liblua/ldo.c

   1 /*
   2 ** $Id: ldo.c,v 2.108 2012/10/01 14:05:04 roberto Exp $
   3 ** Stack and Call structure of Lua
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7
   8 #include <setjmp.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11
  12 #define ldo_c
  13 #define LUA_CORE
  14
  15 #include "lua.h"
  16
  17 #include "lapi.h"
  18 #include "ldebug.h"
  19 #include "ldo.h"
  20 #include "lfunc.h"
  21 #include "lgc.h"
  22 #include "lmem.h"
  23 #include "lobject.h"
  24 #include "lopcodes.h"
  25 #include "lparser.h"
  26 #include "lstate.h"
  27 #include "lstring.h"
  28 #include "ltable.h"
  29 #include "ltm.h"
  30 #include "lundump.h"
  31 #include "lvm.h"
  32 #include "lzio.h"
  33
  34
  35
  36
  37 /*
  38 ** {======================================================
  39 ** Error-recovery functions
  40 ** =======================================================
  41 */
  42
  43 /*
  44 ** LUAI_THROW/LUAI_TRY define how Lua does exception handling. By
  45 ** default, Lua handles errors with exceptions when compiling as
  46 ** C++ code, with _longjmp/_setjmp when asked to use them, and with
  47 ** longjmp/setjmp otherwise.
  48 */
  49 #if !defined(LUAI_THROW)
  50
  51 #if defined(__cplusplus) && !defined(LUA_USE_LONGJMP)
  52 /* C++ exceptions */
  53 #define LUAI_THROW(L,c)         throw(c)
  54 #define LUAI_TRY(L,c,a) \
  55         try { a } catch(...) { if ((c)->status == 0) (c)->status = -1; }
  56 #define luai_jmpbuf             int  /* dummy variable */
  57
  58 #elif defined(LUA_USE_ULONGJMP)
  59 /* in Unix, try _longjmp/_setjmp (more efficient) */
  60 #define LUAI_THROW(L,c)         _longjmp((c)->b, 1)
  61 #define LUAI_TRY(L,c,a)         if (_setjmp((c)->b) == 0) { a }
  62 #define luai_jmpbuf             jmp_buf
  63
  64 #else
  65 /* default handling with long jumps */
  66 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
  67 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
  68 #define luai_jmpbuf             jmp_buf
  69
  70 #endif
  71
  72 #endif
  73
  74
  75
  76 /* chain list of long jump buffers */
  77 struct lua_longjmp {
  78   struct lua_longjmp *previous;
  79   luai_jmpbuf b;
  80   volatile int status;  /* error code */
  81 };
  82
  83
  84 static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
  85   switch (errcode) {
  86     case LUA_ERRMEM: {  /* memory error? */
  87       setsvalue2s(L, oldtop, G(L)->memerrmsg); /* reuse preregistered msg. */
  88       break;
  89     }
  90     case LUA_ERRERR: {
  91       setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
  92       break;
  93     }
  94     default: {
  95       setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
  96       break;
  97     }
  98   }
  99   L->top = oldtop + 1;
 100 }
 101
 102
 103 l_noret luaD_throw (lua_State *L, int errcode) {
 104   if (L->errorJmp) {  /* thread has an error handler? */
 105     L->errorJmp->status = errcode;  /* set status */
 106     LUAI_THROW(L, L->errorJmp);  /* jump to it */
 107   }
 108   else {  /* thread has no error handler */
 109     L->status = cast_byte(errcode);  /* mark it as dead */
 110     if (G(L)->mainthread->errorJmp) {  /* main thread has a handler? */
 111       setobjs2s(L, G(L)->mainthread->top++, L->top - 1);  /* copy error obj. */
 112       luaD_throw(G(L)->mainthread, errcode);  /* re-throw in main thread */
 113     }
 114     else {  /* no handler at all; abort */
 115       if (G(L)->panic) {  /* panic function? */
 116         lua_unlock(L);
 117         G(L)->panic(L);  /* call it (last chance to jump out) */
 118       }
 119       abort();
 120     }
 121   }
 122 }
 123
 124
 125 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 126   unsigned short oldnCcalls = L->nCcalls;
 127   struct lua_longjmp lj;
 128   lj.status = LUA_OK;
 129   lj.previous = L->errorJmp;  /* chain new error handler */
 130   L->errorJmp = &lj;
 131   LUAI_TRY(L, &lj,
