, mt1, event);
  const TValue *tm2;
  if (tm1 == NULL) return NULL;  /* no metamethod */
  if (mt1 == mt2) return tm1;  /* same metatables => same metamethods */
  tm2 = fasttm(L, mt2, event);
  if (tm2 == NULL) return NULL;  /* no metamethod */
  if (luaO_rawequalObj(tm1, tm2))  /* same metamethods? */
    return tm1;
  return NULL;
}


static int call_orderTM (lua_State *L, const TValue *p1, const TValue *p2,
                         TMS event) {
  const TValue *tm1 = luaT_gettmbyobj(L, p1, event);
  const TValue *tm2;
  if (ttisnil(tm1)) return -1;  /* no metamethod? */
  tm2 = luaT_gettmbyobj(L, p2, event);
  if (!luaO_rawequalObj(tm1, tm2))  /* different metamethods? */
    return -1;
  callTM(L, tm1, p1, p2, L->top, 1);
  return !l_isfalse(L->top);
}


static int l_strcmp (const TString *ls, const TString *rs) {
  const char *l = getstr(ls);
  size_t ll = ls->tsv.len;
  const char *r = getstr(rs);
  size_t lr = rs->tsv.len;
  for (;;) {
    int temp = strcoll(l, r);
    if (temp != 0) return temp;
    else {  /* strings are equal up to a `\0' */
      size_t len = strlen(l);  /* index of first `\0' in both strings */
      if (len == lr)  /* r is finished? */
        return (len == ll) ? 0 : 1;
      else if (len == ll)  /* l is finished? */
        return -1;  /* l is smaller than r (because r is not finished) */
      /* both strings longer than `len'; go on comparing (after the `\0') */
      len++;
      l += len; ll -= len; r += len; lr -= len;
    }
  }
}


int luaV_lessthan (lua_State *L, const TValue *l, const TValue *r) {
  int res;
  if (ttype(l) != ttype(r))
    return luaG_ordererror(L, l, r);
  else if (ttisnumber(l))
    return luai_numlt(L, nvalue(l), nvalue(r));
  else if (ttisstring(l))
    return l_strcmp(rawtsvalue(l), rawtsvalue(r)) < 0;
  else if ((res = call_orderTM(L, l, r, TM_LT)) != -1)
    return res;
  return luaG_ordererror(L, l, r);
}


static int lessequal (lua_State *L, const TValue *l, const TValue *r) {
  int res;
  if (ttype(l) != ttype(r))
    return luaG_ordererror(L, l, r);
  else if (ttisnumber(l))
    return luai_numle(L, nvalue(l), nvalue(r));
  else if (ttisstring(l))
    return l_strcmp(rawtsvalue(l), rawtsvalue(r)) <= 0;
  else if ((res = call_orderTM(L, l, r, TM_LE)) != -1)  /* first try `le' */
    return res;
  else if ((res = call_orderTM(L, r, l, TM_LT)) != -1)  /* else try `lt' */
    return !res;
  return luaG_ordererror(L, l, r);
}


int luaV_equalval_ (lua_State *L, const TValue *t1, const TValue *t2) {
  const TValue *tm;
  lua_assert(ttype(t1) == ttype(t2));
  switch (ttype(t1)) {
    case LUA_TNIL: return 1;
    case LUA_TNUMBER: return luai_numeq(nvalue(t1), nvalue(t2));
    case LUA_TBOOLEAN: return bvalue(t1) == bvalue(t2);  /* true must be 1 !! */
    case LUA_TLIGHTUSERDATA: return pvalue(t1) == pvalue(t2);
    case LUA_TUSERDATA: {
      if (uvalue(t1) == uvalue(t2)) return 1;
      tm = get_compTM(L, uvalue(t1)->metatable, uvalue(t2)->metatable, TM_EQ);
      break;  /* will try TM */
    }
    case LUA_TTABLE: {
      if (hvalue(t1) == hvalue(t2)) return 1;
      tm = get_compTM(L, hvalue(t1)->metatable, hvalue(t2)->metatable, TM_EQ);
      break;  /* will try TM */
    }
    default: return gcvalue(t1) == gcvalue(t2);
  }
  if (tm == NULL) return 0;  /* no TM? */
  callTM(L, tm, t1, t2, L->top, 1);  /* call TM */
  return !l_isfalse(L->top);
}


