lua

lparser.c (57937B)

---

 /*
 ** $Id: lparser.c $
 ** Lua Parser
 ** See Copyright Notice in lua.h
 */
 
 #define lparser_c
 #define LUA_CORE
 
 #include "lprefix.h"
 
 
 #include <limits.h>
 #include <string.h>
 
 #include "lua.h"
 
 #include "lcode.h"
 #include "ldebug.h"
 #include "ldo.h"
 #include "lfunc.h"
 #include "llex.h"
 #include "lmem.h"
 #include "lobject.h"
 #include "lopcodes.h"
 #include "lparser.h"
 #include "lstate.h"
 #include "lstring.h"
 #include "ltable.h"
 
 
 
 /* maximum number of local variables per function (must be smaller
    than 250, due to the bytecode format) */
 #define MAXVARS		200
 
 
 #define hasmultret(k)		((k) == VCALL || (k) == VVARARG)
 
 
 /* because all strings are unified by the scanner, the parser
    can use pointer equality for string equality */
 #define eqstr(a,b)	((a) == (b))
 
 
 /*
 ** nodes for block list (list of active blocks)
 */
 typedef struct BlockCnt {
   struct BlockCnt *previous;  /* chain */
   int firstlabel;  /* index of first label in this block */
   int firstgoto;  /* index of first pending goto in this block */
   lu_byte nactvar;  /* # active locals outside the block */
   lu_byte upval;  /* true if some variable in the block is an upvalue */
   lu_byte isloop;  /* 1 if 'block' is a loop; 2 if it has pending breaks */
   lu_byte insidetbc;  /* true if inside the scope of a to-be-closed var. */
 } BlockCnt;
 
 
 
 /*
 ** prototypes for recursive non-terminal functions
 */
 static void statement (LexState *ls);
 static void expr (LexState *ls, expdesc *v);
 
 
 static l_noret error_expected (LexState *ls, int token) {
   luaX_syntaxerror(ls,
       luaO_pushfstring(ls->L, "%s expected", luaX_token2str(ls, token)));
 }
 
 
 static l_noret errorlimit (FuncState *fs, int limit, const char *what) {
   lua_State *L = fs->ls->L;
   const char *msg;
   int line = fs->f->linedefined;
   const char *where = (line == 0)
                       ? "main function"
                       : luaO_pushfstring(L, "function at line %d", line);
   msg = luaO_pushfstring(L, "too many %s (limit is %d) in %s",
                              what, limit, where);
   luaX_syntaxerror(fs->ls, msg);
 }
 
 
 void luaY_checklimit (FuncState *fs, int v, int l, const char *what) {
   if (l_unlikely(v > l)) errorlimit(fs, l, what);
 }
 
 
 /*
 ** Test whether next token is 'c'; if so, skip it.
 */
 static int testnext (LexState *ls, int c) {
   if (ls->t.token == c) {
     luaX_next(ls);
     return 1;
   }
   else return 0;
 }
 
 
 /*
 ** Check that next token is 'c'.
 */
 static void check (LexState *ls, int c) {
   if (ls->t.token != c)
     error_expected(ls, c);
 }
 
 
 /*
 ** Check that next token is 'c' and skip it.
 */
 static void checknext (LexState *ls, int c) {
   check(ls, c);
   luaX_next(ls);
 }
 
 
 #define check_condition(ls,c,msg)	{ if (!(c)) luaX_syntaxerror(ls, msg); }
 
 
 /*
 ** Check that next token is 'what' and skip it. In case of error,
 ** raise an error that the expected 'what' should match a 'who'
 ** in line 'where' (if that is not the current line).
 */
 static void check_match (LexState *ls, int what, int who, int where) {
   if (l_unlikely(!testnext(ls, what))) {
     if (where == ls->linenumber)  /* all in the same line? */
       error_expected(ls, what);  /* do not need a complex message */
     else {
       luaX_syntaxerror(ls, luaO_pushfstring(ls->L,
              "%s expected (to close %s at line %d)",
               luaX_token2str(ls, what), luaX_token2str(ls, who), where));
     }
   }
 }
 
 
 static TString *str_checkname (LexState *ls) {
   TString *ts;
   check(ls, TK_NAME);
   ts = ls->t.seminfo.ts;
   luaX_next(ls);
   return ts;
 }
 
 
 static void init_exp (expdesc *e, expkind k, int i) {
   e->f = e->t = NO_JUMP;
   e->k = k;
   e->u.info = i;
 }
 
 
 static void codestring (expdesc *e, TString *s) {
   e->f = e->t = NO_JUMP;
   e->k = VKSTR;
   e->u.strval = s;
 }
 
 
 static void codename (LexState *ls, expdesc *e) {
   codestring(e, str_checkname(ls));
 }
 
 
 /*
 ** Register a new local variable in the active 'Proto' (for debug
 ** information).
 */
 static short registerlocalvar (LexState *ls, FuncState *fs,
                                TString *varname) {
   Proto *f = fs->f;
   int oldsize = f->sizelocvars;
   luaM_growvector(ls->L, f->locvars, fs->ndebugvars, f->sizelocvars,
                   LocVar, SHRT_MAX, "local variables");
   while (oldsize < f->sizelocvars)
     f->locvars[oldsize++].varname = NULL;
   f->locvars[fs->ndebugvars].varname = varname;
   f->locvars[fs->ndebugvars].startpc = fs->pc;
   luaC_objbarrier(ls->L, f, varname);
   return fs->ndebugvars++;
 }
 
 
 /*
 ** Create a new local variable with the given 'name' and given 'kind'.
 ** Return its index in the function.
 */
 static int new_localvarkind (LexState *ls, TString *name, lu_byte kind) {
   lua_State *L = ls->L;
   FuncState *fs = ls->fs;
   Dyndata *dyd = ls->dyd;
   Vardesc *var;
   luaY_checklimit(fs, dyd->actvar.n + 1 - fs->firstlocal,
                  MAXVARS, "local variables");
   luaM_growvector(L, dyd->actvar.arr, dyd->actvar.n + 1,
                   dyd->actvar.size, Vardesc, SHRT_MAX, "local variables");
   var = &dyd->actvar.arr[dyd->actvar.n++];
   var->vd.kind = kind;  /* default */
   var->vd.name = name;
   return dyd->actvar.n - 1 - fs->firstlocal;
 }
 
 
 /*
 ** Create a new local variable with the given 'name' and regular kind.
 */
 static int new_localvar (LexState *ls, TString *name) {
   return new_localvarkind(ls, name, VDKREG);
 }
 
 #define new_localvarliteral(ls,v) \
     new_localvar(ls,  \
       luaX_newstring(ls, "" v, (sizeof(v)/sizeof(char)) - 1));
 
 
 
 /*
 ** Return the "variable description" (Vardesc) of a given variable.
 ** (Unless noted otherwise, all variables are referred to by their
 ** compiler indices.)
 */
 static Vardesc *getlocalvardesc (FuncState *fs, int vidx) {
   return &fs->ls->dyd->actvar.arr[fs->firstlocal + vidx];
 }
 
 
 /*
 ** Convert 'nvar', a compiler index level, to its corresponding
 ** register. For that, search for the highest variable below that level
 ** that is in a register and uses its register index ('ridx') plus one.
 */
 static lu_byte reglevel (FuncState *fs, int nvar) {
   while (nvar-- > 0) {
     Vardesc *vd = getlocalvardesc(fs, nvar);  /* get previous variable */
     if (vd->vd.kind != RDKCTC)  /* is in a register? */
       return cast_byte(vd->vd.ridx + 1);
   }
   return 0;  /* no variables in registers */
 }
 
 
 /*
 ** Return the number of variables in the register stack for the given
 ** function.
 */
 lu_byte luaY_nvarstack (FuncState *fs) {
   return reglevel(fs, fs->nactvar);
 }
 
 
 /*
 ** Get the debug-information entry for current variable 'vidx'.
 */
 static LocVar *localdebuginfo (FuncState *fs, int vidx) {
   Vardesc *vd = getlocalvardesc(fs,  vidx);
   if (vd->vd.kind == RDKCTC)
     return NULL;  /* no debug info. for constants */
   else {
     int idx = vd->vd.pidx;
     lua_assert(idx < fs->ndebugvars);
     return &fs->f->locvars[idx];
   }
 }
 
 
 /*
 ** Create an expression representing variable 'vidx'
 */
 static void init_var (FuncState *fs, expdesc *e, int vidx) {
   e->f = e->t = NO_JUMP;
   e->k = VLOCAL;
   e->u.var.vidx = cast(unsigned short, vidx);
   e->u.var.ridx = getlocalvardesc(fs, vidx)->vd.ridx;
 }
 