 132     (*f)(L, ud);
 133   );
 134   L->errorJmp = lj.previous;  /* restore old error handler */
 135   L->nCcalls = oldnCcalls;
 136   return lj.status;
 137 }
 138
 139 /* }====================================================== */
 140
 141
 142 static void correctstack (lua_State *L, TValue *oldstack) {
 143   CallInfo *ci;
 144   GCObject *up;
 145   L->top = (L->top - oldstack) + L->stack;
 146   for (up = L->openupval; up != NULL; up = up->gch.next)
 147     gco2uv(up)->v = (gco2uv(up)->v - oldstack) + L->stack;
 148   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 149     ci->top = (ci->top - oldstack) + L->stack;
 150     ci->func = (ci->func - oldstack) + L->stack;
 151     if (isLua(ci))
 152       ci->u.l.base = (ci->u.l.base - oldstack) + L->stack;
 153   }
 154 }
 155
 156
 157 /* some space for error handling */
 158 #define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)
 159
 160
 161 void luaD_reallocstack (lua_State *L, int newsize) {
 162   TValue *oldstack = L->stack;
 163   int lim = L->stacksize;
 164   lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
 165   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
 166   luaM_reallocvector(L, L->stack, L->stacksize, newsize, TValue);
 167   for (; lim < newsize; lim++)
 168     setnilvalue(L->stack + lim); /* erase new segment */
 169   L->stacksize = newsize;
 170   L->stack_last = L->stack + newsize - EXTRA_STACK;
 171   correctstack(L, oldstack);
 172 }
 173
 174
 175 void luaD_growstack (lua_State *L, int n) {
 176   int size = L->stacksize;
 177   if (size > LUAI_MAXSTACK)  /* error after extra size? */
 178     luaD_throw(L, LUA_ERRERR);
 179   else {
 180     int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
 181     int newsize = 2 * size;
 182     if (newsize > LUAI_MAXSTACK) newsize = LUAI_MAXSTACK;
 183     if (newsize < needed) newsize = needed;
 184     if (newsize > LUAI_MAXSTACK) {  /* stack overflow? */
 185       luaD_reallocstack(L, ERRORSTACKSIZE);
 186       luaG_runerror(L, "stack overflow");
 187     }
 188     else
 189       luaD_reallocstack(L, newsize);
 190   }
 191 }
 192
 193
 194 static int stackinuse (lua_State *L) {
 195   CallInfo *ci;
 196   StkId lim = L->top;
 197   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 198     lua_assert(ci->top <= L->stack_last);
 199     if (lim < ci->top) lim = ci->top;
 200   }
 201   return cast_int(lim - L->stack) + 1;  /* part of stack in use */
 202 }
 203
 204
 205 void luaD_shrinkstack (lua_State *L) {
 206   int inuse = stackinuse(L);
 207   int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
 208   if (goodsize > LUAI_MAXSTACK) goodsize = LUAI_MAXSTACK;
 209   if (inuse > LUAI_MAXSTACK ||  /* handling stack overflow? */
 210       goodsize >= L->stacksize)  /* would grow instead of shrink? */
 211     condmovestack(L);  /* don't change stack (change only for debugging) */
 212   else
 213     luaD_reallocstack(L, goodsize);  /* shrink it */
 214 }
 215
 216
 217 void luaD_hook (lua_State *L, int event, int line) {
 218   lua_Hook hook = L->hook;
 219   if (hook && L->allowhook) {
 220     CallInfo *ci = L->ci;
 221     ptrdiff_t top = savestack(L, L->top);
 222     ptrdiff_t ci_top = savestack(L, ci->top);
 223     lua_Debug ar;
 224     ar.event = event;
 225     ar.currentline = line;
 226     ar.i_ci = ci;
 227     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 228     ci->top = L->top + LUA_MINSTACK;
 229     lua_assert(ci->top <= L->stack_last);
 230     L->allowhook = 0;  /* cannot call hooks inside a hook */
 231     ci->callstatus |= CIST_HOOKED;
 232     lua_unlock(L);
 233     (*hook)(L, &ar);
 234     lua_lock(L);
 235     lua_assert(!L->allowhook);
 236     L->allowhook = 1;
 237     ci->top = restorestack(L, ci_top);
 238     L->top = restorestack(L, top);
 239     ci->callstatus &= ~CIST_HOOKED;
 240   }
 241 }
 242
 243
 244 static void callhook (lua_State *L, CallInfo *ci) {
