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  1. /*
  2. ** $Id: lparser.c,v 2.130.1.1 2013/04/12 18:48:47 roberto Exp $
  3. ** Lua Parser
  4. ** See Copyright Notice in lua.h
  5. */
  6.  
  7.  
  8. #include <string.h>
  9.  
  10. #define lparser_c
  11. #define LUA_CORE
  12.  
  13. #include "lua.h"
  14.  
  15. #include "lcode.h"
  16. #include "ldebug.h"
  17. #include "ldo.h"
  18. #include "lfunc.h"
  19. #include "llex.h"
  20. #include "lmem.h"
  21. #include "lobject.h"
  22. #include "lopcodes.h"
  23. #include "lparser.h"
  24. #include "lstate.h"
  25. #include "lstring.h"
  26. #include "ltable.h"
  27.  
  28.  
  29.  
  30. /* maximum number of local variables per function (must be smaller
  31.    than 250, due to the bytecode format) */
  32. #define MAXVARS         200
  33.  
  34.  
  35. #define hasmultret(k)           ((k) == VCALL || (k) == VVARARG)
  36.  
  37.  
  38.  
  39. /*
  40. ** nodes for block list (list of active blocks)
  41. */
  42. typedef struct BlockCnt {
  43.   struct BlockCnt *previous;  /* chain */
  44.   short firstlabel;  /* index of first label in this block */
  45.   short firstgoto;  /* index of first pending goto in this block */
  46.   lu_byte nactvar;  /* # active locals outside the block */
  47.   lu_byte upval;  /* true if some variable in the block is an upvalue */
  48.   lu_byte isloop;  /* true if `block' is a loop */
  49. } BlockCnt;
  50.  
  51.  
  52.  
  53. /*
  54. ** prototypes for recursive non-terminal functions
  55. */
  56. static void statement (LexState *ls);
  57. static void expr (LexState *ls, expdesc *v);
  58.  
  59.  
  60. static void anchor_token (LexState *ls) {
  61.   /* last token from outer function must be EOS */
  62.   lua_assert(ls->fs != NULL || ls->t.token == TK_EOS);
  63.   if (ls->t.token == TK_NAME || ls->t.token == TK_STRING) {
  64.     TString *ts = ls->t.seminfo.ts;
  65.     luaX_newstring(ls, getstr(ts), ts->tsv.len);
  66.   }
  67. }
  68.  
  69.  
  70. /* semantic error */
  71. static l_noret semerror (LexState *ls, const char *msg) {
  72.   ls->t.token = 0;  /* remove 'near to' from final message */
  73.   luaX_syntaxerror(ls, msg);
  74. }
  75.  
  76.  
  77. static l_noret error_expected (LexState *ls, int token) {
  78.   luaX_syntaxerror(ls,
  79.       luaO_pushfstring(ls->L, "%s expected", luaX_token2str(ls, token)));
  80. }
  81.  
  82.  
  83. static l_noret errorlimit (FuncState *fs, int limit, const char *what) {
  84.   lua_State *L = fs->ls->L;
  85.   const char *msg;
  86.   int line = fs->f->linedefined;
  87.   const char *where = (line == 0)
  88.                       ? "main function"
  89.                       : luaO_pushfstring(L, "function at line %d", line);
  90.   msg = luaO_pushfstring(L, "too many %s (limit is %d) in %s",
  91.                              what, limit, where);
  92.   luaX_syntaxerror(fs->ls, msg);
  93. }
  94.  
  95.  
  96. static void checklimit (FuncState *fs, int v, int l, const char *what) {
  97.   if (v > l) errorlimit(fs, l, what);
  98. }
  99.  
  100.  
  101. static int testnext (LexState *ls, int c) {
  102.   if (ls->t.token == c) {
  103.     luaX_next(ls);
  104.     return 1;
  105.   }
  106.   else return 0;
  107. }
  108.  
  109.  
  110. static void check (LexState *ls, int c) {
  111.   if (ls->t.token != c)
  112.     error_expected(ls, c);
  113. }
  114.  
  115.  
  116. static void checknext (LexState *ls, int c) {
  117.   check(ls, c);
  118.   luaX_next(ls);
  119. }
  120.  
  121.  
  122. #define check_condition(ls,c,msg)       { if (!(c)) luaX_syntaxerror(ls, msg); }
  123.  
  124.  
  125.  
  126. static void check_match (LexState *ls, int what, int who, int where) {
  127.   if (!testnext(ls, what)) {
  128.     if (where == ls->linenumber)
  129.       error_expected(ls, what);
  130.     else {
  131.       luaX_syntaxerror(ls, luaO_pushfstring(ls->L,
  132.              "%s expected (to close %s at line %d)",
  133.               luaX_token2str(ls, what), luaX_token2str(ls, who), where));
  134.     }
  135.   }
  136. }
  137.  
  138.  
  139. static TString *str_checkname (LexState *ls) {
  140.   TString *ts;
  141.   check(ls, TK_NAME);
  142.   ts = ls->t.seminfo.ts;
  143.   luaX_next(ls);
  144.   return ts;
  145. }
  146.  
  147.  
  148. static void init_exp (expdesc *e, expkind k, int i) {
  149.   e->f = e->t = NO_JUMP;
  150.   e->k = k;
  151.   e->u.info = i;
  152. }
  153.  
  154.  
  155. static void codestring (LexState *ls, expdesc *e, TString *s) {
  156.   init_exp(e, VK, luaK_stringK(ls->fs, s));
  157. }
  158.  
  159.  
  160. static void checkname (LexState *ls, expdesc *e) {
  161.   codestring(ls, e, str_checkname(ls));
  162. }
  163.  
  164.  
  165. static int registerlocalvar (LexState *ls, TString *varname) {
  166.   FuncState *fs = ls->fs;
  167.   Proto *f = fs->f;
  168.   int oldsize = f->sizelocvars;
  169.   luaM_growvector(ls->L, f->locvars, fs->nlocvars, f->sizelocvars,
  170.                   LocVar, SHRT_MAX, "local variables");
  171.   while (oldsize < f->sizelocvars) f->locvars[oldsize++].varname = NULL;
  172.   f->locvars[fs->nlocvars].varname = varname;
  173.   luaC_objbarrier(ls->L, f, varname);
  174.   return fs->nlocvars++;
  175. }
  176.  
  177.  
  178. static void new_localvar (LexState *ls, TString *name) {
  179.   FuncState *fs = ls->fs;
  180.   Dyndata *dyd = ls->dyd;
  181.   int reg = registerlocalvar(ls, name);
  182.   checklimit(fs, dyd->actvar.n + 1 - fs->firstlocal,
  183.                   MAXVARS, "local variables");
  184.   luaM_growvector(ls->L, dyd->actvar.arr, dyd->actvar.n + 1,
  185.                   dyd->actvar.size, Vardesc, MAX_INT, "local variables");
  186.   dyd->actvar.arr[dyd->actvar.n++].idx = cast(short, reg);
  187. }
  188.  
  189.  
  190. static void new_localvarliteral_ (LexState *ls, const char *name, size_t sz) {
  191.   new_localvar(ls, luaX_newstring(ls, name, sz));
  192. }
  193.  
  194. #define new_localvarliteral(ls,v) \
  195.         new_localvarliteral_(ls, "" v, (sizeof(v)/sizeof(char))-1)
  196.  
  197.  
  198. static LocVar *getlocvar (FuncState *fs, int i) {
  199.   int idx = fs->ls->dyd->actvar.arr[fs->firstlocal + i].idx;
  200.   lua_assert(idx < fs->nlocvars);
  201.   return &fs->f->locvars[idx];
  202. }
  203.  
  204.  
  205. static void adjustlocalvars (LexState *ls, int nvars) {
  206.   FuncState *fs = ls->fs;
  207.   fs->nactvar = cast_byte(fs->nactvar + nvars);
  208.   for (; nvars; nvars--) {
  209.     getlocvar(fs, fs->nactvar - nvars)->startpc = fs->pc;
  210.   }
  211. }
  212.  
  213.  
  214. static void removevars (FuncState *fs, int tolevel) {
  215.   fs->ls->dyd->actvar.n -= (fs->nactvar - tolevel);
  216.   while (fs->nactvar > tolevel)
  217.     getlocvar(fs, --fs->nactvar)->endpc = fs->pc;
  218. }
  219.  
  220.  
  221. static int searchupvalue (FuncState *fs, TString *name) {
  222.   int i;
  223.   Upvaldesc *up = fs->f->upvalues;
  224.   for (i = 0; i < fs->nups; i++) {
  225.     if (luaS_eqstr(up[i].name, name)) return i;
  226.   }
  227.   return -1;  /* not found */
  228. }
  229.  
  230.  