 
 /*
 ** Raises an error if variable described by 'e' is read only
 */
 static void check_readonly (LexState *ls, expdesc *e) {
   FuncState *fs = ls->fs;
   TString *varname = NULL;  /* to be set if variable is const */
   switch (e->k) {
     case VCONST: {
       varname = ls->dyd->actvar.arr[e->u.info].vd.name;
       break;
     }
     case VLOCAL: {
       Vardesc *vardesc = getlocalvardesc(fs, e->u.var.vidx);
       if (vardesc->vd.kind != VDKREG)  /* not a regular variable? */
         varname = vardesc->vd.name;
       break;
     }
     case VUPVAL: {
       Upvaldesc *up = &fs->f->upvalues[e->u.info];
       if (up->kind != VDKREG)
         varname = up->name;
       break;
     }
     default:
       return;  /* other cases cannot be read-only */
   }
   if (varname) {
     const char *msg = luaO_pushfstring(ls->L,
        "attempt to assign to const variable '%s'", getstr(varname));
     luaK_semerror(ls, msg);  /* error */
   }
 }
 
 
 /*
 ** Start the scope for the last 'nvars' created variables.
 */
 static void adjustlocalvars (LexState *ls, int nvars) {
   FuncState *fs = ls->fs;
   int reglevel = luaY_nvarstack(fs);
   int i;
   for (i = 0; i < nvars; i++) {
     int vidx = fs->nactvar++;
     Vardesc *var = getlocalvardesc(fs, vidx);
     var->vd.ridx = cast_byte(reglevel++);
     var->vd.pidx = registerlocalvar(ls, fs, var->vd.name);
   }
 }
 
 
 /*
 ** Close the scope for all variables up to level 'tolevel'.
 ** (debug info.)
 */
 static void removevars (FuncState *fs, int tolevel) {
   fs->ls->dyd->actvar.n -= (fs->nactvar - tolevel);
   while (fs->nactvar > tolevel) {
     LocVar *var = localdebuginfo(fs, --fs->nactvar);
     if (var)  /* does it have debug information? */
       var->endpc = fs->pc;
   }
 }
 
 
 /*
 ** Search the upvalues of the function 'fs' for one
 ** with the given 'name'.
 */
 static int searchupvalue (FuncState *fs, TString *name) {
   int i;
   Upvaldesc *up = fs->f->upvalues;
   for (i = 0; i < fs->nups; i++) {
     if (eqstr(up[i].name, name)) return i;
   }
   return -1;  /* not found */
 }
 
 
 static Upvaldesc *allocupvalue (FuncState *fs) {
   Proto *f = fs->f;
   int oldsize = f->sizeupvalues;
   luaY_checklimit(fs, fs->nups + 1, MAXUPVAL, "upvalues");
   luaM_growvector(fs->ls->L, f->upvalues, fs->nups, f->sizeupvalues,
                   Upvaldesc, MAXUPVAL, "upvalues");
   while (oldsize < f->sizeupvalues)
     f->upvalues[oldsize++].name = NULL;
   return &f->upvalues[fs->nups++];
 }
 
 
 static int newupvalue (FuncState *fs, TString *name, expdesc *v) {
   Upvaldesc *up = allocupvalue(fs);
   FuncState *prev = fs->prev;
   if (v->k == VLOCAL) {
     up->instack = 1;
     up->idx = v->u.var.ridx;
     up->kind = getlocalvardesc(prev, v->u.var.vidx)->vd.kind;
     lua_assert(eqstr(name, getlocalvardesc(prev, v->u.var.vidx)->vd.name));
   }
   else {
     up->instack = 0;
     up->idx = cast_byte(v->u.info);
     up->kind = prev->f->upvalues[v->u.info].kind;
     lua_assert(eqstr(name, prev->f->upvalues[v->u.info].name));
   }
   up->name = name;
   luaC_objbarrier(fs->ls->L, fs->f, name);
   return fs->nups - 1;
 }
 
 
 /*
 ** Look for an active local variable with the name 'n' in the
 ** function 'fs'. If found, initialize 'var' with it and return
 ** its expression kind; otherwise return -1.
 */
 static int searchvar (FuncState *fs, TString *n, expdesc *var) {
   int i;
   for (i = cast_int(fs->nactvar) - 1; i >= 0; i--) {
     Vardesc *vd = getlocalvardesc(fs, i);
     if (eqstr(n, vd->vd.name)) {  /* found? */
       if (vd->vd.kind == RDKCTC)  /* compile-time constant? */
         init_exp(var, VCONST, fs->firstlocal + i);
       else  /* real variable */
         init_var(fs, var, i);
       return cast_int(var->k);
     }
   }
   return -1;  /* not found */
 }
 
 
 /*
 ** Mark block where variable at given level was defined
 ** (to emit close instructions later).
 */
 static void markupval (FuncState *fs, int level) {
   BlockCnt *bl = fs->bl;
   while (bl->nactvar > level)
     bl = bl->previous;
   bl->upval = 1;
   fs->needclose = 1;
 }
 
 
 /*
 ** Mark that current block has a to-be-closed variable.
 */
 static void marktobeclosed (FuncState *fs) {
   BlockCnt *bl = fs->bl;
   bl->upval = 1;
   bl->insidetbc = 1;
   fs->needclose = 1;
 }
 
 
 /*
 ** Find a variable with the given name 'n'. If it is an upvalue, add
 ** this upvalue into all intermediate functions. If it is a global, set
 ** 'var' as 'void' as a flag.
 */
 static void singlevaraux (FuncState *fs, TString *n, expdesc *var, int base) {
   if (fs == NULL)  /* no more levels? */
     init_exp(var, VVOID, 0);  /* default is global */
   else {
     int v = searchvar(fs, n, var);  /* look up locals at current level */
     if (v >= 0) {  /* found? */
       if (v == VLOCAL && !base)
         markupval(fs, var->u.var.vidx);  /* local will be used as an upval */
     }
     else {  /* not found as local at current level; try upvalues */
       int idx = searchupvalue(fs, n);  /* try existing upvalues */
       if (idx < 0) {  /* not found? */
         singlevaraux(fs->prev, n, var, 0);  /* try upper levels */
         if (var->k == VLOCAL || var->k == VUPVAL)  /* local or upvalue? */
           idx  = newupvalue(fs, n, var);  /* will be a new upvalue */
         else  /* it is a global or a constant */
           return;  /* don't need to do anything at this level */
       }
       init_exp(var, VUPVAL, idx);  /* new or old upvalue */
     }
   }
 }
 
 
 /*
 ** Find a variable with the given name 'n', handling global variables
 ** too.
 */
 static void singlevar (LexState *ls, expdesc *var) {
   TString *varname = str_checkname(ls);
   FuncState *fs = ls->fs;
   singlevaraux(fs, varname, var, 1);
   if (var->k == VVOID) {  /* global name? */
     expdesc key;
     singlevaraux(fs, ls->envn, var, 1);  /* get environment variable */
     lua_assert(var->k != VVOID);  /* this one must exist */
     luaK_exp2anyregup(fs, var);  /* but could be a constant */
     codestring(&key, varname);  /* key is variable name */
     luaK_indexed(fs, var, &key);  /* env[varname] */
   }
 }
 
 
 /*
 ** Adjust the number of results from an expression list 'e' with 'nexps'
 ** expressions to 'nvars' values.
 */
 static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e) {
   FuncState *fs = ls->fs;
   int needed = nvars - nexps;  /* extra values needed */
   if (hasmultret(e->k)) {  /* last expression has multiple returns? */
     int extra = needed + 1;  /* discount last expression itself */
     if (extra < 0)
       extra = 0;
     luaK_setreturns(fs, e, extra);  /* last exp. provides the difference */
   }
   else {
     if (e->k != VVOID)  /* at least one expression? */
       luaK_exp2nextreg(fs, e);  /* close last expression */
     if (needed > 0)  /* missing values? */
       luaK_nil(fs, fs->freereg, needed);  /* complete with nils */
   }
   if (needed > 0)
     luaK_reserveregs(fs, needed);  /* registers for extra values */
   else  /* adding 'needed' is actually a subtraction */
     fs->freereg = cast_byte(fs->freereg + needed);  /* remove extra values */
 }
 
 
 #define enterlevel(ls)	luaE_incCstack(ls->L)
 
 
 #define leavelevel(ls) ((ls)->L->nCcalls--)
 
 
 /*
 ** Generates an error that a goto jumps into the scope of some
 ** local variable.
 */
 static l_noret jumpscopeerror (LexState *ls, Labeldesc *gt) {
   TString *tsname = getlocalvardesc(ls->fs, gt->nactvar)->vd.name;
   const char *varname = getstr(tsname);
   const char *msg = "<goto %s> at line %d jumps into the scope of local '%s'";
   msg = luaO_pushfstring(ls->L, msg, getstr(gt->name), gt->line, varname);
   luaK_semerror(ls, msg);  /* raise the error */
 }
 
