text: /*
  ** Public Lua/C API.
  ** Copyright (C) 2005-2017 Mike Pall. See Copyright Notice in luajit.h
  **
  ** Major portions taken verbatim or adapted from the Lua interpreter.
  ** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
  */
  
  #define lj_api_c
  #define LUA_CORE
  
  #include "lj_obj.h"
  #include "lj_gc.h"
  #include "lj_err.h"
  #include "lj_debug.h"
  #include "lj_str.h"
  #include "lj_tab.h"
  #include "lj_func.h"
  #include "lj_udata.h"
  #include "lj_meta.h"
  #include "lj_state.h"
  #include "lj_bc.h"
  #include "lj_frame.h"
  #include "lj_trace.h"
  #include "lj_vm.h"
  #include "lj_strscan.h"
  #include "lj_strfmt.h"
  
  /* -- Common helper functions --------------------------------------------- */
  
  #define api_checknelems(L, n)		api_check(L, (n) <= (L->top - L->base))
  #define api_checkvalidindex(L, i)	api_check(L, (i) != niltv(L))
  
  static TValue *index2adr(lua_State *L, int idx)
  {
    if (idx > 0) {
      TValue *o = L->base + (idx - 1);
      return o < L->top ? o : niltv(L);
    } else if (idx > LUA_REGISTRYINDEX) {
      api_check(L, idx != 0 && -idx <= L->top - L->base);
      return L->top + idx;
    } else if (idx == LUA_GLOBALSINDEX) {
      TValue *o = &G(L)->tmptv;
      settabV(L, o, tabref(L->env));
      return o;
    } else if (idx == LUA_REGISTRYINDEX) {
      return registry(L);
    } else {
      GCfunc *fn = curr_func(L);
      api_check(L, fn->c.gct == ~LJ_TFUNC && !isluafunc(fn));
      if (idx == LUA_ENVIRONINDEX) {
        TValue *o = &G(L)->tmptv;
        settabV(L, o, tabref(fn->c.env));
        return o;
      } else {
        idx = LUA_GLOBALSINDEX - idx;
        return idx <= fn->c.nupvalues ? &fn->c.upvalue[idx-1] : niltv(L);
      }
    }
  }
  
  static TValue *stkindex2adr(lua_State *L, int idx)
  {
    if (idx > 0) {
      TValue *o = L->base + (idx - 1);
      return o < L->top ? o : niltv(L);
    } else {
      api_check(L, idx != 0 && -idx <= L->top - L->base);
      return L->top + idx;
    }
  }
  
  static GCtab *getcurrenv(lua_State *L)
  {
    GCfunc *fn = curr_func(L);
    return fn->c.gct == ~LJ_TFUNC ? tabref(fn->c.env) : tabref(L->env);
  }
  
  /* -- Miscellaneous API functions ----------------------------------------- */
  
  LUA_API int lua_status(lua_State *L)
  {
    return L->status;
  }
  
  LUA_API int lua_checkstack(lua_State *L, int size)
  {
    if (size > LUAI_MAXCSTACK || (L->top - L->base + size) > LUAI_MAXCSTACK) {
      return 0;  /* Stack overflow. */
    } else if (size > 0) {
      lj_state_checkstack(L, (MSize)size);
    }
    return 1;
  }
  
  LUALIB_API void luaL_checkstack(lua_State *L, int size, const char *msg)
  {
    if (!lua_checkstack(L, size))
      lj_err_callerv(L, LJ_ERR_STKOVM, msg);
  }
  
  LUA_API void lua_xmove(lua_State *from, lua_State *to, int n)
  {
    TValue *f, *t;
    if (from == to) return;
    api_checknelems(from, n);
    api_check(from, G(from) == G(to));
    lj_state_checkstack(to, (MSize)n);
    f = from->top;
    t = to->top = to->top + n;
    while (--n >= 0) copyTV(to, --t, --f);
    from->top = f;
  }
  
  LUA_API const lua_Number *lua_version(lua_State *L)
  {
    static const lua_Number version = LUA_VERSION_NUM;
    UNUSED(L);
    return &version;
  }
  
  /* -- Stack manipulation -------------------------------------------------- */
  
  LUA_API int lua_gettop(lua_State *L)
  {
    return (int)(L->top - L->base);
  }
  
  LUA_API void lua_settop(lua_State *L, int idx)
  {
    if (idx >= 0) {
      api_check(L, idx <= tvref(L->maxstack) - L->base);
      if (L->base + idx > L->top) {
        if (L->base + idx >= tvref(L->maxstack))
  	lj_state_growstack(L, (MSize)idx - (MSize)(L->top - L->base));
        do { setnilV(L->top++); } while (L->top < L->base + idx);
      } else {
        L->top = L->base + idx;
      }
    } else {
      api_check(L, -(idx+1) <= (L->top - L->base));
      L->top += idx+1;  /* Shrinks top (idx < 0). */
    }
  }
  
  LUA_API void lua_remove(lua_State *L, int idx)
  {
    TValue *p = stkindex2adr(L, idx);
    api_checkvalidindex(L, p);
    while (++p < L->top) copyTV(L, p-1, p);
    L->top--;
  }
  