void luaV_concat (lua_State *L, int total) {
  lua_assert(total >= 2);
  do {
    StkId top = L->top;
    int n = 2;  /* number of elements handled in this pass (at least 2) */
    if (!(ttisstring(top-2) || ttisnumber(top-2)) || !tostring(L, top-1)) {
      if (!call_binTM(L, top-2, top-1, top-2, TM_CONCAT))
        luaG_concaterror(L, top-2, top-1);
    }
    else if (tsvalue(top-1)->len == 0)  /* second operand is empty? */
      (void)tostring(L, top - 2);  /* result is first operand */
    else if (ttisstring(top-2) && tsvalue(top-2)->len == 0) {
      setsvalue2s(L, top-2, rawtsvalue(top-1));  /* result is second op. */
    }
    else {
      /* at least two non-empty string values; get as many as possible */
      size_t tl = tsvalue(top-1)->len;
      char *buffer;
      int i;
      /* collect total length */
      for (n = 1; n < total && tostring(L, top-n-1); n++) {
        size_t l = tsvalue(top-n-1)->len;
        if (l >= MAX_SIZET - tl) luaG_runerror(L, "string length overflow");
        tl += l;
      }
      buffer = luaZ_openspace(L, &G(L)->buff, tl);
      tl = 0;
      for (i=n; i>0; i--) {  /* concat all strings */
        size_t l = tsvalue(top-i)->len;
        memcpy(buffer+tl, svalue(top-i), l);
        tl += l;
      }
      setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl));
    }
    total -= n-1;  /* got 'n' strings to create 1 new */
    L->top -= n-1;  /* poped 'n' strings and pushed one */
  } while (total > 1);  /* repeat until only 1 result left */
}


static void objlen (lua_State *L, StkId ra, const TValue *rb) {
  const TValue *tm;
  switch (ttype(rb)) {
    case LUA_TTABLE: {
      Table *h = hvalue(rb);
      tm = fasttm(L, h->metatable, TM_LEN);
      if (tm) break;  /* metamethod? break switch to call it */
      setnvalue(ra, cast_num(luaH_getn(h)));  /* else primitive len */
      return;
    }
    case LUA_TSTRING: {
      setnvalue(ra, cast_num(tsvalue(rb)->len));
      return;
    }
    default: {  /* try metamethod */
      tm = luaT_gettmbyobj(L, rb, TM_LEN);
      if (ttisnil(tm))  /* no metamethod? */
        luaG_typeerror(L, rb, "get length of");
      break;
    }
  }
  callTM(L, tm, rb, luaO_nilobject, ra, 1);
}


static void Arith (lua_State *L, StkId ra, const TValue *rb,
                   const TValue *rc, TMS op) {
  TValue tempb, tempc;
  const TValue *b, *c;
  if ((b = luaV_tonumber(rb, &tempb)) != NULL &&
      (c = luaV_tonumber(rc, &tempc)) != NULL) {
    lua_Number nb = nvalue(b), nc = nvalue(c);
    switch (op) {
      case TM_ADD: setnvalue(ra, luai_numadd(L, nb, nc)); break;
      case TM_SUB: setnvalue(ra, luai_numsub(L, nb, nc)); break;
      case TM_MUL: setnvalue(ra, luai_nummul(L, nb, nc)); break;
      case TM_DIV: setnvalue(ra, luai_numdiv(L, nb, nc)); break;
      case TM_MOD: setnvalue(ra, luai_nummod(L, nb, nc)); break;
      case TM_POW: setnvalue(ra, luai_numpow(L, nb, nc)); break;
      case TM_UNM: setnvalue(ra, luai_numunm(L, nb)); break;
      default: lua_assert(0); break;
    }
  }
  else if (!call_binTM(L, rb, rc, ra, op))
    luaG_aritherror(L, rb, rc);
}