 
 /*
 ** Closes the goto at index 'g' to given 'label' and removes it
 ** from the list of pending gotos.
 ** If it jumps into the scope of some variable, raises an error.
 ** The goto needs a CLOSE if it jumps out of a block with upvalues,
 ** or out of the scope of some variable and the block has upvalues
 ** (signaled by parameter 'bup').
 */
 static void closegoto (LexState *ls, int g, Labeldesc *label, int bup) {
   int i;
   FuncState *fs = ls->fs;
   Labellist *gl = &ls->dyd->gt;  /* list of gotos */
   Labeldesc *gt = &gl->arr[g];  /* goto to be resolved */
   lua_assert(eqstr(gt->name, label->name));
   if (l_unlikely(gt->nactvar < label->nactvar))  /* enter some scope? */
     jumpscopeerror(ls, gt);
   if (gt->close ||
       (label->nactvar < gt->nactvar && bup)) {  /* needs close? */
     lu_byte stklevel = reglevel(fs, label->nactvar);
     /* move jump to CLOSE position */
     fs->f->code[gt->pc + 1] = fs->f->code[gt->pc];
     /* put CLOSE instruction at original position */
     fs->f->code[gt->pc] = CREATE_ABCk(OP_CLOSE, stklevel, 0, 0, 0);
     gt->pc++;  /* must point to jump instruction */
   }
   luaK_patchlist(ls->fs, gt->pc, label->pc);  /* goto jumps to label */
   for (i = g; i < gl->n - 1; i++)  /* remove goto from pending list */
     gl->arr[i] = gl->arr[i + 1];
   gl->n--;
 }
 
 
 /*
 ** Search for an active label with the given name, starting at
 ** index 'ilb' (so that it can searh for all labels in current block
 ** or all labels in current function).
 */
 static Labeldesc *findlabel (LexState *ls, TString *name, int ilb) {
   Dyndata *dyd = ls->dyd;
   for (; ilb < dyd->label.n; ilb++) {
     Labeldesc *lb = &dyd->label.arr[ilb];
     if (eqstr(lb->name, name))  /* correct label? */
       return lb;
   }
   return NULL;  /* label not found */
 }
 
 
 /*
 ** Adds a new label/goto in the corresponding list.
 */
 static int newlabelentry (LexState *ls, Labellist *l, TString *name,
                           int line, int pc) {
   int n = l->n;
   luaM_growvector(ls->L, l->arr, n, l->size,
                   Labeldesc, SHRT_MAX, "labels/gotos");
   l->arr[n].name = name;
   l->arr[n].line = line;
   l->arr[n].nactvar = ls->fs->nactvar;
   l->arr[n].close = 0;
   l->arr[n].pc = pc;
   l->n = n + 1;
   return n;
 }
 
 
 /*
 ** Create an entry for the goto and the code for it. As it is not known
 ** at this point whether the goto may need a CLOSE, the code has a jump
 ** followed by an CLOSE. (As the CLOSE comes after the jump, it is a
 ** dead instruction; it works as a placeholder.) When the goto is closed
 ** against a label, if it needs a CLOSE, the two instructions swap
 ** positions, so that the CLOSE comes before the jump.
 */
 static int newgotoentry (LexState *ls, TString *name, int line) {
   FuncState *fs = ls->fs;
   int pc = luaK_jump(fs);  /* create jump */
   luaK_codeABC(fs, OP_CLOSE, 0, 1, 0);  /* spaceholder, marked as dead */
   return newlabelentry(ls, &ls->dyd->gt, name, line, pc);
 }
 
 
 /*
 ** Create a new label with the given 'name' at the given 'line'.
 ** 'last' tells whether label is the last non-op statement in its
 ** block. Solves all pending gotos to this new label and adds
 ** a close instruction if necessary.
 ** Returns true iff it added a close instruction.
 */
 static void createlabel (LexState *ls, TString *name, int line, int last) {
   FuncState *fs = ls->fs;
   Labellist *ll = &ls->dyd->label;
   int l = newlabelentry(ls, ll, name, line, luaK_getlabel(fs));
   if (last) {  /* label is last no-op statement in the block? */
     /* assume that locals are already out of scope */
     ll->arr[l].nactvar = fs->bl->nactvar;
   }
 }
 
 
 /*
 ** Traverse the pending goto's of the finishing block checking whether
 ** each match some label of that block. Those that do not match are
 ** "exported" to the outer block, to be solved there. In particular,
 ** its 'nactvar' is updated with the level of the inner block,
 ** as the variables of the inner block are now out of scope.
 */
 static void solvegotos (FuncState *fs, BlockCnt *bl) {
   LexState *ls = fs->ls;
   Labellist *gl = &ls->dyd->gt;
   int outlevel = reglevel(fs, bl->nactvar);  /* level outside the block */
   int igt = bl->firstgoto;  /* first goto in the finishing block */
   while (igt < gl->n) {   /* for each pending goto */
     Labeldesc *gt = &gl->arr[igt];
     /* search for a matching label in the current block */
     Labeldesc *lb = findlabel(ls, gt->name, bl->firstlabel);
     if (lb != NULL)  /* found a match? */
       closegoto(ls, igt, lb, bl->upval);  /* close and remove goto */
     else {  /* adjust 'goto' for outer block */
       /* block has variables to be closed and goto escapes the scope of
          some variable? */
       if (bl->upval && reglevel(fs, gt->nactvar) > outlevel)
         gt->close = 1;  /* jump may need a close */
       gt->nactvar = bl->nactvar;  /* correct level for outer block */
       igt++;  /* go to next goto */
     }
   }
   ls->dyd->label.n = bl->firstlabel;  /* remove local labels */
 }
 
 
 static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isloop) {
   bl->isloop = isloop;
   bl->nactvar = fs->nactvar;
   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 == luaY_nvarstack(fs));
 }
 
 
 /*
 ** generates an error for an undefined 'goto'.
 */
 static l_noret undefgoto (LexState *ls, Labeldesc *gt) {
   const char *msg = "no visible label '%s' for <goto> at line %d";
   msg = luaO_pushfstring(ls->L, msg, getstr(gt->name), gt->line);
   /* breaks are checked when created, cannot be undefined */
   lua_assert(!eqstr(gt->name, luaS_newliteral(ls->L, "break")));
   luaK_semerror(ls, msg);
 }
 
 
 static void leaveblock (FuncState *fs) {
   BlockCnt *bl = fs->bl;
   LexState *ls = fs->ls;
   lu_byte stklevel = reglevel(fs, bl->nactvar);  /* level outside block */
   if (bl->previous && bl->upval)  /* need a 'close'? */
     luaK_codeABC(fs, OP_CLOSE, stklevel, 0, 0);
   fs->freereg = stklevel;  /* free registers */
   removevars(fs, bl->nactvar);  /* remove block locals */
   lua_assert(bl->nactvar == fs->nactvar);  /* back to level on entry */
   if (bl->isloop == 2)  /* has to fix pending breaks? */
     createlabel(ls, luaS_newliteral(ls->L, "break"), 0, 0);
   solvegotos(fs, bl);
   if (bl->previous == NULL) {  /* was it the last block? */
     if (bl->firstgoto < ls->dyd->gt.n)  /* still pending gotos? */
       undefgoto(ls, &ls->dyd->gt.arr[bl->firstgoto]);  /* error */
   }
   fs->bl = bl->previous;  /* current block now is previous one */
 }
 
 
 /*
 ** adds a new prototype into list of prototypes
 */
 static Proto *addprototype (LexState *ls) {
   Proto *clp;
   lua_State *L = ls->L;
   FuncState *fs = ls->fs;
   Proto *f = fs->f;  /* prototype of current function */
   if (fs->np >= f->sizep) {
     int oldsize = f->sizep;
     luaM_growvector(L, f->p, fs->np, f->sizep, Proto *, MAXARG_Bx, "functions");
     while (oldsize < f->sizep)
       f->p[oldsize++] = NULL;
   }
   f->p[fs->np++] = clp = luaF_newproto(L);
   luaC_objbarrier(L, f, clp);
   return clp;
 }
 
 
 /*
 ** codes instruction to create new closure in parent function.
 ** The OP_CLOSURE instruction uses the last available register,
 ** so that, if it invokes the GC, the GC knows which registers
 ** are in use at that time.
 