  231. static int newupvalue (FuncState *fs, TString *name, expdesc *v) {
  232.   Proto *f = fs->f;
  233.   int oldsize = f->sizeupvalues;
  234.   checklimit(fs, fs->nups + 1, MAXUPVAL, "upvalues");
  235.   luaM_growvector(fs->ls->L, f->upvalues, fs->nups, f->sizeupvalues,
  236.                   Upvaldesc, MAXUPVAL, "upvalues");
  237.   while (oldsize < f->sizeupvalues) f->upvalues[oldsize++].name = NULL;
  238.   f->upvalues[fs->nups].instack = (v->k == VLOCAL);
  239.   f->upvalues[fs->nups].idx = cast_byte(v->u.info);
  240.   f->upvalues[fs->nups].name = name;
  241.   luaC_objbarrier(fs->ls->L, f, name);
  242.   return fs->nups++;
  243. }
  244.  
  245.  
  246. static int searchvar (FuncState *fs, TString *n) {
  247.   int i;
  248.   for (i = cast_int(fs->nactvar) - 1; i >= 0; i--) {
  249.     if (luaS_eqstr(n, getlocvar(fs, i)->varname))
  250.       return i;
  251.   }
  252.   return -1;  /* not found */
  253. }
  254.  
  255.  
  256. /*
  257.   Mark block where variable at given level was defined
  258.   (to emit close instructions later).
  259. */
  260. static void markupval (FuncState *fs, int level) {
  261.   BlockCnt *bl = fs->bl;
  262.   while (bl->nactvar > level) bl = bl->previous;
  263.   bl->upval = 1;
  264. }
  265.  
  266.  
  267. /*
  268.   Find variable with given name 'n'. If it is an upvalue, add this
  269.   upvalue into all intermediate functions.
  270. */
  271. static int singlevaraux (FuncState *fs, TString *n, expdesc *var, int base) {
  272.   if (fs == NULL)  /* no more levels? */
  273.     return VVOID;  /* default is global */
  274.   else {
  275.     int v = searchvar(fs, n);  /* look up locals at current level */
  276.     if (v >= 0) {  /* found? */
  277.       init_exp(var, VLOCAL, v);  /* variable is local */
  278.       if (!base)
  279.         markupval(fs, v);  /* local will be used as an upval */
  280.       return VLOCAL;
  281.     }
  282.     else {  /* not found as local at current level; try upvalues */
  283.       int idx = searchupvalue(fs, n);  /* try existing upvalues */
  284.       if (idx < 0) {  /* not found? */
  285.         if (singlevaraux(fs->prev, n, var, 0) == VVOID) /* try upper levels */
  286.           return VVOID;  /* not found; is a global */
  287.         /* else was LOCAL or UPVAL */
  288.         idx  = newupvalue(fs, n, var);  /* will be a new upvalue */
  289.       }
  290.       init_exp(var, VUPVAL, idx);
  291.       return VUPVAL;
  292.     }
  293.   }
  294. }
  295.  
  296.  
  297. static void singlevar (LexState *ls, expdesc *var) {
  298.   TString *varname = str_checkname(ls);
  299.   FuncState *fs = ls->fs;
  300.   if (singlevaraux(fs, varname, var, 1) == VVOID) {  /* global name? */
  301.     expdesc key;
  302.     singlevaraux(fs, ls->envn, var, 1);  /* get environment variable */
  303.     lua_assert(var->k == VLOCAL || var->k == VUPVAL);
  304.     codestring(ls, &key, varname);  /* key is variable name */
  305.     luaK_indexed(fs, var, &key);  /* env[varname] */
  306.   }
  307. }
  308.  
  309.  
  310. static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e) {
  311.   FuncState *fs = ls->fs;
  312.   int extra = nvars - nexps;
  313.   if (hasmultret(e->k)) {
  314.     extra++;  /* includes call itself */
  315.     if (extra < 0) extra = 0;
  316.     luaK_setreturns(fs, e, extra);  /* last exp. provides the difference */
  317.     if (extra > 1) luaK_reserveregs(fs, extra-1);
  318.   }
  319.   else {
  320.     if (e->k != VVOID) luaK_exp2nextreg(fs, e);  /* close last expression */
  321.     if (extra > 0) {
  322.       int reg = fs->freereg;
  323.       luaK_reserveregs(fs, extra);
  324.       luaK_nil(fs, reg, extra);
  325.     }
  326.   }
  327. }
  328.  
  329.  
  330. static void enterlevel (LexState *ls) {
  331.   lua_State *L = ls->L;
  332.   ++L->nCcalls;
  333.   checklimit(ls->fs, L->nCcalls, LUAI_MAXCCALLS, "C levels");
  334. }
  335.  
  336.  
  337. #define leavelevel(ls)  ((ls)->L->nCcalls--)
  338.  
  339.  
  340. static void closegoto (LexState *ls, int g, Labeldesc *label) {
  341.   int i;
  342.   FuncState *fs = ls->fs;
  343.   Labellist *gl = &ls->dyd->gt;
  344.   Labeldesc *gt = &gl->arr[g];
  345.   lua_assert(luaS_eqstr(gt->name, label->name));
  346.   if (gt->nactvar < label->nactvar) {
  347.     TString *vname = getlocvar(fs, gt->nactvar)->varname;
  348.     const char *msg = luaO_pushfstring(ls->L,
  349.       "<goto %s> at line %d jumps into the scope of local " LUA_QS,
  350.       getstr(gt->name), gt->line, getstr(vname));
  351.     semerror(ls, msg);
  352.   }
  353.   luaK_patchlist(fs, gt->pc, label->pc);
  354.   /* remove goto from pending list */
  355.   for (i = g; i < gl->n - 1; i++)
  356.     gl->arr[i] = gl->arr[i + 1];
  357.   gl->n--;
  358. }
  359.  
  360.  
  361. /*
  362. ** try to close a goto with existing labels; this solves backward jumps
  363. */
  364. static int findlabel (LexState *ls, int g) {
  365.   int i;
  366.   BlockCnt *bl = ls->fs->bl;
  367.   Dyndata *dyd = ls->dyd;
  368.   Labeldesc *gt = &dyd->gt.arr[g];
  369.   /* check labels in current block for a match */
  370.   for (i = bl->firstlabel; i < dyd->label.n; i++) {
  371.     Labeldesc *lb = &dyd->label.arr[i];
  372.     if (luaS_eqstr(lb->name, gt->name)) {  /* correct label? */
  373.       if (gt->nactvar > lb->nactvar &&
  374.           (bl->upval || dyd->label.n > bl->firstlabel))
  375.         luaK_patchclose(ls->fs, gt->pc, lb->nactvar);
  376.       closegoto(ls, g, lb);  /* close it */
  377.       return 1;
  378.     }
  379.   }
  380.   return 0;  /* label not found; cannot close goto */
  381. }
  382.  
  383.  
  384. static int newlabelentry (LexState *ls, Labellist *l, TString *name,
  385.                           int line, int pc) {
  386.   int n = l->n;
  387.   luaM_growvector(ls->L, l->arr, n, l->size,
  388.                   Labeldesc, SHRT_MAX, "labels/gotos");
  389.   l->arr[n].name = name;
  390.   l->arr[n].line = line;
  391.   l->arr[n].nactvar = ls->fs->nactvar;
  392.   l->arr[n].pc = pc;
  393.   l->n++;
  394.   return n;
  395. }
  396.  
  397.  
  398. /*
  399. ** check whether new label 'lb' matches any pending gotos in current
  400. ** block; solves forward jumps
  401. */
  402. static void findgotos (LexState *ls, Labeldesc *lb) {
  403.   Labellist *gl = &ls->dyd->gt;
  404.   int i = ls->fs->bl->firstgoto;
  405.   while (i < gl->n) {
  406.     if (luaS_eqstr(gl->arr[i].name, lb->name))
  407.       closegoto(ls, i, lb);
  408.     else
  409.       i++;
  410.   }
  411. }
  412.  
  413.  
  414. /*
  415. ** "export" pending gotos to outer level, to check them against
  416. ** outer labels; if the block being exited has upvalues, and
  417. ** the goto exits the scope of any variable (which can be the
  418. ** upvalue), close those variables being exited.
  419. */
  420. static void movegotosout (FuncState *fs, BlockCnt *bl) {
  421.   int i = bl->firstgoto;
  422.   Labellist *gl = &fs->ls->dyd->gt;
  423.   /* correct pending gotos to current block and try to close it
  424.      with visible labels */
  425.   while (i < gl->n) {
  426.     Labeldesc *gt = &gl->arr[i];
  427.     if (gt->nactvar > bl->nactvar) {
  428.       if (bl->upval)
  429.         luaK_patchclose(fs, gt->pc, bl->nactvar);
  430.       gt->nactvar = bl->nactvar;
  431.     }
  432.     if (!findlabel(fs->ls, i))
  433.       i++;  /* move to next one */
  434.   }
  435. }
  436.  