/*
** finish execution of an opcode interrupted by an yield
*/
void luaV_finishOp (lua_State *L) {
  CallInfo *ci = L->ci;
  StkId base = ci->u.l.base;
  Instruction inst = *(ci->u.l.savedpc - 1);  /* interrupted instruction */
  switch (GET_OPCODE(inst)) {  /* finish its execution */
    case OP_ADD: case OP_SUB: case OP_MUL: case OP_DIV:
    case OP_MOD: case OP_POW: case OP_UNM: case OP_LEN:
    case OP_GETGLOBAL: case OP_GETTABLE: case OP_SELF: {
      setobjs2s(L, base + GETARG_A(inst), --L->top);
      break;
    }
    case OP_LE: case OP_LT: case OP_EQ: {
      int res = !l_isfalse(L->top - 1);
      L->top--;
      /* metamethod should not be called when operand is K */
      lua_assert(!ISK(GETARG_B(inst)));
      if (GET_OPCODE(inst) == OP_LE &&  /* "<=" using "<" instead? */
          ttisnil(luaT_gettmbyobj(L, base + GETARG_B(inst), TM_LE)))
        res = !res;  /* invert result */
      lua_assert(GET_OPCODE(*ci->u.l.savedpc) == OP_JMP);
      if (res != GETARG_A(inst))  /* condition failed? */
        ci->u.l.savedpc++;  /* skip jump instruction */
      break;
    }
    case OP_CONCAT: {
      StkId top = L->top - 1;  /* top when 'call_binTM' was called */
      int b = GETARG_B(inst);      /* first element to concatenate */
      int total = top - 1 - (base + b);  /* elements yet to concatenate */
      setobj2s(L, top - 2, top);  /* put TM result in proper position */
      if (total > 1) {  /* are there elements to concat? */
        L->top = top - 1;  /* top is one after last element (at top-2) */
        luaV_concat(L, total);  /* concat them (may yield again) */
      }
      /* move final result to final position */
      setobj2s(L, ci->u.l.base + GETARG_A(inst), L->top - 1);
      L->top = ci->top;  /* restore top */
      break;
    }
    case OP_TFORCALL: {
      lua_assert(GET_OPCODE(*ci->u.l.savedpc) == OP_TFORLOOP);
      L->top = ci->top;  /* correct top */
      break;
    }
    case OP_CALL: {
      if (GETARG_C(inst) - 1 >= 0)  /* nresults >= 0? */
        L->top = ci->top;  /* adjust results */
      break;
    }
    case OP_TAILCALL: case OP_SETGLOBAL: case OP_SETTABLE:
      break;
    default: lua_assert(0);
  }
}



/*
** some macros for common tasks in `luaV_execute'
*/

#define RA(i)	(base+GETARG_A(i))
/* to be used after possible stack reallocation */
#define RB(i)	check_exp(getBMode(GET_OPCODE(i)) == OpArgR, base+GETARG_B(i))
#define RC(i)	check_exp(getCMode(GET_OPCODE(i)) == OpArgR, base+GETARG_C(i))
#define RKB(i)	check_exp(getBMode(GET_OPCODE(i)) == OpArgK, \
	ISK(GETARG_B(i)) ? k+INDEXK(GETARG_B(i)) : base+GETARG_B(i))
#define RKC(i)	check_exp(getCMode(GET_OPCODE(i)) == OpArgK, \
	ISK(GETARG_C(i)) ? k+INDEXK(GETARG_C(i)) : base+GETARG_C(i))
#define KBx(i)	check_exp(getBMode(GET_OPCODE(i)) == OpArgK, k+GETARG_Bx(i))


#define dojump(i)	{ ci->u.l.savedpc += (i); luai_threadyield(L);}


#define Protect(x)	{ {x;}; base = ci->u.l.base; }


#define arith_op(op,tm) { \
        TValue *rb = RKB(i); \
        TValue *rc = RKC(i); \
        if (ttisnumber(rb) && ttisnumber(rc)) { \
          lua_Number nb = nvalue(rb), nc = nvalue(rc); \
          setnvalue(ra, op(L, nb, nc)); \
        } \
        else \
          Protect(Arith(L, ra, rb, rc, tm)); \
      }