 */
 static void codeclosure (LexState *ls, expdesc *v) {
   FuncState *fs = ls->fs->prev;
   init_exp(v, VRELOC, luaK_codeABx(fs, OP_CLOSURE, 0, fs->np - 1));
   luaK_exp2nextreg(fs, v);  /* fix it at the last register */
 }
 
 
 static void open_func (LexState *ls, FuncState *fs, BlockCnt *bl) {
   lua_State *L = ls->L;
   Proto *f = fs->f;
   fs->prev = ls->fs;  /* linked list of funcstates */
   fs->ls = ls;
   ls->fs = fs;
   fs->pc = 0;
   fs->previousline = f->linedefined;
   fs->iwthabs = 0;
   fs->lasttarget = 0;
   fs->freereg = 0;
   fs->nk = 0;
   fs->nabslineinfo = 0;
   fs->np = 0;
   fs->nups = 0;
   fs->ndebugvars = 0;
   fs->nactvar = 0;
   fs->needclose = 0;
   fs->firstlocal = ls->dyd->actvar.n;
   fs->firstlabel = ls->dyd->label.n;
   fs->bl = NULL;
   f->source = ls->source;
   luaC_objbarrier(L, f, f->source);
   f->maxstacksize = 2;  /* registers 0/1 are always valid */
   fs->kcache = luaH_new(L);  /* create table for function */
   sethvalue2s(L, L->top.p, fs->kcache);  /* anchor it */
   luaD_inctop(L);
   enterblock(fs, bl, 0);
 }
 
 
 static void close_func (LexState *ls) {
   lua_State *L = ls->L;
   FuncState *fs = ls->fs;
   Proto *f = fs->f;
   luaK_ret(fs, luaY_nvarstack(fs), 0);  /* final return */
   leaveblock(fs);
   lua_assert(fs->bl == NULL);
   luaK_finish(fs);
   luaM_shrinkvector(L, f->code, f->sizecode, fs->pc, Instruction);
   luaM_shrinkvector(L, f->lineinfo, f->sizelineinfo, fs->pc, ls_byte);
   luaM_shrinkvector(L, f->abslineinfo, f->sizeabslineinfo,
                        fs->nabslineinfo, AbsLineInfo);
   luaM_shrinkvector(L, f->k, f->sizek, fs->nk, TValue);
   luaM_shrinkvector(L, f->p, f->sizep, fs->np, Proto *);
   luaM_shrinkvector(L, f->locvars, f->sizelocvars, fs->ndebugvars, LocVar);
   luaM_shrinkvector(L, f->upvalues, f->sizeupvalues, fs->nups, Upvaldesc);
   ls->fs = fs->prev;
   L->top.p--;  /* pop kcache table */
   luaC_checkGC(L);
 }
 
 
 /*
 ** {======================================================================
 ** GRAMMAR RULES
 ** =======================================================================
 */
 
 
 /*
 ** check whether current token is in the follow set of a block.
 ** 'until' closes syntactical blocks, but do not close scope,
 ** so it is handled in separate.
 */
 static int block_follow (LexState *ls, int withuntil) {
   switch (ls->t.token) {
     case TK_ELSE: case TK_ELSEIF:
     case TK_END: case TK_EOS:
       return 1;
     case TK_UNTIL: return withuntil;
     default: return 0;
   }
 }
 
 
 static void statlist (LexState *ls) {
   /* statlist -> { stat [';'] } */
   while (!block_follow(ls, 1)) {
     if (ls->t.token == TK_RETURN) {
       statement(ls);
       return;  /* 'return' must be last statement */
     }
     statement(ls);
   }
 }
 
 
 static void fieldsel (LexState *ls, expdesc *v) {
   /* fieldsel -> ['.' | ':'] NAME */
   FuncState *fs = ls->fs;
   expdesc key;
   luaK_exp2anyregup(fs, v);
   luaX_next(ls);  /* skip the dot or colon */
   codename(ls, &key);
   luaK_indexed(fs, v, &key);
 }
 
 
 static void yindex (LexState *ls, expdesc *v) {
   /* index -> '[' expr ']' */
   luaX_next(ls);  /* skip the '[' */
   expr(ls, v);
   luaK_exp2val(ls->fs, v);
   checknext(ls, ']');
 }
 
 
 /*
 ** {======================================================================
 ** Rules for Constructors
 ** =======================================================================
 */
 
 typedef struct ConsControl {
   expdesc v;  /* last list item read */
   expdesc *t;  /* table descriptor */
   int nh;  /* total number of 'record' elements */
   int na;  /* number of array elements already stored */
   int tostore;  /* number of array elements pending to be stored */
   int maxtostore;  /* maximum number of pending elements */
 } ConsControl;
 
 
 static void recfield (LexState *ls, ConsControl *cc) {
   /* recfield -> (NAME | '['exp']') = exp */
   FuncState *fs = ls->fs;
   lu_byte reg = ls->fs->freereg;
   expdesc tab, key, val;
   if (ls->t.token == TK_NAME) {
     luaY_checklimit(fs, cc->nh, INT_MAX / 2, "items in a constructor");
     codename(ls, &key);
   }
   else  /* ls->t.token == '[' */
     yindex(ls, &key);
   cc->nh++;
   checknext(ls, '=');
   tab = *cc->t;
   luaK_indexed(fs, &tab, &key);
   expr(ls, &val);
   luaK_storevar(fs, &tab, &val);
   fs->freereg = reg;  /* free registers */
 }
 
 
 static void closelistfield (FuncState *fs, ConsControl *cc) {
   if (cc->v.k == VVOID) return;  /* there is no list item */
   luaK_exp2nextreg(fs, &cc->v);
   cc->v.k = VVOID;
   if (cc->tostore >= cc->maxtostore) {
     luaK_setlist(fs, cc->t->u.info, cc->na, cc->tostore);  /* flush */
     cc->na += cc->tostore;
     cc->tostore = 0;  /* no more items pending */
   }
 }
 
 
 static void lastlistfield (FuncState *fs, ConsControl *cc) {
   if (cc->tostore == 0) return;
   if (hasmultret(cc->v.k)) {
     luaK_setmultret(fs, &cc->v);
     luaK_setlist(fs, cc->t->u.info, cc->na, LUA_MULTRET);
     cc->na--;  /* do not count last expression (unknown number of elements) */
   }
   else {
     if (cc->v.k != VVOID)
       luaK_exp2nextreg(fs, &cc->v);
     luaK_setlist(fs, cc->t->u.info, cc->na, cc->tostore);
   }
   cc->na += cc->tostore;
 }
 
 
 static void listfield (LexState *ls, ConsControl *cc) {
   /* listfield -> exp */
   expr(ls, &cc->v);
   cc->tostore++;
 }
 
 
 static void field (LexState *ls, ConsControl *cc) {
   /* field -> listfield | recfield */
   switch(ls->t.token) {
     case TK_NAME: {  /* may be 'listfield' or 'recfield' */
       if (luaX_lookahead(ls) != '=')  /* expression? */
         listfield(ls, cc);
       else
         recfield(ls, cc);
       break;
     }
     case '[': {
       recfield(ls, cc);
       break;
     }
     default: {
       listfield(ls, cc);
       break;
     }
   }
 }
 
 
 /*
 ** Compute a limit for how many registers a constructor can use before
 ** emitting a 'SETLIST' instruction, based on how many registers are
 ** available.
 */
 static int maxtostore (FuncState *fs) {
   int numfreeregs = MAX_FSTACK - fs->freereg;
   if (numfreeregs >= 160)  /* "lots" of registers? */
     return numfreeregs / 5;  /* use up to 1/5 of them */
   else if (numfreeregs >= 80)  /* still "enough" registers? */
     return 10;  /* one 'SETLIST' instruction for each 10 values */
   else  /* save registers for potential more nesting */
     return 1;
 }
 
 
 static void constructor (LexState *ls, expdesc *t) {
   /* constructor -> '{' [ field { sep field } [sep] ] '}'
      sep -> ',' | ';' */
   FuncState *fs = ls->fs;
   int line = ls->linenumber;
   int pc = luaK_codevABCk(fs, OP_NEWTABLE, 0, 0, 0, 0);
   ConsControl cc;
   luaK_code(fs, 0);  /* space for extra arg. */
   cc.na = cc.nh = cc.tostore = 0;
   cc.t = t;
   init_exp(t, VNONRELOC, fs->freereg);  /* table will be at stack top */
   luaK_reserveregs(fs, 1);
   init_exp(&cc.v, VVOID, 0);  /* no value (yet) */
   checknext(ls, '{' /*}*/);
   cc.maxtostore = maxtostore(fs);
   do {
     lua_assert(cc.v.k == VVOID || cc.tostore > 0);
     if (ls->t.token == /*{*/ '}') break;
     closelistfield(fs, &cc);
     field(ls, &cc);
   } while (testnext(ls, ',') || testnext(ls, ';'));
   check_match(ls, /*{*/ '}', '{' /*}*/, line);
   lastlistfield(fs, &cc);
   luaK_settablesize(fs, pc, t->u.info, cc.na, cc.nh);
 }
 