  437.  
  438. static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isloop) {
  439.   bl->isloop = isloop;
  440.   bl->nactvar = fs->nactvar;
  441.   bl->firstlabel = fs->ls->dyd->label.n;
  442.   bl->firstgoto = fs->ls->dyd->gt.n;
  443.   bl->upval = 0;
  444.   bl->previous = fs->bl;
  445.   fs->bl = bl;
  446.   lua_assert(fs->freereg == fs->nactvar);
  447. }
  448.  
  449.  
  450. /*
  451. ** create a label named "break" to resolve break statements
  452. */
  453. static void breaklabel (LexState *ls) {
  454.   TString *n = luaS_new(ls->L, "break");
  455.   int l = newlabelentry(ls, &ls->dyd->label, n, 0, ls->fs->pc);
  456.   findgotos(ls, &ls->dyd->label.arr[l]);
  457. }
  458.  
  459. /*
  460. ** generates an error for an undefined 'goto'; choose appropriate
  461. ** message when label name is a reserved word (which can only be 'break')
  462. */
  463. static l_noret undefgoto (LexState *ls, Labeldesc *gt) {
  464.   const char *msg = isreserved(gt->name)
  465.                     ? "<%s> at line %d not inside a loop"
  466.                     : "no visible label " LUA_QS " for <goto> at line %d";
  467.   msg = luaO_pushfstring(ls->L, msg, getstr(gt->name), gt->line);
  468.   semerror(ls, msg);
  469. }
  470.  
  471.  
  472. static void leaveblock (FuncState *fs) {
  473.   BlockCnt *bl = fs->bl;
  474.   LexState *ls = fs->ls;
  475.   if (bl->previous && bl->upval) {
  476.     /* create a 'jump to here' to close upvalues */
  477.     int j = luaK_jump(fs);
  478.     luaK_patchclose(fs, j, bl->nactvar);
  479.     luaK_patchtohere(fs, j);
  480.   }
  481.   if (bl->isloop)
  482.     breaklabel(ls);  /* close pending breaks */
  483.   fs->bl = bl->previous;
  484.   removevars(fs, bl->nactvar);
  485.   lua_assert(bl->nactvar == fs->nactvar);
  486.   fs->freereg = fs->nactvar;  /* free registers */
  487.   ls->dyd->label.n = bl->firstlabel;  /* remove local labels */
  488.   if (bl->previous)  /* inner block? */
  489.     movegotosout(fs, bl);  /* update pending gotos to outer block */
  490.   else if (bl->firstgoto < ls->dyd->gt.n)  /* pending gotos in outer block? */
  491.     undefgoto(ls, &ls->dyd->gt.arr[bl->firstgoto]);  /* error */
  492. }
  493.  
  494.  
  495. /*
  496. ** adds a new prototype into list of prototypes
  497. */
  498. static Proto *addprototype (LexState *ls) {
  499.   Proto *clp;
  500.   lua_State *L = ls->L;
  501.   FuncState *fs = ls->fs;
  502.   Proto *f = fs->f;  /* prototype of current function */
  503.   if (fs->np >= f->sizep) {
  504.     int oldsize = f->sizep;
  505.     luaM_growvector(L, f->p, fs->np, f->sizep, Proto *, MAXARG_Bx, "functions");
  506.     while (oldsize < f->sizep) f->p[oldsize++] = NULL;
  507.   }
  508.   f->p[fs->np++] = clp = luaF_newproto(L);
  509.   luaC_objbarrier(L, f, clp);
  510.   return clp;
  511. }
  512.  
  513.  
  514. /*
  515. ** codes instruction to create new closure in parent function.
  516. ** The OP_CLOSURE instruction must use the last available register,
  517. ** so that, if it invokes the GC, the GC knows which registers
  518. ** are in use at that time.
  519. */
  520. static void codeclosure (LexState *ls, expdesc *v) {
  521.   FuncState *fs = ls->fs->prev;
  522.   init_exp(v, VRELOCABLE, luaK_codeABx(fs, OP_CLOSURE, 0, fs->np - 1));
  523.   luaK_exp2nextreg(fs, v);  /* fix it at the last register */
  524. }
  525.  
  526.  
  527. static void open_func (LexState *ls, FuncState *fs, BlockCnt *bl) {
  528.   lua_State *L = ls->L;
  529.   Proto *f;
  530.   fs->prev = ls->fs;  /* linked list of funcstates */
  531.   fs->ls = ls;
  532.   ls->fs = fs;
  533.   fs->pc = 0;
  534.   fs->lasttarget = 0;
  535.   fs->jpc = NO_JUMP;
  536.   fs->freereg = 0;
  537.   fs->nk = 0;
  538.   fs->np = 0;
  539.   fs->nups = 0;
  540.   fs->nlocvars = 0;
  541.   fs->nactvar = 0;
  542.   fs->firstlocal = ls->dyd->actvar.n;
  543.   fs->bl = NULL;
  544.   f = fs->f;
  545.   f->source = ls->source;
  546.   f->maxstacksize = 2;  /* registers 0/1 are always valid */
  547.   fs->h = luaH_new(L);
  548.   /* anchor table of constants (to avoid being collected) */
  549.   sethvalue2s(L, L->top, fs->h);
  550.   incr_top(L);
  551.   enterblock(fs, bl, 0);
  552. }
  553.  
  554.  
  555. static void close_func (LexState *ls) {
  556.   lua_State *L = ls->L;
  557.   FuncState *fs = ls->fs;
  558.   Proto *f = fs->f;
  559.   luaK_ret(fs, 0, 0);  /* final return */
  560.   leaveblock(fs);
  561.   luaM_reallocvector(L, f->code, f->sizecode, fs->pc, Instruction);
  562.   f->sizecode = fs->pc;
  563.   luaM_reallocvector(L, f->lineinfo, f->sizelineinfo, fs->pc, int);
  564.   f->sizelineinfo = fs->pc;
  565.   luaM_reallocvector(L, f->k, f->sizek, fs->nk, TValue);
  566.   f->sizek = fs->nk;
  567.   luaM_reallocvector(L, f->p, f->sizep, fs->np, Proto *);
  568.   f->sizep = fs->np;
  569.   luaM_reallocvector(L, f->locvars, f->sizelocvars, fs->nlocvars, LocVar);
  570.   f->sizelocvars = fs->nlocvars;
  571.   luaM_reallocvector(L, f->upvalues, f->sizeupvalues, fs->nups, Upvaldesc);
  572.   f->sizeupvalues = fs->nups;
  573.   lua_assert(fs->bl == NULL);
  574.   ls->fs = fs->prev;
  575.   /* last token read was anchored in defunct function; must re-anchor it */
  576.   anchor_token(ls);
  577.   L->top--;  /* pop table of constants */
  578.   luaC_checkGC(L);
  579. }
  580.  
  581.  
  582.  
  583. /*============================================================*/
  584. /* GRAMMAR RULES */
  585. /*============================================================*/
  586.  
  587.  
  588. /*
  589. ** check whether current token is in the follow set of a block.
  590. ** 'until' closes syntactical blocks, but do not close scope,
  591. ** so it handled in separate.
  592. */
  593. static int block_follow (LexState *ls, int withuntil) {
  594.   switch (ls->t.token) {
  595.     case TK_ELSE: case TK_ELSEIF:
  596.     case TK_END: case TK_EOS:
  597.       return 1;
  598.     case TK_UNTIL: return withuntil;
  599.     default: return 0;
  600.   }
  601. }
  602.  
  603.  
  604. static void statlist (LexState *ls) {
  605.   /* statlist -> { stat [`;'] } */
  606.   while (!block_follow(ls, 1)) {
  607.     if (ls->t.token == TK_RETURN) {
  608.       statement(ls);
  609.       return;  /* 'return' must be last statement */
  610.     }
  611.     statement(ls);
  612.   }
  613. }
  614.  
  615.  
  616. static void fieldsel (LexState *ls, expdesc *v) {
  617.   /* fieldsel -> ['.' | ':'] NAME */
  618.   FuncState *fs = ls->fs;
  619.   expdesc key;
  620.   luaK_exp2anyregup(fs, v);
  621.   luaX_next(ls);  /* skip the dot or colon */
  622.   checkname(ls, &key);
  623.   luaK_indexed(fs, v, &key);
  624. }
  625.  
  626.  
  627. static void yindex (LexState *ls, expdesc *v) {
  628.   /* index -> '[' expr ']' */
  629.   luaX_next(ls);  /* skip the '[' */
  630.   expr(ls, v);
  631.   luaK_exp2val(ls->fs, v);
  632.   checknext(ls, ']');
  633. }
  634.  
  635.  