void luaV_execute (lua_State *L) {
  CallInfo *ci = L->ci;
  LClosure *cl = &clvalue(ci->func)->l;
  TValue *k = cl->p->k;
  StkId base = ci->u.l.base;
  lua_assert(isLua(ci));
  /* main loop of interpreter */
  for (;;) {
    Instruction i = *(ci->u.l.savedpc++);
    StkId ra;
    if ((L->hookmask & (LUA_MASKLINE | LUA_MASKCOUNT)) &&
        (--L->hookcount == 0 || L->hookmask & LUA_MASKLINE)) {
      traceexec(L);
      if (L->status == LUA_YIELD) {  /* did hook yield? */
        ci->u.l.savedpc--;  /* undo increment */
        luaD_throw(L, LUA_YIELD);
      }
      base = ci->u.l.base;
    }
    /* warning!! several calls may realloc the stack and invalidate `ra' */
    ra = RA(i);
    lua_assert(base == ci->u.l.base);
    lua_assert(base <= L->top && L->top <= L->stack + L->stacksize);
    switch (GET_OPCODE(i)) {
      case OP_MOVE: {
        setobjs2s(L, ra, RB(i));
        continue;
      }
      case OP_LOADK: {
        setobj2s(L, ra, KBx(i));
        continue;
      }
      case OP_LOADBOOL: {
        setbvalue(ra, GETARG_B(i));
        if (GETARG_C(i)) ci->u.l.savedpc++;  /* skip next instruction (if C) */
        continue;
      }
      case OP_LOADNIL: {
        TValue *rb = RB(i);
        do {
          setnilvalue(rb--);
        } while (rb >= ra);
        continue;
      }
      case OP_GETUPVAL: {
        int b = GETARG_B(i);
        setobj2s(L, ra, cl->upvals[b]->v);
        continue;
      }
      case OP_GETGLOBAL: {
        TValue g;
        TValue *rb = KBx(i);
        sethvalue(L, &g, cl->env);
        lua_assert(ttisstring(rb));
        Protect(luaV_gettable(L, &g, rb, ra));
        continue;
      }
      case OP_GETTABLE: {
        Protect(luaV_gettable(L, RB(i), RKC(i), ra));
        continue;
      }
      case OP_SETGLOBAL: {
        TValue g;
        sethvalue(L, &g, cl->env);
        lua_assert(ttisstring(KBx(i)));
        Protect(luaV_settable(L, &g, KBx(i), ra));
        continue;
      }
      case OP_SETUPVAL: {
        UpVal *uv = cl->upvals[GETARG_B(i)];
        setobj(L, uv->v, ra);
        luaC_barrier(L, uv, ra);
        continue;
      }
      case OP_SETTABLE: {
        Protect(luaV_settable(L, ra, RKB(i), RKC(i)));
        continue;
      }
      case OP_NEWTABLE: {
        int b = GETARG_B(i);
        int c = GETARG_C(i);
        Table *t = luaH_new(L);
        sethvalue(L, ra, t);
        if (b != 0 || c != 0)
          luaH_resize(L, t, luaO_fb2int(b), luaO_fb2int(c));
        Protect(luaC_checkGC(L));
        continue;
      }
      case OP_SELF: {
        StkId rb = RB(i);
        setobjs2s(L, ra+1, rb);
        Protect(luaV_gettable(L, rb, RKC(i), ra));
        continue;
      }
      case OP_ADD: {
        arith_op(luai_numadd, TM_ADD);
        continue;
      }
      case OP_SUB: {
        arith_op(luai_numsub, TM_SUB);
        continue;
      }
      case OP_MUL: {
        arith_op(luai_nummul, TM_MUL);
        continue;
      }
      case OP_DIV: {
        arith_op(luai_numdiv, TM_DIV);
        continue;
      }
      case OP_MOD: {
        arith_op(luai_nummod, TM_MOD);
        continue;
      }
      case OP_POW: {
        arith_op(luai_numpow, TM_POW);
        continue;
      }
      case OP_UNM: {
        TValue *rb = RB(i);
        if (ttisnumber(rb)) {
          lua_Number nb = nvalue(rb);
          setnvalue(ra, luai_numunm(L, nb));
        }
        else {
          Protect(Arith(L, ra, rb, rb, TM_UNM));
        }
        continue;
      }
      case OP_NOT: {
        int res = l_isfalse(RB(i));  /* next assignment may change this value */
        setbvalue(ra, res);
        continue;
      }
      case OP_LEN: {
        Protect(objlen(L, ra, RB(i)));
        continue;
      }
      case OP_CONCAT: {
        int b = GETARG_B(i);
        int c = GETARG_C(i);
        L->top = base + c + 1;  /* mark the end of concat operands */
        Protect(luaV_concat(L, c-b+1); luaC_checkGC(L));