 /* }====================================================================== */
 
 
 static void setvararg (FuncState *fs, int nparams) {
   fs->f->flag |= PF_ISVARARG;
   luaK_codeABC(fs, OP_VARARGPREP, nparams, 0, 0);
 }
 
 
 static void parlist (LexState *ls) {
   /* parlist -> [ {NAME ','} (NAME | '...') ] */
   FuncState *fs = ls->fs;
   Proto *f = fs->f;
   int nparams = 0;
   int isvararg = 0;
   if (ls->t.token != ')') {  /* is 'parlist' not empty? */
     do {
       switch (ls->t.token) {
         case TK_NAME: {
           new_localvar(ls, str_checkname(ls));
           nparams++;
           break;
         }
         case TK_DOTS: {
           luaX_next(ls);
           isvararg = 1;
           break;
         }
         default: luaX_syntaxerror(ls, "<name> or '...' expected");
       }
     } while (!isvararg && testnext(ls, ','));
   }
   adjustlocalvars(ls, nparams);
   f->numparams = cast_byte(fs->nactvar);
   if (isvararg)
     setvararg(fs, f->numparams);  /* declared vararg */
   luaK_reserveregs(fs, fs->nactvar);  /* reserve registers for parameters */
 }
 
 
 static void body (LexState *ls, expdesc *e, int ismethod, int line) {
   /* body ->  '(' parlist ')' block END */
   FuncState new_fs;
   BlockCnt bl;
   new_fs.f = addprototype(ls);
   new_fs.f->linedefined = line;
   open_func(ls, &new_fs, &bl);
   checknext(ls, '(');
   if (ismethod) {
     new_localvarliteral(ls, "self");  /* create 'self' parameter */
     adjustlocalvars(ls, 1);
   }
   parlist(ls);
   checknext(ls, ')');
   statlist(ls);
   new_fs.f->lastlinedefined = ls->linenumber;
   check_match(ls, TK_END, TK_FUNCTION, line);
   codeclosure(ls, e);
   close_func(ls);
 }
 
 
 static int explist (LexState *ls, expdesc *v) {
   /* explist -> expr { ',' expr } */
   int n = 1;  /* at least one expression */
   expr(ls, v);
   while (testnext(ls, ',')) {
     luaK_exp2nextreg(ls->fs, v);
     expr(ls, v);
     n++;
   }
   return n;
 }
 
 
 static void funcargs (LexState *ls, expdesc *f) {
   FuncState *fs = ls->fs;
   expdesc args;
   int base, nparams;
   int line = ls->linenumber;
   switch (ls->t.token) {
     case '(': {  /* funcargs -> '(' [ explist ] ')' */
       luaX_next(ls);
       if (ls->t.token == ')')  /* arg list is empty? */
         args.k = VVOID;
       else {
         explist(ls, &args);
         if (hasmultret(args.k))
           luaK_setmultret(fs, &args);
       }
       check_match(ls, ')', '(', line);
       break;
     }
     case '{' /*}*/: {  /* funcargs -> constructor */
       constructor(ls, &args);
       break;
     }
     case TK_STRING: {  /* funcargs -> STRING */
       codestring(&args, ls->t.seminfo.ts);
       luaX_next(ls);  /* must use 'seminfo' before 'next' */
       break;
     }
     default: {
       luaX_syntaxerror(ls, "function arguments expected");
     }
   }
   lua_assert(f->k == VNONRELOC);
   base = f->u.info;  /* base register for call */
   if (hasmultret(args.k))
     nparams = LUA_MULTRET;  /* open call */
   else {
     if (args.k != VVOID)
       luaK_exp2nextreg(fs, &args);  /* close last argument */
     nparams = fs->freereg - (base+1);
   }
   init_exp(f, VCALL, luaK_codeABC(fs, OP_CALL, base, nparams+1, 2));
   luaK_fixline(fs, line);
   /* call removes function and arguments and leaves one result (unless
      changed later) */
   fs->freereg = cast_byte(base + 1);
 }
 
 
 
 
 /*
 ** {======================================================================
 ** Expression parsing
 ** =======================================================================
 */
 
 
 static void primaryexp (LexState *ls, expdesc *v) {
   /* primaryexp -> NAME | '(' expr ')' */
   switch (ls->t.token) {
     case '(': {
       int line = ls->linenumber;
       luaX_next(ls);
       expr(ls, v);
       check_match(ls, ')', '(', line);
       luaK_dischargevars(ls->fs, v);
       return;
     }
     case TK_NAME: {
       singlevar(ls, v);
       return;
     }
     default: {
       luaX_syntaxerror(ls, "unexpected symbol");
     }
   }
 }
 
 
 static void suffixedexp (LexState *ls, expdesc *v) {
   /* suffixedexp ->
        primaryexp { '.' NAME | '[' exp ']' | ':' NAME funcargs | funcargs } */
   FuncState *fs = ls->fs;
   primaryexp(ls, v);
   for (;;) {
     switch (ls->t.token) {
       case '.': {  /* fieldsel */
         fieldsel(ls, v);
         break;
       }
       case '[': {  /* '[' exp ']' */
         expdesc key;
         luaK_exp2anyregup(fs, v);
         yindex(ls, &key);
         luaK_indexed(fs, v, &key);
         break;
       }
       case ':': {  /* ':' NAME funcargs */
         expdesc key;
         luaX_next(ls);
         codename(ls, &key);
         luaK_self(fs, v, &key);
         funcargs(ls, v);
         break;
       }
       case '(': case TK_STRING: case '{' /*}*/: {  /* funcargs */
         luaK_exp2nextreg(fs, v);
         funcargs(ls, v);
         break;
       }
       default: return;
     }
   }
 }
 
 
 static void simpleexp (LexState *ls, expdesc *v) {
   /* simpleexp -> FLT | INT | STRING | NIL | TRUE | FALSE | ... |
                   constructor | FUNCTION body | suffixedexp */
   switch (ls->t.token) {
     case TK_FLT: {
       init_exp(v, VKFLT, 0);
       v->u.nval = ls->t.seminfo.r;
       break;
     }
     case TK_INT: {
       init_exp(v, VKINT, 0);
       v->u.ival = ls->t.seminfo.i;
       break;
     }
     case TK_STRING: {
       codestring(v, ls->t.seminfo.ts);
       break;
     }
     case TK_NIL: {
       init_exp(v, VNIL, 0);
       break;
     }
     case TK_TRUE: {
       init_exp(v, VTRUE, 0);
       break;
     }
     case TK_FALSE: {
       init_exp(v, VFALSE, 0);
       break;
     }
     case TK_DOTS: {  /* vararg */
       FuncState *fs = ls->fs;
       check_condition(ls, fs->f->flag & PF_ISVARARG,
                       "cannot use '...' outside a vararg function");
       init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 0, 1));
       break;
     }
     case '{' /*}*/: {  /* constructor */
       constructor(ls, v);
       return;
     }
     case TK_FUNCTION: {
       luaX_next(ls);
       body(ls, v, 0, ls->linenumber);
       return;
     }
     default: {
       suffixedexp(ls, v);
       return;
     }
   }
   luaX_next(ls);
 }
 
 
 static UnOpr getunopr (int op) {
   switch (op) {
     case TK_NOT: return OPR_NOT;
     case '-': return OPR_MINUS;
     case '~': return OPR_BNOT;
     case '#': return OPR_LEN;
     default: return OPR_NOUNOPR;
   }
 }
 
 
 static BinOpr getbinopr (int op) {
   switch (op) {
     case '+': return OPR_ADD;
     case '-': return OPR_SUB;
     case '*': return OPR_MUL;
     case '%': return OPR_MOD;
     case '^': return OPR_POW;
     case '/': return OPR_DIV;
     case TK_IDIV: return OPR_IDIV;
     case '&': return OPR_BAND;
     case '|': return OPR_BOR;
     case '~': return OPR_BXOR;
     case TK_SHL: return OPR_SHL;
     case TK_SHR: return OPR_SHR;
     case TK_CONCAT: return OPR_CONCAT;
     case TK_NE: return OPR_NE;
     case TK_EQ: return OPR_EQ;
     case '<': return OPR_LT;
     case TK_LE: return OPR_LE;
     case '>': return OPR_GT;
     case TK_GE: return OPR_GE;
     case TK_AND: return OPR_AND;
     case TK_OR: return OPR_OR;
     default: return OPR_NOBINOPR;
   }
 }
 
 
 /*
 ** Priority table for binary operators.
 */
 static const struct {
   lu_byte left;  /* left priority for each binary operator */
   lu_byte right; /* right priority */
 } priority[] = {  /* ORDER OPR */
    {10, 10}, {10, 10},           /* '+' '-' */
    {11, 11}, {11, 11},           /* '*' '%' */
    {14, 13},                  /* '^' (right associative) */
    {11, 11}, {11, 11},           /* '/' '//' */
    {6, 6}, {4, 4}, {5, 5},   /* '&' '|' '~' */
    {7, 7}, {7, 7},           /* '<<' '>>' */
    {9, 8},                   /* '..' (right associative) */
    {3, 3}, {3, 3}, {3, 3},   /* ==, <, <= */
    {3, 3}, {3, 3}, {3, 3},   /* ~=, >, >= */
    {2, 2}, {1, 1}            /* and, or */
 };
 