  LUA_API void lua_insert(lua_State *L, int idx)
  {
    TValue *q, *p = stkindex2adr(L, idx);
    api_checkvalidindex(L, p);
    for (q = L->top; q > p; q--) copyTV(L, q, q-1);
    copyTV(L, p, L->top);
  }
  
  static void copy_slot(lua_State *L, TValue *f, int idx)
  {
    if (idx == LUA_GLOBALSINDEX) {
      api_check(L, tvistab(f));
      /* NOBARRIER: A thread (i.e. L) is never black. */
      setgcref(L->env, obj2gco(tabV(f)));
    } else if (idx == LUA_ENVIRONINDEX) {
      GCfunc *fn = curr_func(L);
      if (fn->c.gct != ~LJ_TFUNC)
        lj_err_msg(L, LJ_ERR_NOENV);
      api_check(L, tvistab(f));
      setgcref(fn->c.env, obj2gco(tabV(f)));
      lj_gc_barrier(L, fn, f);
    } else {
      TValue *o = index2adr(L, idx);
      api_checkvalidindex(L, o);
      copyTV(L, o, f);
      if (idx < LUA_GLOBALSINDEX)  /* Need a barrier for upvalues. */
        lj_gc_barrier(L, curr_func(L), f);
    }
  }
  
  LUA_API void lua_replace(lua_State *L, int idx)
  {
    api_checknelems(L, 1);
    copy_slot(L, L->top - 1, idx);
    L->top--;
  }
  
  LUA_API void lua_copy(lua_State *L, int fromidx, int toidx)
  {
    copy_slot(L, index2adr(L, fromidx), toidx);
  }
  
  LUA_API void lua_pushvalue(lua_State *L, int idx)
  {
    copyTV(L, L->top, index2adr(L, idx));
    incr_top(L);
  }
  
  /* -- Stack getters ------------------------------------------------------- */
  
  LUA_API int lua_type(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    if (tvisnumber(o)) {
      return LUA_TNUMBER;
  #if LJ_64 && !LJ_GC64
    } else if (tvislightud(o)) {
      return LUA_TLIGHTUSERDATA;
  #endif
    } else if (o == niltv(L)) {
      return LUA_TNONE;
    } else {  /* Magic internal/external tag conversion. ORDER LJ_T */
      uint32_t t = ~itype(o);
  #if LJ_64
      int tt = (int)((U64x(75a06,98042110) >> 4*t) & 15u);
  #else
      int tt = (int)(((t < 8 ? 0x98042110u : 0x75a06u) >> 4*(t&7)) & 15u);
  #endif
      lua_assert(tt != LUA_TNIL || tvisnil(o));
      return tt;
    }
  }
  
  LUALIB_API void luaL_checktype(lua_State *L, int idx, int tt)
  {
    if (lua_type(L, idx) != tt)
      lj_err_argt(L, idx, tt);
  }
  
  LUALIB_API void luaL_checkany(lua_State *L, int idx)
  {
    if (index2adr(L, idx) == niltv(L))
      lj_err_arg(L, idx, LJ_ERR_NOVAL);
  }
  
  LUA_API const char *lua_typename(lua_State *L, int t)
  {
    UNUSED(L);
    return lj_obj_typename[t+1];
  }
  
  LUA_API int lua_iscfunction(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    return tvisfunc(o) && !isluafunc(funcV(o));
  }
  
  LUA_API int lua_isnumber(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    return (tvisnumber(o) || (tvisstr(o) && lj_strscan_number(strV(o), &tmp)));
  }
  
  LUA_API int lua_isstring(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    return (tvisstr(o) || tvisnumber(o));
  }
  
  LUA_API int lua_isuserdata(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    return (tvisudata(o) || tvislightud(o));
  }
  
  LUA_API int lua_rawequal(lua_State *L, int idx1, int idx2)
  {
    cTValue *o1 = index2adr(L, idx1);
    cTValue *o2 = index2adr(L, idx2);
    return (o1 == niltv(L) || o2 == niltv(L)) ? 0 : lj_obj_equal(o1, o2);
  }
  
  LUA_API int lua_equal(lua_State *L, int idx1, int idx2)
  {
    cTValue *o1 = index2adr(L, idx1);
    cTValue *o2 = index2adr(L, idx2);
    if (tvisint(o1) && tvisint(o2)) {
      return intV(o1) == intV(o2);
    } else if (tvisnumber(o1) && tvisnumber(o2)) {
      return numberVnum(o1) == numberVnum(o2);
    } else if (itype(o1) != itype(o2)) {
      return 0;
    } else if (tvispri(o1)) {
      return o1 != niltv(L) && o2 != niltv(L);
  #if LJ_64 && !LJ_GC64
    } else if (tvislightud(o1)) {
      return o1->u64 == o2->u64;
  #endif
    } else if (gcrefeq(o1->gcr, o2->gcr)) {
      return 1;
    } else if (!tvistabud(o1)) {
      return 0;
    } else {
      TValue *base = lj_meta_equal(L, gcV(o1), gcV(o2), 0);
      if ((uintptr_t)base <= 1) {
        return (int)(uintptr_t)base;
      } else {
        L->top = base+2;
        lj_vm_call(L, base, 1+1);
        L->top -= 2+LJ_FR2;
        return tvistruecond(L->top+1+LJ_FR2);
      }
    }
  }
  