        L->top = ci->top;  /* restore top */
        setobjs2s(L, RA(i), base+b);
        continue;
      }
      case OP_JMP: {
        dojump(GETARG_sBx(i));
        continue;
      }
      case OP_EQ: {
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        Protect(
          if (equalobj(L, rb, rc) == GETARG_A(i))
            dojump(GETARG_sBx(*ci->u.l.savedpc));
        )
        ci->u.l.savedpc++;
        continue;
      }
      case OP_LT: {
        Protect(
          if (luaV_lessthan(L, RKB(i), RKC(i)) == GETARG_A(i))
            dojump(GETARG_sBx(*ci->u.l.savedpc));
        )
        ci->u.l.savedpc++;
        continue;
      }
      case OP_LE: {
        Protect(
          if (lessequal(L, RKB(i), RKC(i)) == GETARG_A(i))
            dojump(GETARG_sBx(*ci->u.l.savedpc));
        )
        ci->u.l.savedpc++;
        continue;
      }
      case OP_TEST: {
        if (GETARG_C(i) ? !l_isfalse(ra) : l_isfalse(ra))
          dojump(GETARG_sBx(*ci->u.l.savedpc));
        ci->u.l.savedpc++;
        continue;
      }
      case OP_TESTSET: {
        TValue *rb = RB(i);
        if (GETARG_C(i) ? !l_isfalse(rb) : l_isfalse(rb)) {
          setobjs2s(L, ra, rb);
          dojump(GETARG_sBx(*ci->u.l.savedpc));
        }
        ci->u.l.savedpc++;
        continue;
      }
      case OP_CALL: {
        int b = GETARG_B(i);
        int nresults = GETARG_C(i) - 1;
        if (b != 0) L->top = ra+b;  /* else previous instruction set top */
        if (luaD_precall(L, ra, nresults)) {  /* C function? */
          if (nresults >= 0) L->top = ci->top;  /* adjust results */
          base = ci->u.l.base;
          continue;
        }
        else {  /* Lua function */
          ci = L->ci;
          ci->callstatus |= CIST_REENTRY;
          break;  /* restart luaV_execute over new Lua function */
        }
      }
      case OP_TAILCALL: {
        int b = GETARG_B(i);
        if (b != 0) L->top = ra+b;  /* else previous instruction set top */
        lua_assert(GETARG_C(i) - 1 == LUA_MULTRET);
        if (luaD_precall(L, ra, LUA_MULTRET)) {  /* C function? */
          base = ci->u.l.base;
          continue;
        }
        else {
          /* tail call: put called frame (n) in place of caller one (o) */
          CallInfo *nci = L->ci;  /* called frame */
          CallInfo *oci = nci->previous;  /* caller frame */
          StkId nfunc = nci->func;  /* called function index */
          StkId ofunc = oci->func;
          int aux;
          if (cl->p->sizep > 0) luaF_close(L, oci->u.l.base);
          oci->u.l.base = ofunc + (nci->u.l.base - nfunc);
          for (aux = 0; nfunc+aux < L->top; aux++)  /* move frame down */
            setobjs2s(L, ofunc + aux, nfunc + aux);
          oci->top = L->top = ofunc + aux;  /* correct top */
          lua_assert(L->top == oci->u.l.base + clvalue(ofunc)->l.p->maxstacksize);
          oci->u.l.savedpc = nci->u.l.savedpc;
          oci->u.l.tailcalls++;  /* one more call lost */
          ci = L->ci = oci;  /* remove new frame */
          break;  /* restart luaV_execute over new Lua function */
        }
      }
      case OP_RETURN: {
        int b = GETARG_B(i);
        if (b != 0) L->top = ra+b-1;
        if (cl->p->sizep > 0) luaF_close(L, base);
        b = luaD_poscall(L, ra);
        if (!(ci->callstatus & CIST_REENTRY))  /* 'ci' still the called one */
          return;  /* external invocation: return */
        else {  /* invocation via reentry: continue execution */
          ci = L->ci;
          if (b) L->top = ci->top;
          lua_assert(isLua(ci));
          lua_assert(GET_OPCODE(*((ci)->u.l.savedpc - 1)) == OP_CALL);
          break;  /* restart luaV_execute over new Lua function */
        }
      }
      case OP_FORLOOP: {
        lua_Number step = nvalue(ra+2);
        lua_Number idx = luai_numadd(L, nvalue(ra), step); /* increment index */
        lua_Number limit = nvalue(ra+1);