 #define UNARY_PRIORITY	12  /* priority for unary operators */
 
 
 /*
 ** subexpr -> (simpleexp | unop subexpr) { binop subexpr }
 ** where 'binop' is any binary operator with a priority higher than 'limit'
 */
 static BinOpr subexpr (LexState *ls, expdesc *v, int limit) {
   BinOpr op;
   UnOpr uop;
   enterlevel(ls);
   uop = getunopr(ls->t.token);
   if (uop != OPR_NOUNOPR) {  /* prefix (unary) operator? */
     int line = ls->linenumber;
     luaX_next(ls);  /* skip operator */
     subexpr(ls, v, UNARY_PRIORITY);
     luaK_prefix(ls->fs, uop, v, line);
   }
   else simpleexp(ls, v);
   /* expand while operators have priorities higher than 'limit' */
   op = getbinopr(ls->t.token);
   while (op != OPR_NOBINOPR && priority[op].left > limit) {
     expdesc v2;
     BinOpr nextop;
     int line = ls->linenumber;
     luaX_next(ls);  /* skip operator */
     luaK_infix(ls->fs, op, v);
     /* read sub-expression with higher priority */
     nextop = subexpr(ls, &v2, priority[op].right);
     luaK_posfix(ls->fs, op, v, &v2, line);
     op = nextop;
   }
   leavelevel(ls);
   return op;  /* return first untreated operator */
 }
 
 
 static void expr (LexState *ls, expdesc *v) {
   subexpr(ls, v, 0);
 }
 
 /* }==================================================================== */
 
 
 
 /*
 ** {======================================================================
 ** Rules for Statements
 ** =======================================================================
 */
 
 
 static void block (LexState *ls) {
   /* block -> statlist */
   FuncState *fs = ls->fs;
   BlockCnt bl;
   enterblock(fs, &bl, 0);
   statlist(ls);
   leaveblock(fs);
 }
 
 
 /*
 ** structure to chain all variables in the left-hand side of an
 ** assignment
 */
 struct LHS_assign {
   struct LHS_assign *prev;
   expdesc v;  /* variable (global, local, upvalue, or indexed) */
 };
 
 
 /*
 ** check whether, in an assignment to an upvalue/local variable, the
 ** upvalue/local variable is begin used in a previous assignment to a
 ** table. If so, save original upvalue/local value in a safe place and
 ** use this safe copy in the previous assignment.
 */
 static void check_conflict (LexState *ls, struct LHS_assign *lh, expdesc *v) {
   FuncState *fs = ls->fs;
   lu_byte extra = fs->freereg;  /* eventual position to save local variable */
   int conflict = 0;
   for (; lh; lh = lh->prev) {  /* check all previous assignments */
     if (vkisindexed(lh->v.k)) {  /* assignment to table field? */
       if (lh->v.k == VINDEXUP) {  /* is table an upvalue? */
         if (v->k == VUPVAL && lh->v.u.ind.t == v->u.info) {
           conflict = 1;  /* table is the upvalue being assigned now */
           lh->v.k = VINDEXSTR;
           lh->v.u.ind.t = extra;  /* assignment will use safe copy */
         }
       }
       else {  /* table is a register */
         if (v->k == VLOCAL && lh->v.u.ind.t == v->u.var.ridx) {
           conflict = 1;  /* table is the local being assigned now */
           lh->v.u.ind.t = extra;  /* assignment will use safe copy */
         }
         /* is index the local being assigned? */
         if (lh->v.k == VINDEXED && v->k == VLOCAL &&
             lh->v.u.ind.idx == v->u.var.ridx) {
           conflict = 1;
           lh->v.u.ind.idx = extra;  /* previous assignment will use safe copy */
         }
       }
     }
   }
   if (conflict) {
     /* copy upvalue/local value to a temporary (in position 'extra') */
     if (v->k == VLOCAL)
       luaK_codeABC(fs, OP_MOVE, extra, v->u.var.ridx, 0);
     else
       luaK_codeABC(fs, OP_GETUPVAL, extra, v->u.info, 0);
     luaK_reserveregs(fs, 1);
   }
 }
 
 /*
 ** Parse and compile a multiple assignment. The first "variable"
 ** (a 'suffixedexp') was already read by the caller.
 **
 ** assignment -> suffixedexp restassign
 ** restassign -> ',' suffixedexp restassign | '=' explist
 */
 static void restassign (LexState *ls, struct LHS_assign *lh, int nvars) {
   expdesc e;
   check_condition(ls, vkisvar(lh->v.k), "syntax error");
   check_readonly(ls, &lh->v);
   if (testnext(ls, ',')) {  /* restassign -> ',' suffixedexp restassign */
     struct LHS_assign nv;
     nv.prev = lh;
     suffixedexp(ls, &nv.v);
     if (!vkisindexed(nv.v.k))
       check_conflict(ls, lh, &nv.v);
     enterlevel(ls);  /* control recursion depth */
     restassign(ls, &nv, nvars+1);
     leavelevel(ls);
   }
   else {  /* restassign -> '=' explist */
     int nexps;
     checknext(ls, '=');
     nexps = explist(ls, &e);
     if (nexps != nvars)
       adjust_assign(ls, nvars, nexps, &e);
     else {
       luaK_setoneret(ls->fs, &e);  /* close last expression */
       luaK_storevar(ls->fs, &lh->v, &e);
       return;  /* avoid default */
     }
   }
   init_exp(&e, VNONRELOC, ls->fs->freereg-1);  /* default assignment */
   luaK_storevar(ls->fs, &lh->v, &e);
 }
 
 
 static int cond (LexState *ls) {
   /* cond -> exp */
   expdesc v;
   expr(ls, &v);  /* read condition */
   if (v.k == VNIL) v.k = VFALSE;  /* 'falses' are all equal here */
   luaK_goiftrue(ls->fs, &v);
   return v.f;
 }
 
 
 static void gotostat (LexState *ls, int line) {
   TString *name = str_checkname(ls);  /* label's name */
   newgotoentry(ls, name, line);
 }
 
 
 /*
 ** Break statement. Semantically equivalent to "goto break".
 */
 static void breakstat (LexState *ls, int line) {
   BlockCnt *bl;  /* to look for an enclosing loop */
   for (bl = ls->fs->bl; bl != NULL; bl = bl->previous) {
     if (bl->isloop)  /* found one? */
       goto ok;
   }
   luaX_syntaxerror(ls, "break outside loop");
  ok:
   bl->isloop = 2;  /* signal that block has pending breaks */
   luaX_next(ls);  /* skip break */
   newgotoentry(ls, luaS_newliteral(ls->L, "break"), line);
 }
 
 
 /*
 ** Check whether there is already a label with the given 'name' at
 ** current function.
 */
 static void checkrepeated (LexState *ls, TString *name) {
   Labeldesc *lb = findlabel(ls, name, ls->fs->firstlabel);
   if (l_unlikely(lb != NULL)) {  /* already defined? */
     const char *msg = "label '%s' already defined on line %d";
     msg = luaO_pushfstring(ls->L, msg, getstr(name), lb->line);
     luaK_semerror(ls, msg);  /* error */
   }
 }
 
 
 static void labelstat (LexState *ls, TString *name, int line) {
   /* label -> '::' NAME '::' */
   checknext(ls, TK_DBCOLON);  /* skip double colon */
   while (ls->t.token == ';' || ls->t.token == TK_DBCOLON)
     statement(ls);  /* skip other no-op statements */
   checkrepeated(ls, name);  /* check for repeated labels */
   createlabel(ls, name, line, block_follow(ls, 0));
 }
 
 
 static void whilestat (LexState *ls, int line) {
   /* whilestat -> WHILE cond DO block END */
   FuncState *fs = ls->fs;
   int whileinit;
   int condexit;
   BlockCnt bl;
   luaX_next(ls);  /* skip WHILE */
   whileinit = luaK_getlabel(fs);
   condexit = cond(ls);
   enterblock(fs, &bl, 1);
   checknext(ls, TK_DO);
   block(ls);
   luaK_jumpto(fs, whileinit);
   check_match(ls, TK_END, TK_WHILE, line);
   leaveblock(fs);
   luaK_patchtohere(fs, condexit);  /* false conditions finish the loop */
 }
 
 
 static void repeatstat (LexState *ls, int line) {
   /* repeatstat -> REPEAT block UNTIL cond */
   int condexit;
   FuncState *fs = ls->fs;
   int repeat_init = luaK_getlabel(fs);
   BlockCnt bl1, bl2;
   enterblock(fs, &bl1, 1);  /* loop block */
   enterblock(fs, &bl2, 0);  /* scope block */
   luaX_next(ls);  /* skip REPEAT */
   statlist(ls);
   check_match(ls, TK_UNTIL, TK_REPEAT, line);
   condexit = cond(ls);  /* read condition (inside scope block) */
   leaveblock(fs);  /* finish scope */
   if (bl2.upval) {  /* upvalues? */
     int exit = luaK_jump(fs);  /* normal exit must jump over fix */
     luaK_patchtohere(fs, condexit);  /* repetition must close upvalues */
     luaK_codeABC(fs, OP_CLOSE, reglevel(fs, bl2.nactvar), 0, 0);
     condexit = luaK_jump(fs);  /* repeat after closing upvalues */
     luaK_patchtohere(fs, exit);  /* normal exit comes to here */
   }
   luaK_patchlist(fs, condexit, repeat_init);  /* close the loop */
   leaveblock(fs);  /* finish loop */
 }
 