  LUA_API int lua_lessthan(lua_State *L, int idx1, int idx2)
  {
    cTValue *o1 = index2adr(L, idx1);
    cTValue *o2 = index2adr(L, idx2);
    if (o1 == niltv(L) || o2 == niltv(L)) {
      return 0;
    } else if (tvisint(o1) && tvisint(o2)) {
      return intV(o1) < intV(o2);
    } else if (tvisnumber(o1) && tvisnumber(o2)) {
      return numberVnum(o1) < numberVnum(o2);
    } else {
      TValue *base = lj_meta_comp(L, o1, o2, 0);
      if ((uintptr_t)base <= 1) {
        return (int)(uintptr_t)base;
      } else {
        L->top = base+2;
        lj_vm_call(L, base, 1+1);
        L->top -= 2+LJ_FR2;
        return tvistruecond(L->top+1+LJ_FR2);
      }
    }
  }
  
  LUA_API lua_Number lua_tonumber(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    if (LJ_LIKELY(tvisnumber(o)))
      return numberVnum(o);
    else if (tvisstr(o) && lj_strscan_num(strV(o), &tmp))
      return numV(&tmp);
    else
      return 0;
  }
  
  LUA_API lua_Number lua_tonumberx(lua_State *L, int idx, int *ok)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    if (LJ_LIKELY(tvisnumber(o))) {
      if (ok) *ok = 1;
      return numberVnum(o);
    } else if (tvisstr(o) && lj_strscan_num(strV(o), &tmp)) {
      if (ok) *ok = 1;
      return numV(&tmp);
    } else {
      if (ok) *ok = 0;
      return 0;
    }
  }
  
  LUALIB_API lua_Number luaL_checknumber(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    if (LJ_LIKELY(tvisnumber(o)))
      return numberVnum(o);
    else if (!(tvisstr(o) && lj_strscan_num(strV(o), &tmp)))
      lj_err_argt(L, idx, LUA_TNUMBER);
    return numV(&tmp);
  }
  
  LUALIB_API lua_Number luaL_optnumber(lua_State *L, int idx, lua_Number def)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    if (LJ_LIKELY(tvisnumber(o)))
      return numberVnum(o);
    else if (tvisnil(o))
      return def;
    else if (!(tvisstr(o) && lj_strscan_num(strV(o), &tmp)))
      lj_err_argt(L, idx, LUA_TNUMBER);
    return numV(&tmp);
  }
  
  LUA_API lua_Integer lua_tointeger(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    lua_Number n;
    if (LJ_LIKELY(tvisint(o))) {
      return intV(o);
    } else if (LJ_LIKELY(tvisnum(o))) {
      n = numV(o);
    } else {
      if (!(tvisstr(o) && lj_strscan_number(strV(o), &tmp)))
        return 0;
      if (tvisint(&tmp))
        return intV(&tmp);
      n = numV(&tmp);
    }
  #if LJ_64
    return (lua_Integer)n;
  #else
    return lj_num2int(n);
  #endif
  }
  
  LUA_API lua_Integer lua_tointegerx(lua_State *L, int idx, int *ok)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    lua_Number n;
    if (LJ_LIKELY(tvisint(o))) {
      if (ok) *ok = 1;
      return intV(o);
    } else if (LJ_LIKELY(tvisnum(o))) {
      n = numV(o);
    } else {
      if (!(tvisstr(o) && lj_strscan_number(strV(o), &tmp))) {
        if (ok) *ok = 0;
        return 0;
      }
      if (tvisint(&tmp)) {
        if (ok) *ok = 1;
        return intV(&tmp);
      }
      n = numV(&tmp);
    }
    if (ok) *ok = 1;
  #if LJ_64
    return (lua_Integer)n;
  #else
    return lj_num2int(n);
  #endif
  }
  
  LUALIB_API lua_Integer luaL_checkinteger(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    lua_Number n;
    if (LJ_LIKELY(tvisint(o))) {
      return intV(o);
    } else if (LJ_LIKELY(tvisnum(o))) {
      n = numV(o);
    } else {
      if (!(tvisstr(o) && lj_strscan_number(strV(o), &tmp)))
        lj_err_argt(L, idx, LUA_TNUMBER);
      if (tvisint(&tmp))
        return (lua_Integer)intV(&tmp);
      n = numV(&tmp);
    }
  #if LJ_64
    return (lua_Integer)n;
  #else
    return lj_num2int(n);
  #endif
  }
  
  LUALIB_API lua_Integer luaL_optinteger(lua_State *L, int idx, lua_Integer def)
  {
    cTValue *o = index2adr(L, idx);
    TValue tmp;
    lua_Number n;
    if (LJ_LIKELY(tvisint(o))) {
      return intV(o);
    } else if (LJ_LIKELY(tvisnum(o))) {
      n = numV(o);
    } else if (tvisnil(o)) {
      return def;
    } else {
      if (!(tvisstr(o) && lj_strscan_number(strV(o), &tmp)))
        lj_err_argt(L, idx, LUA_TNUMBER);
      if (tvisint(&tmp))
        return (lua_Integer)intV(&tmp);
      n = numV(&tmp);
    }
  #if LJ_64
    return (lua_Integer)n;
  #else
    return lj_num2int(n);
  #endif
  }
  
  LUA_API int lua_toboolean(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    return tvistruecond(o);
  }
  