  636. /*
  637. ** {======================================================================
  638. ** Rules for Constructors
  639. ** =======================================================================
  640. */
  641.  
  642.  
  643. struct ConsControl {
  644.   expdesc v;  /* last list item read */
  645.   expdesc *t;  /* table descriptor */
  646.   int nh;  /* total number of `record' elements */
  647.   int na;  /* total number of array elements */
  648.   int tostore;  /* number of array elements pending to be stored */
  649. };
  650.  
  651.  
  652. static void recfield (LexState *ls, struct ConsControl *cc) {
  653.   /* recfield -> (NAME | `['exp1`]') = exp1 */
  654.   FuncState *fs = ls->fs;
  655.   int reg = ls->fs->freereg;
  656.   expdesc key, val;
  657.   int rkkey;
  658.   if (ls->t.token == TK_NAME) {
  659.     checklimit(fs, cc->nh, MAX_INT, "items in a constructor");
  660.     checkname(ls, &key);
  661.   }
  662.   else  /* ls->t.token == '[' */
  663.     yindex(ls, &key);
  664.   cc->nh++;
  665.   checknext(ls, '=');
  666.   rkkey = luaK_exp2RK(fs, &key);
  667.   expr(ls, &val);
  668.   luaK_codeABC(fs, OP_SETTABLE, cc->t->u.info, rkkey, luaK_exp2RK(fs, &val));
  669.   fs->freereg = reg;  /* free registers */
  670. }
  671.  
  672.  
  673. static void closelistfield (FuncState *fs, struct ConsControl *cc) {
  674.   if (cc->v.k == VVOID) return;  /* there is no list item */
  675.   luaK_exp2nextreg(fs, &cc->v);
  676.   cc->v.k = VVOID;
  677.   if (cc->tostore == LFIELDS_PER_FLUSH) {
  678.     luaK_setlist(fs, cc->t->u.info, cc->na, cc->tostore);  /* flush */
  679.     cc->tostore = 0;  /* no more items pending */
  680.   }
  681. }
  682.  
  683.  
  684. static void lastlistfield (FuncState *fs, struct ConsControl *cc) {
  685.   if (cc->tostore == 0) return;
  686.   if (hasmultret(cc->v.k)) {
  687.     luaK_setmultret(fs, &cc->v);
  688.     luaK_setlist(fs, cc->t->u.info, cc->na, LUA_MULTRET);
  689.     cc->na--;  /* do not count last expression (unknown number of elements) */
  690.   }
  691.   else {
  692.     if (cc->v.k != VVOID)
  693.       luaK_exp2nextreg(fs, &cc->v);
  694.     luaK_setlist(fs, cc->t->u.info, cc->na, cc->tostore);
  695.   }
  696. }
  697.  
  698.  
  699. static void listfield (LexState *ls, struct ConsControl *cc) {
  700.   /* listfield -> exp */
  701.   expr(ls, &cc->v);
  702.   checklimit(ls->fs, cc->na, MAX_INT, "items in a constructor");
  703.   cc->na++;
  704.   cc->tostore++;
  705. }
  706.  
  707.  
  708. static void field (LexState *ls, struct ConsControl *cc) {
  709.   /* field -> listfield | recfield */
  710.   switch(ls->t.token) {
  711.     case TK_NAME: {  /* may be 'listfield' or 'recfield' */
  712.       if (luaX_lookahead(ls) != '=')  /* expression? */
  713.         listfield(ls, cc);
  714.       else
  715.         recfield(ls, cc);
  716.       break;
  717.     }
  718.     case '[': {
  719.       recfield(ls, cc);
  720.       break;
  721.     }
  722.     default: {
  723.       listfield(ls, cc);
  724.       break;
  725.     }
  726.   }
  727. }
  728.  
  729.  
  730. static void constructor (LexState *ls, expdesc *t) {
  731.   /* constructor -> '{' [ field { sep field } [sep] ] '}'
  732.      sep -> ',' | ';' */
  733.   FuncState *fs = ls->fs;
  734.   int line = ls->linenumber;
  735.   int pc = luaK_codeABC(fs, OP_NEWTABLE, 0, 0, 0);
  736.   struct ConsControl cc;
  737.   cc.na = cc.nh = cc.tostore = 0;
  738.   cc.t = t;
  739.   init_exp(t, VRELOCABLE, pc);
  740.   init_exp(&cc.v, VVOID, 0);  /* no value (yet) */
  741.   luaK_exp2nextreg(ls->fs, t);  /* fix it at stack top */
  742.   checknext(ls, '{');
  743.   do {
  744.     lua_assert(cc.v.k == VVOID || cc.tostore > 0);
  745.     if (ls->t.token == '}') break;
  746.     closelistfield(fs, &cc);
  747.     field(ls, &cc);
  748.   } while (testnext(ls, ',') || testnext(ls, ';'));
  749.   check_match(ls, '}', '{', line);
  750.   lastlistfield(fs, &cc);
  751.   SETARG_B(fs->f->code[pc], luaO_int2fb(cc.na)); /* set initial array size */
  752.   SETARG_C(fs->f->code[pc], luaO_int2fb(cc.nh));  /* set initial table size */
  753. }
  754.  
  755. /* }====================================================================== */
  756.  
  757.  
  758.  
  759. static void parlist (LexState *ls) {
  760.   /* parlist -> [ param { `,' param } ] */
  761.   FuncState *fs = ls->fs;
  762.   Proto *f = fs->f;
  763.   int nparams = 0;
  764.   f->is_vararg = 0;
  765.   if (ls->t.token != ')') {  /* is `parlist' not empty? */
  766.     do {
  767.       switch (ls->t.token) {
  768.         case TK_NAME: {  /* param -> NAME */
  769.           new_localvar(ls, str_checkname(ls));
  770.           nparams++;
  771.           break;
  772.         }
  773.         case TK_DOTS: {  /* param -> `...' */
  774.           luaX_next(ls);
  775.           f->is_vararg = 1;
  776.           break;
  777.         }
  778.         default: luaX_syntaxerror(ls, "<name> or " LUA_QL("...") " expected");
  779.       }
  780.     } while (!f->is_vararg && testnext(ls, ','));
  781.   }
  782.   adjustlocalvars(ls, nparams);
  783.   f->numparams = cast_byte(fs->nactvar);
  784.   luaK_reserveregs(fs, fs->nactvar);  /* reserve register for parameters */
  785. }
  786.  
  787.  
  788. static void body (LexState *ls, expdesc *e, int ismethod, int line) {
  789.   /* body ->  `(' parlist `)' block END */
  790.   FuncState new_fs;
  791.   BlockCnt bl;
  792.   new_fs.f = addprototype(ls);
  793.   new_fs.f->linedefined = line;
  794.   open_func(ls, &new_fs, &bl);
  795.   checknext(ls, '(');
  796.   if (ismethod) {
  797.     new_localvarliteral(ls, "self");  /* create 'self' parameter */
  798.     adjustlocalvars(ls, 1);
  799.   }
  800.   parlist(ls);
  801.   checknext(ls, ')');
  802.   statlist(ls);
  803.   new_fs.f->lastlinedefined = ls->linenumber;
  804.   check_match(ls, TK_END, TK_FUNCTION, line);
  805.   codeclosure(ls, e);
  806.   close_func(ls);
  807. }
  808.  
  809.  
  810. static int explist (LexState *ls, expdesc *v) {
  811.   /* explist -> expr { `,' expr } */
  812.   int n = 1;  /* at least one expression */
  813.   expr(ls, v);
  814.   while (testnext(ls, ',')) {
  815.     luaK_exp2nextreg(ls->fs, v);
  816.     expr(ls, v);
  817.     n++;
  818.   }
  819.   return n;
  820. }
  821.  
  822.  
  823. static void funcargs (LexState *ls, expdesc *f, int line) {
  824.   FuncState *fs = ls->fs;
  825.   expdesc args;
  826.   int base, nparams;
  827.   switch (ls->t.token) {
  828.     case '(': {  /* funcargs -> `(' [ explist ] `)' */
  829.       luaX_next(ls);
  830.       if (ls->t.token == ')')  /* arg list is empty? */
  831.         args.k = VVOID;
  832.       else {
  833.         explist(ls, &args);
  834.         luaK_setmultret(fs, &args);
  835.       }
  836.       check_match(ls, ')', '(', line);
  837.       break;
  838.     }
  839.     case '{': {  /* funcargs -> constructor */
  840.       constructor(ls, &args);
  841.       break;
  842.     }
  843.     case TK_STRING: {  /* funcargs -> STRING */
  844.       codestring(ls, &args, ls->t.seminfo.ts);
  845.       luaX_next(ls);  /* must use `seminfo' before `next' */
  846.       break;
  847.     }
  848.     default: {
  849.       luaX_syntaxerror(ls, "function arguments expected");
  850.     }
  851.   }
  852.   lua_assert(f->k == VNONRELOC);
  853.   base = f->u.info;  /* base register for call */
  854.   if (hasmultret(args.k))
  855.     nparams = LUA_MULTRET;  /* open call */
  856.   else {
  857.     if (args.k != VVOID)
  858.       luaK_exp2nextreg(fs, &args);  /* close last argument */
  859.     nparams = fs->freereg - (base+1);
  860.   }
  861.   init_exp(f, VCALL, luaK_codeABC(fs, OP_CALL, base, nparams+1, 2));
  862.   luaK_fixline(fs, line);
  863.   fs->freereg = base+1;  /* call remove function and arguments and leaves
  864.                             (unless changed) one result */
  865. }
  866.  