 
 /*
 ** Read an expression and generate code to put its results in next
 ** stack slot.
 **
 */
 static void exp1 (LexState *ls) {
   expdesc e;
   expr(ls, &e);
   luaK_exp2nextreg(ls->fs, &e);
   lua_assert(e.k == VNONRELOC);
 }
 
 
 /*
 ** Fix for instruction at position 'pc' to jump to 'dest'.
 ** (Jump addresses are relative in Lua). 'back' true means
 ** a back jump.
 */
 static void fixforjump (FuncState *fs, int pc, int dest, int back) {
   Instruction *jmp = &fs->f->code[pc];
   int offset = dest - (pc + 1);
   if (back)
     offset = -offset;
   if (l_unlikely(offset > MAXARG_Bx))
     luaX_syntaxerror(fs->ls, "control structure too long");
   SETARG_Bx(*jmp, offset);
 }
 
 
 /*
 ** Generate code for a 'for' loop.
 */
 static void forbody (LexState *ls, int base, int line, int nvars, int isgen) {
   /* forbody -> DO block */
   static const OpCode forprep[2] = {OP_FORPREP, OP_TFORPREP};
   static const OpCode forloop[2] = {OP_FORLOOP, OP_TFORLOOP};
   BlockCnt bl;
   FuncState *fs = ls->fs;
   int prep, endfor;
   checknext(ls, TK_DO);
   prep = luaK_codeABx(fs, forprep[isgen], base, 0);
   fs->freereg--;  /* both 'forprep' remove one register from the stack */
   enterblock(fs, &bl, 0);  /* scope for declared variables */
   adjustlocalvars(ls, nvars);
   luaK_reserveregs(fs, nvars);
   block(ls);
   leaveblock(fs);  /* end of scope for declared variables */
   fixforjump(fs, prep, luaK_getlabel(fs), 0);
   if (isgen) {  /* generic for? */
     luaK_codeABC(fs, OP_TFORCALL, base, 0, nvars);
     luaK_fixline(fs, line);
   }
   endfor = luaK_codeABx(fs, forloop[isgen], base, 0);
   fixforjump(fs, endfor, prep + 1, 1);
   luaK_fixline(fs, line);
 }
 
 
 static void fornum (LexState *ls, TString *varname, int line) {
   /* fornum -> NAME = exp,exp[,exp] forbody */
   FuncState *fs = ls->fs;
   int base = fs->freereg;
   new_localvarliteral(ls, "(for state)");
   new_localvarliteral(ls, "(for state)");
   new_localvarkind(ls, varname, RDKCONST);  /* control variable */
   checknext(ls, '=');
   exp1(ls);  /* initial value */
   checknext(ls, ',');
   exp1(ls);  /* limit */
   if (testnext(ls, ','))
     exp1(ls);  /* optional step */
   else {  /* default step = 1 */
     luaK_int(fs, fs->freereg, 1);
     luaK_reserveregs(fs, 1);
   }
   adjustlocalvars(ls, 2);  /* start scope for internal variables */
   forbody(ls, base, line, 1, 0);
 }
 
 
 static void forlist (LexState *ls, TString *indexname) {
   /* forlist -> NAME {,NAME} IN explist forbody */
   FuncState *fs = ls->fs;
   expdesc e;
   int nvars = 4;  /* function, state, closing, control */
   int line;
   int base = fs->freereg;
   /* create internal variables */
   new_localvarliteral(ls, "(for state)");  /* iterator function */
   new_localvarliteral(ls, "(for state)");  /* state */
   new_localvarliteral(ls, "(for state)");  /* closing var. (after swap) */
   new_localvarkind(ls, indexname, RDKCONST);  /* control variable */
   /* other declared variables */
   while (testnext(ls, ',')) {
     new_localvar(ls, str_checkname(ls));
     nvars++;
   }
   checknext(ls, TK_IN);
   line = ls->linenumber;
   adjust_assign(ls, 4, explist(ls, &e), &e);
   adjustlocalvars(ls, 3);  /* start scope for internal variables */
   marktobeclosed(fs);  /* last internal var. must be closed */
   luaK_checkstack(fs, 2);  /* extra space to call iterator */
   forbody(ls, base, line, nvars - 3, 1);
 }
 
 
 static void forstat (LexState *ls, int line) {
   /* forstat -> FOR (fornum | forlist) END */
   FuncState *fs = ls->fs;
   TString *varname;
   BlockCnt bl;
   enterblock(fs, &bl, 1);  /* scope for loop and control variables */
   luaX_next(ls);  /* skip 'for' */
   varname = str_checkname(ls);  /* first variable name */
   switch (ls->t.token) {
     case '=': fornum(ls, varname, line); break;
     case ',': case TK_IN: forlist(ls, varname); break;
     default: luaX_syntaxerror(ls, "'=' or 'in' expected");
   }
   check_match(ls, TK_END, TK_FOR, line);
   leaveblock(fs);  /* loop scope ('break' jumps to this point) */
 }
 
 
 static void test_then_block (LexState *ls, int *escapelist) {
   /* test_then_block -> [IF | ELSEIF] cond THEN block */
   FuncState *fs = ls->fs;
   int condtrue;
   luaX_next(ls);  /* skip IF or ELSEIF */
   condtrue = cond(ls);  /* read condition */
   checknext(ls, TK_THEN);
   block(ls);  /* 'then' part */
   if (ls->t.token == TK_ELSE ||
       ls->t.token == TK_ELSEIF)  /* followed by 'else'/'elseif'? */
     luaK_concat(fs, escapelist, luaK_jump(fs));  /* must jump over it */
   luaK_patchtohere(fs, condtrue);
 }
 
 
 static void ifstat (LexState *ls, int line) {
   /* ifstat -> IF cond THEN block {ELSEIF cond THEN block} [ELSE block] END */
   FuncState *fs = ls->fs;
   int escapelist = NO_JUMP;  /* exit list for finished parts */
   test_then_block(ls, &escapelist);  /* IF cond THEN block */
   while (ls->t.token == TK_ELSEIF)
     test_then_block(ls, &escapelist);  /* ELSEIF cond THEN block */
   if (testnext(ls, TK_ELSE))
     block(ls);  /* 'else' part */
   check_match(ls, TK_END, TK_IF, line);
   luaK_patchtohere(fs, escapelist);  /* patch escape list to 'if' end */
 }
 
 
 static void localfunc (LexState *ls) {
   expdesc b;
   FuncState *fs = ls->fs;
   int fvar = fs->nactvar;  /* function's variable index */
   new_localvar(ls, str_checkname(ls));  /* new local variable */
   adjustlocalvars(ls, 1);  /* enter its scope */
   body(ls, &b, 0, ls->linenumber);  /* function created in next register */
   /* debug information will only see the variable after this point! */
   localdebuginfo(fs, fvar)->startpc = fs->pc;
 }
 
 
 static lu_byte getlocalattribute (LexState *ls) {
   /* ATTRIB -> ['<' Name '>'] */
   if (testnext(ls, '<')) {
     TString *ts = str_checkname(ls);
     const char *attr = getstr(ts);
     checknext(ls, '>');
     if (strcmp(attr, "const") == 0)
       return RDKCONST;  /* read-only variable */
     else if (strcmp(attr, "close") == 0)
       return RDKTOCLOSE;  /* to-be-closed variable */
     else
       luaK_semerror(ls,
         luaO_pushfstring(ls->L, "unknown attribute '%s'", attr));
   }
   return VDKREG;  /* regular variable */
 }
 
 
 static void checktoclose (FuncState *fs, int level) {
   if (level != -1) {  /* is there a to-be-closed variable? */
     marktobeclosed(fs);
     luaK_codeABC(fs, OP_TBC, reglevel(fs, level), 0, 0);
   }
 }
 