  LUA_API const char *lua_tolstring(lua_State *L, int idx, size_t *len)
  {
    TValue *o = index2adr(L, idx);
    GCstr *s;
    if (LJ_LIKELY(tvisstr(o))) {
      s = strV(o);
    } else if (tvisnumber(o)) {
      lj_gc_check(L);
      o = index2adr(L, idx);  /* GC may move the stack. */
      s = lj_strfmt_number(L, o);
      setstrV(L, o, s);
    } else {
      if (len != NULL) *len = 0;
      return NULL;
    }
    if (len != NULL) *len = s->len;
    return strdata(s);
  }
  
  LUALIB_API const char *luaL_checklstring(lua_State *L, int idx, size_t *len)
  {
    TValue *o = index2adr(L, idx);
    GCstr *s;
    if (LJ_LIKELY(tvisstr(o))) {
      s = strV(o);
    } else if (tvisnumber(o)) {
      lj_gc_check(L);
      o = index2adr(L, idx);  /* GC may move the stack. */
      s = lj_strfmt_number(L, o);
      setstrV(L, o, s);
    } else {
      lj_err_argt(L, idx, LUA_TSTRING);
    }
    if (len != NULL) *len = s->len;
    return strdata(s);
  }
  
  LUALIB_API const char *luaL_optlstring(lua_State *L, int idx,
  				       const char *def, size_t *len)
  {
    TValue *o = index2adr(L, idx);
    GCstr *s;
    if (LJ_LIKELY(tvisstr(o))) {
      s = strV(o);
    } else if (tvisnil(o)) {
      if (len != NULL) *len = def ? strlen(def) : 0;
      return def;
    } else if (tvisnumber(o)) {
      lj_gc_check(L);
      o = index2adr(L, idx);  /* GC may move the stack. */
      s = lj_strfmt_number(L, o);
      setstrV(L, o, s);
    } else {
      lj_err_argt(L, idx, LUA_TSTRING);
    }
    if (len != NULL) *len = s->len;
    return strdata(s);
  }
  
  LUALIB_API int luaL_checkoption(lua_State *L, int idx, const char *def,
  				const char *const lst[])
  {
    ptrdiff_t i;
    const char *s = lua_tolstring(L, idx, NULL);
    if (s == NULL && (s = def) == NULL)
      lj_err_argt(L, idx, LUA_TSTRING);
    for (i = 0; lst[i]; i++)
      if (strcmp(lst[i], s) == 0)
        return (int)i;
    lj_err_argv(L, idx, LJ_ERR_INVOPTM, s);
  }
  
  LUA_API size_t lua_objlen(lua_State *L, int idx)
  {
    TValue *o = index2adr(L, idx);
    if (tvisstr(o)) {
      return strV(o)->len;
    } else if (tvistab(o)) {
      return (size_t)lj_tab_len(tabV(o));
    } else if (tvisudata(o)) {
      return udataV(o)->len;
    } else if (tvisnumber(o)) {
      GCstr *s = lj_strfmt_number(L, o);
      setstrV(L, o, s);
      return s->len;
    } else {
      return 0;
    }
  }
  
  LUA_API lua_CFunction lua_tocfunction(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    if (tvisfunc(o)) {
      BCOp op = bc_op(*mref(funcV(o)->c.pc, BCIns));
      if (op == BC_FUNCC || op == BC_FUNCCW)
        return funcV(o)->c.f;
    }
    return NULL;
  }
  
  LUA_API void *lua_touserdata(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    if (tvisudata(o))
      return uddata(udataV(o));
    else if (tvislightud(o))
      return lightudV(o);
    else
      return NULL;
  }
  
  LUA_API lua_State *lua_tothread(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    return (!tvisthread(o)) ? NULL : threadV(o);
  }
  
  LUA_API const void *lua_topointer(lua_State *L, int idx)
  {
    return lj_obj_ptr(index2adr(L, idx));
  }
  
  /* -- Stack setters (object creation) ------------------------------------- */
  
  LUA_API void lua_pushnil(lua_State *L)
  {
    setnilV(L->top);
    incr_top(L);
  }
  
  LUA_API void lua_pushnumber(lua_State *L, lua_Number n)
  {
    setnumV(L->top, n);
    if (LJ_UNLIKELY(tvisnan(L->top)))
      setnanV(L->top);  /* Canonicalize injected NaNs. */
    incr_top(L);
  }
  
  LUA_API void lua_pushinteger(lua_State *L, lua_Integer n)
  {
    setintptrV(L->top, n);
    incr_top(L);
  }
  
  LUA_API void lua_pushlstring(lua_State *L, const char *str, size_t len)
  {
    GCstr *s;
    lj_gc_check(L);
    s = lj_str_new(L, str, len);
    setstrV(L, L->top, s);
    incr_top(L);
  }
  
  LUA_API void lua_pushstring(lua_State *L, const char *str)
  {
    if (str == NULL) {
      setnilV(L->top);
    } else {
      GCstr *s;
      lj_gc_check(L);
      s = lj_str_newz(L, str);
      setstrV(L, L->top, s);
    }
    incr_top(L);
  }
  
  LUA_API const char *lua_pushvfstring(lua_State *L, const char *fmt,
  				     va_list argp)
  {
    lj_gc_check(L);
    return lj_strfmt_pushvf(L, fmt, argp);
  }
  