  867.  
  868.  
  869.  
  870. /*
  871. ** {======================================================================
  872. ** Expression parsing
  873. ** =======================================================================
  874. */
  875.  
  876.  
  877. static void primaryexp (LexState *ls, expdesc *v) {
  878.   /* primaryexp -> NAME | '(' expr ')' */
  879.   switch (ls->t.token) {
  880.     case '(': {
  881.       int line = ls->linenumber;
  882.       luaX_next(ls);
  883.       expr(ls, v);
  884.       check_match(ls, ')', '(', line);
  885.       luaK_dischargevars(ls->fs, v);
  886.       return;
  887.     }
  888.     case TK_NAME: {
  889.       singlevar(ls, v);
  890.       return;
  891.     }
  892.     default: {
  893.       luaX_syntaxerror(ls, "unexpected symbol");
  894.     }
  895.   }
  896. }
  897.  
  898.  
  899. static void suffixedexp (LexState *ls, expdesc *v) {
  900.   /* suffixedexp ->
  901.        primaryexp { '.' NAME | '[' exp ']' | ':' NAME funcargs | funcargs } */
  902.   FuncState *fs = ls->fs;
  903.   int line = ls->linenumber;
  904.   primaryexp(ls, v);
  905.   for (;;) {
  906.     switch (ls->t.token) {
  907.       case '.': {  /* fieldsel */
  908.         fieldsel(ls, v);
  909.         break;
  910.       }
  911.       case '[': {  /* `[' exp1 `]' */
  912.         expdesc key;
  913.         luaK_exp2anyregup(fs, v);
  914.         yindex(ls, &key);
  915.         luaK_indexed(fs, v, &key);
  916.         break;
  917.       }
  918.       case ':': {  /* `:' NAME funcargs */
  919.         expdesc key;
  920.         luaX_next(ls);
  921.         checkname(ls, &key);
  922.         luaK_self(fs, v, &key);
  923.         funcargs(ls, v, line);
  924.         break;
  925.       }
  926.       case '(': case TK_STRING: case '{': {  /* funcargs */
  927.         luaK_exp2nextreg(fs, v);
  928.         funcargs(ls, v, line);
  929.         break;
  930.       }
  931.       default: return;
  932.     }
  933.   }
  934. }
  935.  
  936.  
  937. static void simpleexp (LexState *ls, expdesc *v) {
  938.   /* simpleexp -> NUMBER | STRING | NIL | TRUE | FALSE | ... |
  939.                   constructor | FUNCTION body | suffixedexp */
  940.   switch (ls->t.token) {
  941.     case TK_NUMBER: {
  942.       init_exp(v, VKNUM, 0);
  943.       v->u.nval = ls->t.seminfo.r;
  944.       break;
  945.     }
  946.     case TK_STRING: {
  947.       codestring(ls, v, ls->t.seminfo.ts);
  948.       break;
  949.     }
  950.     case TK_NIL: {
  951.       init_exp(v, VNIL, 0);
  952.       break;
  953.     }
  954.     case TK_TRUE: {
  955.       init_exp(v, VTRUE, 0);
  956.       break;
  957.     }
  958.     case TK_FALSE: {
  959.       init_exp(v, VFALSE, 0);
  960.       break;
  961.     }
  962.     case TK_DOTS: {  /* vararg */
  963.       FuncState *fs = ls->fs;
  964.       check_condition(ls, fs->f->is_vararg,
  965.                       "cannot use " LUA_QL("...") " outside a vararg function");
  966.       init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 1, 0));
  967.       break;
  968.     }
  969.     case '{': {  /* constructor */
  970.       constructor(ls, v);
  971.       return;
  972.     }
  973.     case TK_FUNCTION: {
  974.       luaX_next(ls);
  975.       body(ls, v, 0, ls->linenumber);
  976.       return;
  977.     }
  978.     default: {
  979.       suffixedexp(ls, v);
  980.       return;
  981.     }
  982.   }
  983.   luaX_next(ls);
  984. }
  985.  
  986.  
  987. static UnOpr getunopr (int op) {
  988.   switch (op) {
  989.     case TK_NOT: return OPR_NOT;
  990.     case '-': return OPR_MINUS;
  991.     case '#': return OPR_LEN;
  992.     default: return OPR_NOUNOPR;
  993.   }
  994. }
  995.  
  996.  
  997. static BinOpr getbinopr (int op) {
  998.   switch (op) {
  999.     case '+': return OPR_ADD;
  1000.     case '-': return OPR_SUB;
  1001.     case '*': return OPR_MUL;
  1002.     case '/': return OPR_DIV;
  1003.     case '%': return OPR_MOD;
  1004.     case '^': return OPR_POW;
  1005.     case TK_CONCAT: return OPR_CONCAT;
  1006.     case TK_NE: return OPR_NE;
  1007.     case TK_EQ: return OPR_EQ;
  1008.     case '<': return OPR_LT;
  1009.     case TK_LE: return OPR_LE;
  1010.     case '>': return OPR_GT;
  1011.     case TK_GE: return OPR_GE;
  1012.     case TK_AND: return OPR_AND;
  1013.     case TK_OR: return OPR_OR;
  1014.     default: return OPR_NOBINOPR;
  1015.   }
  1016. }
  1017.  
  1018.  
  1019. static const struct {
  1020.   lu_byte left;  /* left priority for each binary operator */
  1021.   lu_byte right; /* right priority */
  1022. } priority[] = {  /* ORDER OPR */
  1023.    {6, 6}, {6, 6}, {7, 7}, {7, 7}, {7, 7},  /* `+' `-' `*' `/' `%' */
  1024.    {10, 9}, {5, 4},                 /* ^, .. (right associative) */
  1025.    {3, 3}, {3, 3}, {3, 3},          /* ==, <, <= */
  1026.    {3, 3}, {3, 3}, {3, 3},          /* ~=, >, >= */
  1027.    {2, 2}, {1, 1}                   /* and, or */
  1028. };
  1029.  
  1030. #define UNARY_PRIORITY  8  /* priority for unary operators */
  1031.  
  1032.  
  1033. /*
  1034. ** subexpr -> (simpleexp | unop subexpr) { binop subexpr }
  1035. ** where `binop' is any binary operator with a priority higher than `limit'
  1036. */
  1037. static BinOpr subexpr (LexState *ls, expdesc *v, int limit) {
  1038.   BinOpr op;
  1039.   UnOpr uop;
  1040.   enterlevel(ls);
  1041.   uop = getunopr(ls->t.token);
  1042.   if (uop != OPR_NOUNOPR) {
  1043.     int line = ls->linenumber;
  1044.     luaX_next(ls);
  1045.     subexpr(ls, v, UNARY_PRIORITY);
  1046.     luaK_prefix(ls->fs, uop, v, line);
  1047.   }
  1048.   else simpleexp(ls, v);
  1049.   /* expand while operators have priorities higher than `limit' */
  1050.   op = getbinopr(ls->t.token);
  1051.   while (op != OPR_NOBINOPR && priority[op].left > limit) {
  1052.     expdesc v2;
  1053.     BinOpr nextop;
  1054.     int line = ls->linenumber;
  1055.     luaX_next(ls);
  1056.     luaK_infix(ls->fs, op, v);
  1057.     /* read sub-expression with higher priority */
  1058.     nextop = subexpr(ls, &v2, priority[op].right);
  1059.     luaK_posfix(ls->fs, op, v, &v2, line);
  1060.     op = nextop;
  1061.   }
  1062.   leavelevel(ls);
  1063.   return op;  /* return first untreated operator */
  1064. }
  1065.  
  1066.  
  1067. static void expr (LexState *ls, expdesc *v) {
  1068.   subexpr(ls, v, 0);
  1069. }
  1070.  
  1071. /* }==================================================================== */
  1072.  
  1073.  
  1074.  
  1075. /*
  1076. ** {======================================================================
  1077. ** Rules for Statements
  1078. ** =======================================================================
  1079. */
  1080.  
  1081.  