 
 static void localstat (LexState *ls) {
   /* stat -> LOCAL NAME ATTRIB { ',' NAME ATTRIB } ['=' explist] */
   FuncState *fs = ls->fs;
   int toclose = -1;  /* index of to-be-closed variable (if any) */
   Vardesc *var;  /* last variable */
   int vidx;  /* index of last variable */
   int nvars = 0;
   int nexps;
   expdesc e;
   do {
     TString *vname = str_checkname(ls);
     lu_byte kind = getlocalattribute(ls);
     vidx = new_localvarkind(ls, vname, kind);
     if (kind == RDKTOCLOSE) {  /* to-be-closed? */
       if (toclose != -1)  /* one already present? */
         luaK_semerror(ls, "multiple to-be-closed variables in local list");
       toclose = fs->nactvar + nvars;
     }
     nvars++;
   } while (testnext(ls, ','));
   if (testnext(ls, '='))
     nexps = explist(ls, &e);
   else {
     e.k = VVOID;
     nexps = 0;
   }
   var = getlocalvardesc(fs, vidx);  /* get last variable */
   if (nvars == nexps &&  /* no adjustments? */
       var->vd.kind == RDKCONST &&  /* last variable is const? */
       luaK_exp2const(fs, &e, &var->k)) {  /* compile-time constant? */
     var->vd.kind = RDKCTC;  /* variable is a compile-time constant */
     adjustlocalvars(ls, nvars - 1);  /* exclude last variable */
     fs->nactvar++;  /* but count it */
   }
   else {
     adjust_assign(ls, nvars, nexps, &e);
     adjustlocalvars(ls, nvars);
   }
   checktoclose(fs, toclose);
 }
 
 
 static int funcname (LexState *ls, expdesc *v) {
   /* funcname -> NAME {fieldsel} [':' NAME] */
   int ismethod = 0;
   singlevar(ls, v);
   while (ls->t.token == '.')
     fieldsel(ls, v);
   if (ls->t.token == ':') {
     ismethod = 1;
     fieldsel(ls, v);
   }
   return ismethod;
 }
 
 
 static void funcstat (LexState *ls, int line) {
   /* funcstat -> FUNCTION funcname body */
   int ismethod;
   expdesc v, b;
   luaX_next(ls);  /* skip FUNCTION */
   ismethod = funcname(ls, &v);
   body(ls, &b, ismethod, line);
   check_readonly(ls, &v);
   luaK_storevar(ls->fs, &v, &b);
   luaK_fixline(ls->fs, line);  /* definition "happens" in the first line */
 }
 
 
 static void exprstat (LexState *ls) {
   /* stat -> func | assignment */
   FuncState *fs = ls->fs;
   struct LHS_assign v;
   suffixedexp(ls, &v.v);
   if (ls->t.token == '=' || ls->t.token == ',') { /* stat -> assignment ? */
     v.prev = NULL;
     restassign(ls, &v, 1);
   }
   else {  /* stat -> func */
     Instruction *inst;
     check_condition(ls, v.v.k == VCALL, "syntax error");
     inst = &getinstruction(fs, &v.v);
     SETARG_C(*inst, 1);  /* call statement uses no results */
   }
 }
 
 
 static void retstat (LexState *ls) {
   /* stat -> RETURN [explist] [';'] */
   FuncState *fs = ls->fs;
   expdesc e;
   int nret;  /* number of values being returned */
   int first = luaY_nvarstack(fs);  /* first slot to be returned */
   if (block_follow(ls, 1) || ls->t.token == ';')
     nret = 0;  /* return no values */
   else {
     nret = explist(ls, &e);  /* optional return values */
     if (hasmultret(e.k)) {
       luaK_setmultret(fs, &e);
       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)) == luaY_nvarstack(fs));
       }
       nret = LUA_MULTRET;  /* return all values */
     }
     else {
       if (nret == 1)  /* only one single value? */
         first = luaK_exp2anyreg(fs, &e);  /* can use original slot */
       else {  /* values must go to the top of the stack */
         luaK_exp2nextreg(fs, &e);
         lua_assert(nret == fs->freereg - first);
       }
     }
   }
   luaK_ret(fs, first, nret);
   testnext(ls, ';');  /* skip optional semicolon */
 }
 
 
 static void statement (LexState *ls) {
   int line = ls->linenumber;  /* may be needed for error messages */
   enterlevel(ls);
   switch (ls->t.token) {
     case ';': {  /* stat -> ';' (empty statement) */
       luaX_next(ls);  /* skip ';' */
       break;
     }
     case TK_IF: {  /* stat -> ifstat */
       ifstat(ls, line);
       break;
     }
     case TK_WHILE: {  /* stat -> whilestat */
       whilestat(ls, line);
       break;
     }
     case TK_DO: {  /* stat -> DO block END */
       luaX_next(ls);  /* skip DO */
       block(ls);
       check_match(ls, TK_END, TK_DO, line);
       break;
     }
     case TK_FOR: {  /* stat -> forstat */
       forstat(ls, line);
       break;
     }
     case TK_REPEAT: {  /* stat -> repeatstat */
       repeatstat(ls, line);
       break;
     }
     case TK_FUNCTION: {  /* stat -> funcstat */
       funcstat(ls, line);
       break;
     }
     case TK_LOCAL: {  /* stat -> localstat */
       luaX_next(ls);  /* skip LOCAL */
       if (testnext(ls, TK_FUNCTION))  /* local function? */
         localfunc(ls);
       else
         localstat(ls);
       break;
     }
     case TK_DBCOLON: {  /* stat -> label */
       luaX_next(ls);  /* skip double colon */
       labelstat(ls, str_checkname(ls), line);
       break;
     }
     case TK_RETURN: {  /* stat -> retstat */
       luaX_next(ls);  /* skip RETURN */
       retstat(ls);
       break;
     }
     case TK_BREAK: {  /* stat -> breakstat */
       breakstat(ls, line);
       break;
     }
     case TK_GOTO: {  /* stat -> 'goto' NAME */
       luaX_next(ls);  /* skip 'goto' */
       gotostat(ls, line);
       break;
     }
     default: {  /* stat -> func | assignment */
       exprstat(ls);
       break;
     }
   }
   lua_assert(ls->fs->f->maxstacksize >= ls->fs->freereg &&
              ls->fs->freereg >= luaY_nvarstack(ls->fs));
   ls->fs->freereg = luaY_nvarstack(ls->fs);  /* free registers */
   leavelevel(ls);
 }
 
 /* }====================================================================== */
 
 /* }====================================================================== */
 
 
 /*
 ** compiles the main function, which is a regular vararg function with an
 ** upvalue named LUA_ENV
 */
 static void mainfunc (LexState *ls, FuncState *fs) {
   BlockCnt bl;
   Upvaldesc *env;
   open_func(ls, fs, &bl);
   setvararg(fs, 0);  /* main function is always declared vararg */
   env = allocupvalue(fs);  /* ...set environment upvalue */
   env->instack = 1;
   env->idx = 0;
   env->kind = VDKREG;
   env->name = ls->envn;
   luaC_objbarrier(ls->L, fs->f, env->name);
   luaX_next(ls);  /* read first token */
   statlist(ls);  /* parse main body */
   check(ls, TK_EOS);
   close_func(ls);
 }
 
 
 LClosure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
                        Dyndata *dyd, const char *name, int firstchar) {
   LexState lexstate;
   FuncState funcstate;
   LClosure *cl = luaF_newLclosure(L, 1);  /* create main closure */
   setclLvalue2s(L, L->top.p, cl);  /* anchor it (to avoid being collected) */
   luaD_inctop(L);
   lexstate.h = luaH_new(L);  /* create table for scanner */
   sethvalue2s(L, L->top.p, lexstate.h);  /* anchor it */
   luaD_inctop(L);
   funcstate.f = cl->p = luaF_newproto(L);
   luaC_objbarrier(L, cl, cl->p);
   funcstate.f->source = luaS_new(L, name);  /* create and anchor TString */
   luaC_objbarrier(L, funcstate.f, funcstate.f->source);
   lexstate.buff = buff;
   lexstate.dyd = dyd;
   dyd->actvar.n = dyd->gt.n = dyd->label.n = 0;
   luaX_setinput(L, &lexstate, z, funcstate.f->source, firstchar);
   mainfunc(&lexstate, &funcstate);
   lua_assert(!funcstate.prev && funcstate.nups == 1 && !lexstate.fs);
   /* all scopes should be correctly finished */
   lua_assert(dyd->actvar.n == 0 && dyd->gt.n == 0 && dyd->label.n == 0);
   L->top.p--;  /* remove scanner's table */
   return cl;  /* closure is on the stack, too */
 }