  LUA_API const char *lua_pushfstring(lua_State *L, const char *fmt, ...)
  {
    const char *ret;
    va_list argp;
    lj_gc_check(L);
    va_start(argp, fmt);
    ret = lj_strfmt_pushvf(L, fmt, argp);
    va_end(argp);
    return ret;
  }
  
  LUA_API void lua_pushcclosure(lua_State *L, lua_CFunction f, int n)
  {
    GCfunc *fn;
    lj_gc_check(L);
    api_checknelems(L, n);
    fn = lj_func_newC(L, (MSize)n, getcurrenv(L));
    fn->c.f = f;
    L->top -= n;
    while (n--)
      copyTV(L, &fn->c.upvalue[n], L->top+n);
    setfuncV(L, L->top, fn);
    lua_assert(iswhite(obj2gco(fn)));
    incr_top(L);
  }
  
  LUA_API void lua_pushboolean(lua_State *L, int b)
  {
    setboolV(L->top, (b != 0));
    incr_top(L);
  }
  
  LUA_API void lua_pushlightuserdata(lua_State *L, void *p)
  {
    setlightudV(L->top, checklightudptr(L, p));
    incr_top(L);
  }
  
  LUA_API void lua_createtable(lua_State *L, int narray, int nrec)
  {
    lj_gc_check(L);
    settabV(L, L->top, lj_tab_new_ah(L, narray, nrec));
    incr_top(L);
  }
  
  LUALIB_API int luaL_newmetatable(lua_State *L, const char *tname)
  {
    GCtab *regt = tabV(registry(L));
    TValue *tv = lj_tab_setstr(L, regt, lj_str_newz(L, tname));
    if (tvisnil(tv)) {
      GCtab *mt = lj_tab_new(L, 0, 1);
      settabV(L, tv, mt);
      settabV(L, L->top++, mt);
      lj_gc_anybarriert(L, regt);
      return 1;
    } else {
      copyTV(L, L->top++, tv);
      return 0;
    }
  }
  
  LUA_API int lua_pushthread(lua_State *L)
  {
    setthreadV(L, L->top, L);
    incr_top(L);
    return (mainthread(G(L)) == L);
  }
  
  LUA_API lua_State *lua_newthread(lua_State *L)
  {
    lua_State *L1;
    lj_gc_check(L);
    L1 = lj_state_new(L);
    setthreadV(L, L->top, L1);
    incr_top(L);
    return L1;
  }
  
  LUA_API void *lua_newuserdata(lua_State *L, size_t size)
  {
    GCudata *ud;
    lj_gc_check(L);
    if (size > LJ_MAX_UDATA)
      lj_err_msg(L, LJ_ERR_UDATAOV);
    ud = lj_udata_new(L, (MSize)size, getcurrenv(L));
    setudataV(L, L->top, ud);
    incr_top(L);
    return uddata(ud);
  }
  
  LUA_API void lua_concat(lua_State *L, int n)
  {
    api_checknelems(L, n);
    if (n >= 2) {
      n--;
      do {
        TValue *top = lj_meta_cat(L, L->top-1, -n);
        if (top == NULL) {
  	L->top -= n;
  	break;
        }
        n -= (int)(L->top - top);
        L->top = top+2;
        lj_vm_call(L, top, 1+1);
        L->top -= 1+LJ_FR2;
        copyTV(L, L->top-1, L->top+LJ_FR2);
      } while (--n > 0);
    } else if (n == 0) {  /* Push empty string. */
      setstrV(L, L->top, &G(L)->strempty);
      incr_top(L);
    }
    /* else n == 1: nothing to do. */
  }
  
  /* -- Object getters ------------------------------------------------------ */
  
  LUA_API void lua_gettable(lua_State *L, int idx)
  {
    cTValue *v, *t = index2adr(L, idx);
    api_checkvalidindex(L, t);
    v = lj_meta_tget(L, t, L->top-1);
    if (v == NULL) {
      L->top += 2;
      lj_vm_call(L, L->top-2, 1+1);
      L->top -= 2+LJ_FR2;
      v = L->top+1+LJ_FR2;
    }
    copyTV(L, L->top-1, v);
  }
  
  LUA_API void lua_getfield(lua_State *L, int idx, const char *k)
  {
    cTValue *v, *t = index2adr(L, idx);
    TValue key;
    api_checkvalidindex(L, t);
    setstrV(L, &key, lj_str_newz(L, k));
    v = lj_meta_tget(L, t, &key);
    if (v == NULL) {
      L->top += 2;
      lj_vm_call(L, L->top-2, 1+1);
      L->top -= 2+LJ_FR2;
      v = L->top+1+LJ_FR2;
    }
    copyTV(L, L->top, v);
    incr_top(L);
  }
  
  LUA_API void lua_rawget(lua_State *L, int idx)
  {
    cTValue *t = index2adr(L, idx);
    api_check(L, tvistab(t));
    copyTV(L, L->top-1, lj_tab_get(L, tabV(t), L->top-1));
  }
  
  LUA_API void lua_rawgeti(lua_State *L, int idx, int n)
  {
    cTValue *v, *t = index2adr(L, idx);
    api_check(L, tvistab(t));
    v = lj_tab_getint(tabV(t), n);
    if (v) {
      copyTV(L, L->top, v);
    } else {
      setnilV(L->top);
    }
    incr_top(L);
  }
  