  1082. static void block (LexState *ls) {
  1083.   /* block -> statlist */
  1084.   FuncState *fs = ls->fs;
  1085.   BlockCnt bl;
  1086.   enterblock(fs, &bl, 0);
  1087.   statlist(ls);
  1088.   leaveblock(fs);
  1089. }
  1090.  
  1091.  
  1092. /*
  1093. ** structure to chain all variables in the left-hand side of an
  1094. ** assignment
  1095. */
  1096. struct LHS_assign {
  1097.   struct LHS_assign *prev;
  1098.   expdesc v;  /* variable (global, local, upvalue, or indexed) */
  1099. };
  1100.  
  1101.  
  1102. /*
  1103. ** check whether, in an assignment to an upvalue/local variable, the
  1104. ** upvalue/local variable is begin used in a previous assignment to a
  1105. ** table. If so, save original upvalue/local value in a safe place and
  1106. ** use this safe copy in the previous assignment.
  1107. */
  1108. static void check_conflict (LexState *ls, struct LHS_assign *lh, expdesc *v) {
  1109.   FuncState *fs = ls->fs;
  1110.   int extra = fs->freereg;  /* eventual position to save local variable */
  1111.   int conflict = 0;
  1112.   for (; lh; lh = lh->prev) {  /* check all previous assignments */
  1113.     if (lh->v.k == VINDEXED) {  /* assigning to a table? */
  1114.       /* table is the upvalue/local being assigned now? */
  1115.       if (lh->v.u.ind.vt == v->k && lh->v.u.ind.t == v->u.info) {
  1116.         conflict = 1;
  1117.         lh->v.u.ind.vt = VLOCAL;
  1118.         lh->v.u.ind.t = extra;  /* previous assignment will use safe copy */
  1119.       }
  1120.       /* index is the local being assigned? (index cannot be upvalue) */
  1121.       if (v->k == VLOCAL && lh->v.u.ind.idx == v->u.info) {
  1122.         conflict = 1;
  1123.         lh->v.u.ind.idx = extra;  /* previous assignment will use safe copy */
  1124.       }
  1125.     }
  1126.   }
  1127.   if (conflict) {
  1128.     /* copy upvalue/local value to a temporary (in position 'extra') */
  1129.     OpCode op = (v->k == VLOCAL) ? OP_MOVE : OP_GETUPVAL;
  1130.     luaK_codeABC(fs, op, extra, v->u.info, 0);
  1131.     luaK_reserveregs(fs, 1);
  1132.   }
  1133. }
  1134.  
  1135.  
  1136. static void assignment (LexState *ls, struct LHS_assign *lh, int nvars) {
  1137.   expdesc e;
  1138.   check_condition(ls, vkisvar(lh->v.k), "syntax error");
  1139.   if (testnext(ls, ',')) {  /* assignment -> ',' suffixedexp assignment */
  1140.     struct LHS_assign nv;
  1141.     nv.prev = lh;
  1142.     suffixedexp(ls, &nv.v);
  1143.     if (nv.v.k != VINDEXED)
  1144.       check_conflict(ls, lh, &nv.v);
  1145.     checklimit(ls->fs, nvars + ls->L->nCcalls, LUAI_MAXCCALLS,
  1146.                     "C levels");
  1147.     assignment(ls, &nv, nvars+1);
  1148.   }
  1149.   else {  /* assignment -> `=' explist */
  1150.     int nexps;
  1151.     checknext(ls, '=');
  1152.     nexps = explist(ls, &e);
  1153.     if (nexps != nvars) {
  1154.       adjust_assign(ls, nvars, nexps, &e);
  1155.       if (nexps > nvars)
  1156.         ls->fs->freereg -= nexps - nvars;  /* remove extra values */
  1157.     }
  1158.     else {
  1159.       luaK_setoneret(ls->fs, &e);  /* close last expression */
  1160.       luaK_storevar(ls->fs, &lh->v, &e);
  1161.       return;  /* avoid default */
  1162.     }
  1163.   }
  1164.   init_exp(&e, VNONRELOC, ls->fs->freereg-1);  /* default assignment */
  1165.   luaK_storevar(ls->fs, &lh->v, &e);
  1166. }
  1167.  
  1168.  
  1169. static int cond (LexState *ls) {
  1170.   /* cond -> exp */
  1171.   expdesc v;
  1172.   expr(ls, &v);  /* read condition */
  1173.   if (v.k == VNIL) v.k = VFALSE;  /* `falses' are all equal here */
  1174.   luaK_goiftrue(ls->fs, &v);
  1175.   return v.f;
  1176. }
  1177.  
  1178.  
  1179. static void gotostat (LexState *ls, int pc) {
  1180.   int line = ls->linenumber;
  1181.   TString *label;
  1182.   int g;
  1183.   if (testnext(ls, TK_GOTO))
  1184.     label = str_checkname(ls);
  1185.   else {
  1186.     luaX_next(ls);  /* skip break */
  1187.     label = luaS_new(ls->L, "break");
  1188.   }
  1189.   g = newlabelentry(ls, &ls->dyd->gt, label, line, pc);
  1190.   findlabel(ls, g);  /* close it if label already defined */
  1191. }
  1192.  
  1193.  
  1194. /* check for repeated labels on the same block */
  1195. static void checkrepeated (FuncState *fs, Labellist *ll, TString *label) {
  1196.   int i;
  1197.   for (i = fs->bl->firstlabel; i < ll->n; i++) {
  1198.     if (luaS_eqstr(label, ll->arr[i].name)) {
  1199.       const char *msg = luaO_pushfstring(fs->ls->L,
  1200.                           "label " LUA_QS " already defined on line %d",
  1201.                           getstr(label), ll->arr[i].line);
  1202.       semerror(fs->ls, msg);
  1203.     }
  1204.   }
  1205. }
  1206.  
  1207.  
  1208. /* skip no-op statements */
  1209. static void skipnoopstat (LexState *ls) {
  1210.   while (ls->t.token == ';' || ls->t.token == TK_DBCOLON)
  1211.     statement(ls);
  1212. }
  1213.  
  1214.  
  1215. static void labelstat (LexState *ls, TString *label, int line) {
  1216.   /* label -> '::' NAME '::' */
  1217.   FuncState *fs = ls->fs;
  1218.   Labellist *ll = &ls->dyd->label;
  1219.   int l;  /* index of new label being created */
  1220.   checkrepeated(fs, ll, label);  /* check for repeated labels */
  1221.   checknext(ls, TK_DBCOLON);  /* skip double colon */
  1222.   /* create new entry for this label */
  1223.   l = newlabelentry(ls, ll, label, line, fs->pc);
  1224.   skipnoopstat(ls);  /* skip other no-op statements */
  1225.   if (block_follow(ls, 0)) {  /* label is last no-op statement in the block? */
  1226.     /* assume that locals are already out of scope */
  1227.     ll->arr[l].nactvar = fs->bl->nactvar;
  1228.   }
  1229.   findgotos(ls, &ll->arr[l]);
  1230. }
  1231.  
  1232.  
  1233. static void whilestat (LexState *ls, int line) {
  1234.   /* whilestat -> WHILE cond DO block END */
  1235.   FuncState *fs = ls->fs;
  1236.   int whileinit;
  1237.   int condexit;
  1238.   BlockCnt bl;
  1239.   luaX_next(ls);  /* skip WHILE */
  1240.   whileinit = luaK_getlabel(fs);
  1241.   condexit = cond(ls);
  1242.   enterblock(fs, &bl, 1);
  1243.   checknext(ls, TK_DO);
  1244.   block(ls);
  1245.   luaK_jumpto(fs, whileinit);
  1246.   check_match(ls, TK_END, TK_WHILE, line);
  1247.   leaveblock(fs);
  1248.   luaK_patchtohere(fs, condexit);  /* false conditions finish the loop */
  1249. }
  1250.  
  1251.  
  1252. static void repeatstat (LexState *ls, int line) {
  1253.   /* repeatstat -> REPEAT block UNTIL cond */
  1254.   int condexit;
  1255.   FuncState *fs = ls->fs;
  1256.   int repeat_init = luaK_getlabel(fs);
  1257.   BlockCnt bl1, bl2;
  1258.   enterblock(fs, &bl1, 1);  /* loop block */
  1259.   enterblock(fs, &bl2, 0);  /* scope block */
  1260.   luaX_next(ls);  /* skip REPEAT */
  1261.   statlist(ls);
  1262.   check_match(ls, TK_UNTIL, TK_REPEAT, line);
  1263.   condexit = cond(ls);  /* read condition (inside scope block) */
  1264.   if (bl2.upval)  /* upvalues? */
  1265.     luaK_patchclose(fs, condexit, bl2.nactvar);
  1266.   leaveblock(fs);  /* finish scope */
  1267.   luaK_patchlist(fs, condexit, repeat_init);  /* close the loop */
  1268.   leaveblock(fs);  /* finish loop */
  1269. }
  1270.  