        if (luai_numlt(L, 0, step) ? luai_numle(L, idx, limit)
                                   : luai_numle(L, limit, idx)) {
          dojump(GETARG_sBx(i));  /* jump back */
          setnvalue(ra, idx);  /* update internal index... */
          setnvalue(ra+3, idx);  /* ...and external index */
        }
        continue;
      }
      case OP_FORPREP: {
        const TValue *init = ra;
        const TValue *plimit = ra+1;
        const TValue *pstep = ra+2;
        if (!tonumber(init, ra))
          luaG_runerror(L, LUA_QL("for") " initial value must be a number");
        else if (!tonumber(plimit, ra+1))
          luaG_runerror(L, LUA_QL("for") " limit must be a number");
        else if (!tonumber(pstep, ra+2))
          luaG_runerror(L, LUA_QL("for") " step must be a number");
        setnvalue(ra, luai_numsub(L, nvalue(ra), nvalue(pstep)));
        dojump(GETARG_sBx(i));
        continue;
      }
      case OP_TFORCALL: {
        StkId cb = ra + 3;  /* call base */
        setobjs2s(L, cb+2, ra+2);
        setobjs2s(L, cb+1, ra+1);
        setobjs2s(L, cb, ra);
        L->top = cb + 3;  /* func. + 2 args (state and index) */
        Protect(luaD_call(L, cb, GETARG_C(i), 1));
        L->top = ci->top;
        i = *(ci->u.l.savedpc++);  /* go to next instruction */
        ra = RA(i);
        lua_assert(GET_OPCODE(i) == OP_TFORLOOP);
        /* go through */
      }
      case OP_TFORLOOP: {
        if (!ttisnil(ra + 1)) {  /* continue loop? */
          setobjs2s(L, ra, ra + 1);  /* save control variable */
          dojump(GETARG_sBx(i));  /* jump back */
        }
        continue;
      }
      case OP_SETLIST: {
        int n = GETARG_B(i);
        int c = GETARG_C(i);
        int last;
        Table *h;
        if (n == 0) n = cast_int(L->top - ra) - 1;
        if (c == 0) {
          lua_assert(GET_OPCODE(*ci->u.l.savedpc) == OP_EXTRAARG);
          c = GETARG_Ax(*ci->u.l.savedpc++);
        }
        h = hvalue(ra);
        last = ((c-1)*LFIELDS_PER_FLUSH) + n;
        if (last > h->sizearray)  /* needs more space? */
          luaH_resizearray(L, h, last);  /* pre-alloc it at once */
        for (; n > 0; n--) {
          TValue *val = ra+n;
          setobj2t(L, luaH_setnum(L, h, last--), val);
          luaC_barriert(L, h, val);
        }
        L->top = ci->top;  /* correct top (in case of previous open call) */
        continue;
      }
      case OP_CLOSE: {
        luaF_close(L, ra);
        continue;
      }
      case OP_CLOSURE: {
        Proto *p;
        Closure *ncl;
        int nup, j;
        p = cl->p->p[GETARG_Bx(i)];
        nup = p->nups;
        ncl = luaF_newLclosure(L, nup, cl->env);
        ncl->l.p = p;
        setclvalue(L, ra, ncl);
        for (j=0; j<nup; j++) {
          Instruction u = *ci->u.l.savedpc++;
          if (GET_OPCODE(u) == OP_GETUPVAL)
            ncl->l.upvals[j] = cl->upvals[GETARG_B(u)];
          else {
            lua_assert(GET_OPCODE(u) == OP_MOVE);
            ncl->l.upvals[j] = luaF_findupval(L, base + GETARG_B(u));
          }
        }
        Protect(luaC_checkGC(L));
        continue;
      }
      case OP_VARARG: {
        int b = GETARG_B(i) - 1;
        int j;
        int n = cast_int(base - ci->func) - cl->p->numparams - 1;
        if (b == LUA_MULTRET) {
          Protect(luaD_checkstack(L, n));
          ra = RA(i);  /* previous call may change the stack */
          b = n;
          L->top = ra + n;
        }
        for (j = 0; j < b; j++) {
          if (j < n) {
            setobjs2s(L, ra + j, base - n + j);
          }
          else {
            setnilvalue(ra + j);
          }
        }
        continue;
      }
      case OP_EXTRAARG: {
        luaG_runerror(L, "bad opcode");
        return;
      }
    }
    /* function changed (call/return): update pointers */
    lua_assert(ci == L->ci);
    cl = &clvalue(ci->func)->l;
    k = cl->p->k;
    base = ci->u.l.base;
  }
}