  LUA_API int lua_getmetatable(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    GCtab *mt = NULL;
    if (tvistab(o))
      mt = tabref(tabV(o)->metatable);
    else if (tvisudata(o))
      mt = tabref(udataV(o)->metatable);
    else
      mt = tabref(basemt_obj(G(L), o));
    if (mt == NULL)
      return 0;
    settabV(L, L->top, mt);
    incr_top(L);
    return 1;
  }
  
  LUALIB_API int luaL_getmetafield(lua_State *L, int idx, const char *field)
  {
    if (lua_getmetatable(L, idx)) {
      cTValue *tv = lj_tab_getstr(tabV(L->top-1), lj_str_newz(L, field));
      if (tv && !tvisnil(tv)) {
        copyTV(L, L->top-1, tv);
        return 1;
      }
      L->top--;
    }
    return 0;
  }
  
  LUA_API void lua_getfenv(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    api_checkvalidindex(L, o);
    if (tvisfunc(o)) {
      settabV(L, L->top, tabref(funcV(o)->c.env));
    } else if (tvisudata(o)) {
      settabV(L, L->top, tabref(udataV(o)->env));
    } else if (tvisthread(o)) {
      settabV(L, L->top, tabref(threadV(o)->env));
    } else {
      setnilV(L->top);
    }
    incr_top(L);
  }
  
  LUA_API int lua_next(lua_State *L, int idx)
  {
    cTValue *t = index2adr(L, idx);
    int more;
    api_check(L, tvistab(t));
    more = lj_tab_next(L, tabV(t), L->top-1);
    if (more) {
      incr_top(L);  /* Return new key and value slot. */
    } else {  /* End of traversal. */
      L->top--;  /* Remove key slot. */
    }
    return more;
  }
  
  LUA_API const char *lua_getupvalue(lua_State *L, int idx, int n)
  {
    TValue *val;
    const char *name = lj_debug_uvnamev(index2adr(L, idx), (uint32_t)(n-1), &val);
    if (name) {
      copyTV(L, L->top, val);
      incr_top(L);
    }
    return name;
  }
  
  LUA_API void *lua_upvalueid(lua_State *L, int idx, int n)
  {
    GCfunc *fn = funcV(index2adr(L, idx));
    n--;
    api_check(L, (uint32_t)n < fn->l.nupvalues);
    return isluafunc(fn) ? (void *)gcref(fn->l.uvptr[n]) :
  			 (void *)&fn->c.upvalue[n];
  }
  
  LUA_API void lua_upvaluejoin(lua_State *L, int idx1, int n1, int idx2, int n2)
  {
    GCfunc *fn1 = funcV(index2adr(L, idx1));
    GCfunc *fn2 = funcV(index2adr(L, idx2));
    n1--; n2--;
    api_check(L, isluafunc(fn1) && (uint32_t)n1 < fn1->l.nupvalues);
    api_check(L, isluafunc(fn2) && (uint32_t)n2 < fn2->l.nupvalues);
    setgcrefr(fn1->l.uvptr[n1], fn2->l.uvptr[n2]);
    lj_gc_objbarrier(L, fn1, gcref(fn1->l.uvptr[n1]));
  }
  
  LUALIB_API void *luaL_testudata(lua_State *L, int idx, const char *tname)
  {
    cTValue *o = index2adr(L, idx);
    if (tvisudata(o)) {
      GCudata *ud = udataV(o);
      cTValue *tv = lj_tab_getstr(tabV(registry(L)), lj_str_newz(L, tname));
      if (tv && tvistab(tv) && tabV(tv) == tabref(ud->metatable))
        return uddata(ud);
    }
    return NULL;  /* value is not a userdata with a metatable */
  }
  
  LUALIB_API void *luaL_checkudata(lua_State *L, int idx, const char *tname)
  {
    void *p = luaL_testudata(L, idx, tname);
    if (!p) lj_err_argtype(L, idx, tname);
    return p;
  }
  
  /* -- Object setters ------------------------------------------------------ */
  
  LUA_API void lua_settable(lua_State *L, int idx)
  {
    TValue *o;
    cTValue *t = index2adr(L, idx);
    api_checknelems(L, 2);
    api_checkvalidindex(L, t);
    o = lj_meta_tset(L, t, L->top-2);
    if (o) {
      /* NOBARRIER: lj_meta_tset ensures the table is not black. */
      L->top -= 2;
      copyTV(L, o, L->top+1);
    } else {
      TValue *base = L->top;
      copyTV(L, base+2, base-3-2*LJ_FR2);
      L->top = base+3;
      lj_vm_call(L, base, 0+1);
      L->top -= 3+LJ_FR2;
    }
  }
  
  LUA_API void lua_setfield(lua_State *L, int idx, const char *k)
  {
    TValue *o;
    TValue key;
    cTValue *t = index2adr(L, idx);
    api_checknelems(L, 1);
    api_checkvalidindex(L, t);
    setstrV(L, &key, lj_str_newz(L, k));
    o = lj_meta_tset(L, t, &key);
    if (o) {
      /* NOBARRIER: lj_meta_tset ensures the table is not black. */
      copyTV(L, o, --L->top);
    } else {
      TValue *base = L->top;
      copyTV(L, base+2, base-3-2*LJ_FR2);
      L->top = base+3;
      lj_vm_call(L, base, 0+1);
      L->top -= 2+LJ_FR2;
    }
  }
  