  1271.  
  1272. static int exp1 (LexState *ls) {
  1273.   expdesc e;
  1274.   int reg;
  1275.   expr(ls, &e);
  1276.   luaK_exp2nextreg(ls->fs, &e);
  1277.   lua_assert(e.k == VNONRELOC);
  1278.   reg = e.u.info;
  1279.   return reg;
  1280. }
  1281.  
  1282.  
  1283. static void forbody (LexState *ls, int base, int line, int nvars, int isnum) {
  1284.   /* forbody -> DO block */
  1285.   BlockCnt bl;
  1286.   FuncState *fs = ls->fs;
  1287.   int prep, endfor;
  1288.   adjustlocalvars(ls, 3);  /* control variables */
  1289.   checknext(ls, TK_DO);
  1290.   prep = isnum ? luaK_codeAsBx(fs, OP_FORPREP, base, NO_JUMP) : luaK_jump(fs);
  1291.   enterblock(fs, &bl, 0);  /* scope for declared variables */
  1292.   adjustlocalvars(ls, nvars);
  1293.   luaK_reserveregs(fs, nvars);
  1294.   block(ls);
  1295.   leaveblock(fs);  /* end of scope for declared variables */
  1296.   luaK_patchtohere(fs, prep);
  1297.   if (isnum)  /* numeric for? */
  1298.     endfor = luaK_codeAsBx(fs, OP_FORLOOP, base, NO_JUMP);
  1299.   else {  /* generic for */
  1300.     luaK_codeABC(fs, OP_TFORCALL, base, 0, nvars);
  1301.     luaK_fixline(fs, line);
  1302.     endfor = luaK_codeAsBx(fs, OP_TFORLOOP, base + 2, NO_JUMP);
  1303.   }
  1304.   luaK_patchlist(fs, endfor, prep + 1);
  1305.   luaK_fixline(fs, line);
  1306. }
  1307.  
  1308.  
  1309. static void fornum (LexState *ls, TString *varname, int line) {
  1310.   /* fornum -> NAME = exp1,exp1[,exp1] forbody */
  1311.   FuncState *fs = ls->fs;
  1312.   int base = fs->freereg;
  1313.   new_localvarliteral(ls, "(for index)");
  1314.   new_localvarliteral(ls, "(for limit)");
  1315.   new_localvarliteral(ls, "(for step)");
  1316.   new_localvar(ls, varname);
  1317.   checknext(ls, '=');
  1318.   exp1(ls);  /* initial value */
  1319.   checknext(ls, ',');
  1320.   exp1(ls);  /* limit */
  1321.   if (testnext(ls, ','))
  1322.     exp1(ls);  /* optional step */
  1323.   else {  /* default step = 1 */
  1324.     luaK_codek(fs, fs->freereg, luaK_numberK(fs, 1));
  1325.     luaK_reserveregs(fs, 1);
  1326.   }
  1327.   forbody(ls, base, line, 1, 1);
  1328. }
  1329.  
  1330.  
  1331. static void forlist (LexState *ls, TString *indexname) {
  1332.   /* forlist -> NAME {,NAME} IN explist forbody */
  1333.   FuncState *fs = ls->fs;
  1334.   expdesc e;
  1335.   int nvars = 4;  /* gen, state, control, plus at least one declared var */
  1336.   int line;
  1337.   int base = fs->freereg;
  1338.   /* create control variables */
  1339.   new_localvarliteral(ls, "(for generator)");
  1340.   new_localvarliteral(ls, "(for state)");
  1341.   new_localvarliteral(ls, "(for control)");
  1342.   /* create declared variables */
  1343.   new_localvar(ls, indexname);
  1344.   while (testnext(ls, ',')) {
  1345.     new_localvar(ls, str_checkname(ls));
  1346.     nvars++;
  1347.   }
  1348.   checknext(ls, TK_IN);
  1349.   line = ls->linenumber;
  1350.   adjust_assign(ls, 3, explist(ls, &e), &e);
  1351.   luaK_checkstack(fs, 3);  /* extra space to call generator */
  1352.   forbody(ls, base, line, nvars - 3, 0);
  1353. }
  1354.  
  1355.  
  1356. static void forstat (LexState *ls, int line) {
  1357.   /* forstat -> FOR (fornum | forlist) END */
  1358.   FuncState *fs = ls->fs;
  1359.   TString *varname;
  1360.   BlockCnt bl;
  1361.   enterblock(fs, &bl, 1);  /* scope for loop and control variables */
  1362.   luaX_next(ls);  /* skip `for' */
  1363.   varname = str_checkname(ls);  /* first variable name */
  1364.   switch (ls->t.token) {
  1365.     case '=': fornum(ls, varname, line); break;
  1366.     case ',': case TK_IN: forlist(ls, varname); break;
  1367.     default: luaX_syntaxerror(ls, LUA_QL("=") " or " LUA_QL("in") " expected");
  1368.   }
  1369.   check_match(ls, TK_END, TK_FOR, line);
  1370.   leaveblock(fs);  /* loop scope (`break' jumps to this point) */
  1371. }
  1372.  
  1373.  
  1374. static void test_then_block (LexState *ls, int *escapelist) {
  1375.   /* test_then_block -> [IF | ELSEIF] cond THEN block */
  1376.   BlockCnt bl;
  1377.   FuncState *fs = ls->fs;
  1378.   expdesc v;
  1379.   int jf;  /* instruction to skip 'then' code (if condition is false) */
  1380.   luaX_next(ls);  /* skip IF or ELSEIF */
  1381.   expr(ls, &v);  /* read condition */
  1382.   checknext(ls, TK_THEN);
  1383.   if (ls->t.token == TK_GOTO || ls->t.token == TK_BREAK) {
  1384.     luaK_goiffalse(ls->fs, &v);  /* will jump to label if condition is true */
  1385.     enterblock(fs, &bl, 0);  /* must enter block before 'goto' */
  1386.     gotostat(ls, v.t);  /* handle goto/break */
  1387.     skipnoopstat(ls);  /* skip other no-op statements */
  1388.     if (block_follow(ls, 0)) {  /* 'goto' is the entire block? */
  1389.       leaveblock(fs);
  1390.       return;  /* and that is it */
  1391.     }
  1392.     else  /* must skip over 'then' part if condition is false */
  1393.       jf = luaK_jump(fs);
  1394.   }
  1395.   else {  /* regular case (not goto/break) */
  1396.     luaK_goiftrue(ls->fs, &v);  /* skip over block if condition is false */
  1397.     enterblock(fs, &bl, 0);
  1398.     jf = v.f;
  1399.   }
  1400.   statlist(ls);  /* `then' part */
  1401.   leaveblock(fs);
  1402.   if (ls->t.token == TK_ELSE ||
  1403.       ls->t.token == TK_ELSEIF)  /* followed by 'else'/'elseif'? */
  1404.     luaK_concat(fs, escapelist, luaK_jump(fs));  /* must jump over it */
  1405.   luaK_patchtohere(fs, jf);
  1406. }
  1407.  
  1408.  
  1409. static void ifstat (LexState *ls, int line) {
  1410.   /* ifstat -> IF cond THEN block {ELSEIF cond THEN block} [ELSE block] END */
  1411.   FuncState *fs = ls->fs;
  1412.   int escapelist = NO_JUMP;  /* exit list for finished parts */
  1413.   test_then_block(ls, &escapelist);  /* IF cond THEN block */
  1414.   while (ls->t.token == TK_ELSEIF)
  1415.     test_then_block(ls, &escapelist);  /* ELSEIF cond THEN block */
  1416.   if (testnext(ls, TK_ELSE))
  1417.     block(ls);  /* `else' part */
  1418.   check_match(ls, TK_END, TK_IF, line);
  1419.   luaK_patchtohere(fs, escapelist);  /* patch escape list to 'if' end */
  1420. }
  1421.  
  1422.  
  1423. static void localfunc (LexState *ls) {
  1424.   expdesc b;
  1425.   FuncState *fs = ls->fs;
  1426.   new_localvar(ls, str_checkname(ls));  /* new local variable */
  1427.   adjustlocalvars(ls, 1);  /* enter its scope */
  1428.   body(ls, &b, 0, ls->linenumber);  /* function created in next register */
  1429.   /* debug information will only see the variable after this point! */
  1430.   getlocvar(fs, b.u.info)->startpc = fs->pc;
  1431. }
  1432.  
  1433.  