  LUA_API void lua_rawset(lua_State *L, int idx)
  {
    GCtab *t = tabV(index2adr(L, idx));
    TValue *dst, *key;
    api_checknelems(L, 2);
    key = L->top-2;
    dst = lj_tab_set(L, t, key);
    copyTV(L, dst, key+1);
    lj_gc_anybarriert(L, t);
    L->top = key;
  }
  
  LUA_API void lua_rawseti(lua_State *L, int idx, int n)
  {
    GCtab *t = tabV(index2adr(L, idx));
    TValue *dst, *src;
    api_checknelems(L, 1);
    dst = lj_tab_setint(L, t, n);
    src = L->top-1;
    copyTV(L, dst, src);
    lj_gc_barriert(L, t, dst);
    L->top = src;
  }
  
  LUA_API int lua_setmetatable(lua_State *L, int idx)
  {
    global_State *g;
    GCtab *mt;
    cTValue *o = index2adr(L, idx);
    api_checknelems(L, 1);
    api_checkvalidindex(L, o);
    if (tvisnil(L->top-1)) {
      mt = NULL;
    } else {
      api_check(L, tvistab(L->top-1));
      mt = tabV(L->top-1);
    }
    g = G(L);
    if (tvistab(o)) {
      setgcref(tabV(o)->metatable, obj2gco(mt));
      if (mt)
        lj_gc_objbarriert(L, tabV(o), mt);
    } else if (tvisudata(o)) {
      setgcref(udataV(o)->metatable, obj2gco(mt));
      if (mt)
        lj_gc_objbarrier(L, udataV(o), mt);
    } else {
      /* Flush cache, since traces specialize to basemt. But not during __gc. */
      if (lj_trace_flushall(L))
        lj_err_caller(L, LJ_ERR_NOGCMM);
      if (tvisbool(o)) {
        /* NOBARRIER: basemt is a GC root. */
        setgcref(basemt_it(g, LJ_TTRUE), obj2gco(mt));
        setgcref(basemt_it(g, LJ_TFALSE), obj2gco(mt));
      } else {
        /* NOBARRIER: basemt is a GC root. */
        setgcref(basemt_obj(g, o), obj2gco(mt));
      }
    }
    L->top--;
    return 1;
  }
  
  LUALIB_API void luaL_setmetatable(lua_State *L, const char *tname)
  {
    lua_getfield(L, LUA_REGISTRYINDEX, tname);
    lua_setmetatable(L, -2);
  }
  
  LUA_API int lua_setfenv(lua_State *L, int idx)
  {
    cTValue *o = index2adr(L, idx);
    GCtab *t;
    api_checknelems(L, 1);
    api_checkvalidindex(L, o);
    api_check(L, tvistab(L->top-1));
    t = tabV(L->top-1);
    if (tvisfunc(o)) {
      setgcref(funcV(o)->c.env, obj2gco(t));
    } else if (tvisudata(o)) {
      setgcref(udataV(o)->env, obj2gco(t));
    } else if (tvisthread(o)) {
      setgcref(threadV(o)->env, obj2gco(t));
    } else {
      L->top--;
      return 0;
    }
    lj_gc_objbarrier(L, gcV(o), t);
    L->top--;
    return 1;
  }
  
  LUA_API const char *lua_setupvalue(lua_State *L, int idx, int n)
  {
    cTValue *f = index2adr(L, idx);
    TValue *val;
    const char *name;
    api_checknelems(L, 1);
    name = lj_debug_uvnamev(f, (uint32_t)(n-1), &val);
    if (name) {
      L->top--;
      copyTV(L, val, L->top);
      lj_gc_barrier(L, funcV(f), L->top);
    }
    return name;
  }
  
  /* -- Calls --------------------------------------------------------------- */
  
  #if LJ_FR2
  static TValue *api_call_base(lua_State *L, int nargs)
  {
    TValue *o = L->top, *base = o - nargs;
    L->top = o+1;
    for (; o > base; o--) copyTV(L, o, o-1);
    setnilV(o);
    return o+1;
  }
  #else
  #define api_call_base(L, nargs)	(L->top - (nargs))
  #endif
  
  LUA_API void lua_call(lua_State *L, int nargs, int nresults)
  {
    api_check(L, L->status == LUA_OK || L->status == LUA_ERRERR);
    api_checknelems(L, nargs+1);
    lj_vm_call(L, api_call_base(L, nargs), nresults+1);
  }
  
  LUA_API int lua_pcall(lua_State *L, int nargs, int nresults, int errfunc)
  {
    global_State *g = G(L);
    uint8_t oldh = hook_save(g);
    ptrdiff_t ef;
    int status;
    api_check(L, L->status == LUA_OK || L->status == LUA_ERRERR);
    api_checknelems(L, nargs+1);
    if (errfunc == 0) {
      ef = 0;
    } else {
      cTValue *o = stkindex2adr(L, errfunc);
      api_checkvalidindex(L, o);
      ef = savestack(L, o);
    }
    status = lj_vm_pcall(L, api_call_base(L, nargs), nresults+1, ef);
    if (status) hook_restore(g, oldh);
    return status;
  }
  
  static TValue *cpcall(lua_State *L, lua_CFunction func, void *ud)
  {
    GCfunc *fn = lj_func_newC(L, 0, getcurrenv(L));
    TValue *top = L->top;
    fn->c.f = func;
    setfuncV(L, top++, fn);
    if (LJ_FR2) setnilV(top++);
    setlightudV(top++, checklightudptr(L, ud));
    cframe_nres(L->cframe) = 1+0;  /* Zero results. */
    L->top = top;
    return top-1;  /* Now call the newly allocated C function. */
  }
  
  LUA_API int lua_cpcall(lua_State *L, lua_CFunction func, void *ud)
  {
    global_State *g = G(L);
    uint8_t oldh = hook_save(g);
    int status;
    api_check(L, L->status == LUA_OK || L->status == LUA_ERRERR);
    status = lj_vm_cpcall(L, func, ud, cpcall);
    if (status) hook_restore(g, oldh);
    return status;
  }
  
  LUALIB_API int luaL_callmeta(lua_State *L, int idx, const char *field)
  {
    if (luaL_getmetafield(L, idx, field)) {
      TValue *top = L->top--;
      if (LJ_FR2) setnilV(top++);
      copyTV(L, top++, index2adr(L, idx));
      L->top = top;
      lj_vm_call(L, top-1, 1+1);
      return 1;
    }
    return 0;
  }
  
  /* -- Coroutine yield and resume ------------------------------------------ */
  
  LUA_API int lua_isyieldable(lua_State *L)
  {
    return cframe_canyield(L->cframe);
  }
  
  LUA_API int lua_yield(lua_State *L, int nresults)
  {
    void *cf = L->cframe;
    global_State *g = G(L);
    if (cframe_canyield(cf)) {
      cf = cframe_raw(cf);
      if (!hook_active(g)) {  /* Regular yield: move results down if needed. */
        cTValue *f = L->top - nresults;
        if (f > L->base) {
  	TValue *t = L->base;
  	while (--nresults >= 0) copyTV(L, t++, f++);
  	L->top = t;
        }
        L->cframe = NULL;
        L->status = LUA_YIELD;
        return -1;
      } else {  /* Yield from hook: add a pseudo-frame. */
        TValue *top = L->top;
        hook_leave(g);
        (top++)->u64 = cframe_multres(cf);
        setcont(top, lj_cont_hook);
        if (LJ_FR2) top++;
        setframe_pc(top, cframe_pc(cf)-1);
        if (LJ_FR2) top++;
        setframe_gc(top, obj2gco(L), LJ_TTHREAD);
        setframe_ftsz(top, ((char *)(top+1)-(char *)L->base)+FRAME_CONT);
        L->top = L->base = top+1;
  #if LJ_TARGET_X64
        lj_err_throw(L, LUA_YIELD);
  #else
        L->cframe = NULL;
        L->status = LUA_YIELD;
        lj_vm_unwind_c(cf, LUA_YIELD);
  #endif
      }
    }
    lj_err_msg(L, LJ_ERR_CYIELD);
    return 0;  /* unreachable */
  }
  
  LUA_API int lua_resume(lua_State *L, int nargs)
  {
    if (L->cframe == NULL && L->status <= LUA_YIELD)
      return lj_vm_resume(L,
        L->status == LUA_OK ? api_call_base(L, nargs) : L->top - nargs,
        0, 0);
    L->top = L->base;
    setstrV(L, L->top, lj_err_str(L, LJ_ERR_COSUSP));
    incr_top(L);
    return LUA_ERRRUN;
  }
  
  /* -- GC and memory management -------------------------------------------- */
  
  LUA_API int lua_gc(lua_State *L, int what, int data)
  {
    global_State *g = G(L);
    int res = 0;
    switch (what) {
    case LUA_GCSTOP:
      g->gc.threshold = LJ_MAX_MEM;
      break;
    case LUA_GCRESTART:
      g->gc.threshold = data == -1 ? (g->gc.total/100)*g->gc.pause : g->gc.total;
      break;
    case LUA_GCCOLLECT:
      lj_gc_fullgc(L);
      break;
    case LUA_GCCOUNT:
      res = (int)(g->gc.total >> 10);
      break;
    case LUA_GCCOUNTB:
      res = (int)(g->gc.total & 0x3ff);
      break;
    case LUA_GCSTEP: {
      GCSize a = (GCSize)data << 10;
      g->gc.threshold = (a <= g->gc.total) ? (g->gc.total - a) : 0;
      while (g->gc.total >= g->gc.threshold)
        if (lj_gc_step(L) > 0) {
  	res = 1;
  	break;
        }
      break;
    }
    case LUA_GCSETPAUSE:
      res = (int)(g->gc.pause);
      g->gc.pause = (MSize)data;
      break;
    case LUA_GCSETSTEPMUL:
      res = (int)(g->gc.stepmul);
      g->gc.stepmul = (MSize)data;
      break;
    case LUA_GCISRUNNING:
      res = (g->gc.threshold != LJ_MAX_MEM);
      break;
    default:
      res = -1;  /* Invalid option. */
    }
    return res;
  }
  
  LUA_API lua_Alloc lua_getallocf(lua_State *L, void **ud)
  {
    global_State *g = G(L);
    if (ud) *ud = g->allocd;
    return g->allocf;
  }
  
  LUA_API void lua_setallocf(lua_State *L, lua_Alloc f, void *ud)
  {
    global_State *g = G(L);
    g->allocd = ud;
    g->allocf = f;
  }
  
  