  1434. static void localstat (LexState *ls) {
  1435.   /* stat -> LOCAL NAME {`,' NAME} [`=' explist] */
  1436.   int nvars = 0;
  1437.   int nexps;
  1438.   expdesc e;
  1439.   do {
  1440.     new_localvar(ls, str_checkname(ls));
  1441.     nvars++;
  1442.   } while (testnext(ls, ','));
  1443.   if (testnext(ls, '='))
  1444.     nexps = explist(ls, &e);
  1445.   else {
  1446.     e.k = VVOID;
  1447.     nexps = 0;
  1448.   }
  1449.   adjust_assign(ls, nvars, nexps, &e);
  1450.   adjustlocalvars(ls, nvars);
  1451. }
  1452.  
  1453.  
  1454. static int funcname (LexState *ls, expdesc *v) {
  1455.   /* funcname -> NAME {fieldsel} [`:' NAME] */
  1456.   int ismethod = 0;
  1457.   singlevar(ls, v);
  1458.   while (ls->t.token == '.')
  1459.     fieldsel(ls, v);
  1460.   if (ls->t.token == ':') {
  1461.     ismethod = 1;
  1462.     fieldsel(ls, v);
  1463.   }
  1464.   return ismethod;
  1465. }
  1466.  
  1467.  
  1468. static void funcstat (LexState *ls, int line) {
  1469.   /* funcstat -> FUNCTION funcname body */
  1470.   int ismethod;
  1471.   expdesc v, b;
  1472.   luaX_next(ls);  /* skip FUNCTION */
  1473.   ismethod = funcname(ls, &v);
  1474.   body(ls, &b, ismethod, line);
  1475.   luaK_storevar(ls->fs, &v, &b);
  1476.   luaK_fixline(ls->fs, line);  /* definition `happens' in the first line */
  1477. }
  1478.  
  1479.  
  1480. static void exprstat (LexState *ls) {
  1481.   /* stat -> func | assignment */
  1482.   FuncState *fs = ls->fs;
  1483.   struct LHS_assign v;
  1484.   suffixedexp(ls, &v.v);
  1485.   if (ls->t.token == '=' || ls->t.token == ',') { /* stat -> assignment ? */
  1486.     v.prev = NULL;
  1487.     assignment(ls, &v, 1);
  1488.   }
  1489.   else {  /* stat -> func */
  1490.     check_condition(ls, v.v.k == VCALL, "syntax error");
  1491.     SETARG_C(getcode(fs, &v.v), 1);  /* call statement uses no results */
  1492.   }
  1493. }
  1494.  
  1495.  
  1496. static void retstat (LexState *ls) {
  1497.   /* stat -> RETURN [explist] [';'] */
  1498.   FuncState *fs = ls->fs;
  1499.   expdesc e;
  1500.   int first, nret;  /* registers with returned values */
  1501.   if (block_follow(ls, 1) || ls->t.token == ';')
  1502.     first = nret = 0;  /* return no values */
  1503.   else {
  1504.     nret = explist(ls, &e);  /* optional return values */
  1505.     if (hasmultret(e.k)) {
  1506.       luaK_setmultret(fs, &e);
  1507.       if (e.k == VCALL && nret == 1) {  /* tail call? */
  1508.         SET_OPCODE(getcode(fs,&e), OP_TAILCALL);
  1509.         lua_assert(GETARG_A(getcode(fs,&e)) == fs->nactvar);
  1510.       }
  1511.       first = fs->nactvar;
  1512.       nret = LUA_MULTRET;  /* return all values */
  1513.     }
  1514.     else {
  1515.       if (nret == 1)  /* only one single value? */
  1516.         first = luaK_exp2anyreg(fs, &e);
  1517.       else {
  1518.         luaK_exp2nextreg(fs, &e);  /* values must go to the `stack' */
  1519.         first = fs->nactvar;  /* return all `active' values */
  1520.         lua_assert(nret == fs->freereg - first);
  1521.       }
  1522.     }
  1523.   }
  1524.   luaK_ret(fs, first, nret);
  1525.   testnext(ls, ';');  /* skip optional semicolon */
  1526. }
  1527.  
  1528.  
  1529. static void statement (LexState *ls) {
  1530.   int line = ls->linenumber;  /* may be needed for error messages */
  1531.   enterlevel(ls);
  1532.   switch (ls->t.token) {
  1533.     case ';': {  /* stat -> ';' (empty statement) */
  1534.       luaX_next(ls);  /* skip ';' */
  1535.       break;
  1536.     }
  1537.     case TK_IF: {  /* stat -> ifstat */
  1538.       ifstat(ls, line);
  1539.       break;
  1540.     }
  1541.     case TK_WHILE: {  /* stat -> whilestat */
  1542.       whilestat(ls, line);
  1543.       break;
  1544.     }
  1545.     case TK_DO: {  /* stat -> DO block END */
  1546.       luaX_next(ls);  /* skip DO */
  1547.       block(ls);
  1548.       check_match(ls, TK_END, TK_DO, line);
  1549.       break;
  1550.     }
  1551.     case TK_FOR: {  /* stat -> forstat */
  1552.       forstat(ls, line);
  1553.       break;
  1554.     }
  1555.     case TK_REPEAT: {  /* stat -> repeatstat */
  1556.       repeatstat(ls, line);
  1557.       break;
  1558.     }
  1559.     case TK_FUNCTION: {  /* stat -> funcstat */
  1560.       funcstat(ls, line);
  1561.       break;
  1562.     }
  1563.     case TK_LOCAL: {  /* stat -> localstat */
  1564.       luaX_next(ls);  /* skip LOCAL */
  1565.       if (testnext(ls, TK_FUNCTION))  /* local function? */
  1566.         localfunc(ls);
  1567.       else
  1568.         localstat(ls);
  1569.       break;
  1570.     }
  1571.     case TK_DBCOLON: {  /* stat -> label */
  1572.       luaX_next(ls);  /* skip double colon */
  1573.       labelstat(ls, str_checkname(ls), line);
  1574.       break;
  1575.     }
  1576.     case TK_RETURN: {  /* stat -> retstat */
  1577.       luaX_next(ls);  /* skip RETURN */
  1578.       retstat(ls);
  1579.       break;
  1580.     }
  1581.     case TK_BREAK:   /* stat -> breakstat */
  1582.     case TK_GOTO: {  /* stat -> 'goto' NAME */
  1583.       gotostat(ls, luaK_jump(ls->fs));
  1584.       break;
  1585.     }
  1586.     default: {  /* stat -> func | assignment */
  1587.       exprstat(ls);
  1588.       break;
  1589.     }
  1590.   }
  1591.   lua_assert(ls->fs->f->maxstacksize >= ls->fs->freereg &&
  1592.              ls->fs->freereg >= ls->fs->nactvar);
  1593.   ls->fs->freereg = ls->fs->nactvar;  /* free registers */
  1594.   leavelevel(ls);
  1595. }
  1596.  
  1597. /* }====================================================================== */
  1598.  
  1599.  
  1600. /*
  1601. ** compiles the main function, which is a regular vararg function with an
  1602. ** upvalue named LUA_ENV
  1603. */
  1604. static void mainfunc (LexState *ls, FuncState *fs) {
  1605.   BlockCnt bl;
  1606.   expdesc v;
  1607.   open_func(ls, fs, &bl);
  1608.   fs->f->is_vararg = 1;  /* main function is always vararg */
  1609.   init_exp(&v, VLOCAL, 0);  /* create and... */
  1610.   newupvalue(fs, ls->envn, &v);  /* ...set environment upvalue */
  1611.   luaX_next(ls);  /* read first token */
  1612.   statlist(ls);  /* parse main body */
  1613.   check(ls, TK_EOS);
  1614.   close_func(ls);
  1615. }
  1616.  
  1617.  
  1618. Closure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
  1619.                       Dyndata *dyd, const char *name, int firstchar) {
  1620.   LexState lexstate;
  1621.   FuncState funcstate;
  1622.   Closure *cl = luaF_newLclosure(L, 1);  /* create main closure */
  1623.   /* anchor closure (to avoid being collected) */
  1624.   setclLvalue(L, L->top, cl);
  1625.   incr_top(L);
  1626.   funcstate.f = cl->l.p = luaF_newproto(L);
  1627.   funcstate.f->source = luaS_new(L, name);  /* create and anchor TString */
  1628.   lexstate.buff = buff;
  1629.   lexstate.dyd = dyd;
  1630.   dyd->actvar.n = dyd->gt.n = dyd->label.n = 0;
  1631.   luaX_setinput(L, &lexstate, z, funcstate.f->source, firstchar);
  1632.   mainfunc(&lexstate, &funcstate);
  1633.   lua_assert(!funcstate.prev && funcstate.nups == 1 && !lexstate.fs);
  1634.   /* all scopes should be correctly finished */
  1635.   lua_assert(dyd->actvar.n == 0 && dyd->gt.n == 0 && dyd->label.n == 0);
  1636.   return cl;  /* it's on the stack too */
  1637. }
  1638.  
  1639.