 245   int hook = LUA_HOOKCALL;
 246   ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */
 247   if (isLua(ci->previous) &&
 248       GET_OPCODE(*(ci->previous->u.l.savedpc - 1)) == OP_TAILCALL) {
 249     ci->callstatus |= CIST_TAIL;
 250     hook = LUA_HOOKTAILCALL;
 251   }
 252   luaD_hook(L, hook, -1);
 253   ci->u.l.savedpc--;  /* correct 'pc' */
 254 }
 255
 256
 257 static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
 258   int i;
 259   int nfixargs = p->numparams;
 260   StkId base, fixed;
 261   lua_assert(actual >= nfixargs);
 262   /* move fixed parameters to final position */
 263   fixed = L->top - actual;  /* first fixed argument */
 264   base = L->top;  /* final position of first argument */
 265   for (i=0; i<nfixargs; i++) {
 266     setobjs2s(L, L->top++, fixed + i);
 267     setnilvalue(fixed + i);
 268   }
 269   return base;
 270 }
 271
 272
 273 static StkId tryfuncTM (lua_State *L, StkId func) {
 274   const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
 275   StkId p;
 276   ptrdiff_t funcr = savestack(L, func);
 277   if (!ttisfunction(tm))
 278     luaG_typeerror(L, func, "call");
 279   /* Open a hole inside the stack at `func' */
 280   for (p = L->top; p > func; p--) setobjs2s(L, p, p-1);
 281   incr_top(L);
 282   func = restorestack(L, funcr);  /* previous call may change stack */
 283   setobj2s(L, func, tm);  /* tag method is the new function to be called */
 284   return func;
 285 }
 286
 287
 288
 289 #define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))
 290
 291
 292 /*
 293 ** returns true if function has been executed (C function)
 294 */
 295 int luaD_precall (lua_State *L, StkId func, int nresults) {
 296   lua_CFunction f;
 297   CallInfo *ci;
 298   int n;  /* number of arguments (Lua) or returns (C) */
 299   ptrdiff_t funcr = savestack(L, func);
 300   switch (ttype(func)) {
 301     case LUA_TLCF:  /* light C function */
 302       f = fvalue(func);
 303       goto Cfunc;
 304     case LUA_TCCL: {  /* C closure */
 305       f = clCvalue(func)->f;
 306      Cfunc:
 307       luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 308       ci = next_ci(L);  /* now 'enter' new function */
 309       ci->nresults = nresults;
 310       ci->func = restorestack(L, funcr);
 311       ci->top = L->top + LUA_MINSTACK;
 312       lua_assert(ci->top <= L->stack_last);
 313       ci->callstatus = 0;
 314       luaC_checkGC(L);  /* stack grow uses memory */
 315       if (L->hookmask & LUA_MASKCALL)
 316         luaD_hook(L, LUA_HOOKCALL, -1);
 317       lua_unlock(L);
 318       n = (*f)(L);  /* do the actual call */
 319       lua_lock(L);
 320       api_checknelems(L, n);
 321       luaD_poscall(L, L->top - n);
 322       return 1;
 323     }
 324     case LUA_TLCL: {  /* Lua function: prepare its call */
 325       StkId base;
 326       Proto *p = clLvalue(func)->p;
 327       luaD_checkstack(L, p->maxstacksize);
 328       func = restorestack(L, funcr);
 329       n = cast_int(L->top - func) - 1;  /* number of real arguments */
 330       for (; n < p->numparams; n++)
 331         setnilvalue(L->top++);  /* complete missing arguments */
 332       base = (!p->is_vararg) ? func + 1 : adjust_varargs(L, p, n);
 333       ci = next_ci(L);  /* now 'enter' new function */
 334       ci->nresults = nresults;
 335       ci->func = func;
 336       ci->u.l.base = base;
 337       ci->top = base + p->maxstacksize;
 338       lua_assert(ci->top <= L->stack_last);
 339       ci->u.l.savedpc = p->code;  /* starting point */
 340       ci->callstatus = CIST_LUA;
 341       L->top = ci->top;
 342       luaC_checkGC(L);  /* stack grow uses memory */
 343       if (L->hookmask & LUA_MASKCALL)
 344         callhook(L, ci);
 345       return 0;
 346     }
 347     default: {  /* not a function */
 348       func = tryfuncTM(L, func);  /* retry with 'function' tag method */
 349       return luaD_precall(L, func, nresults);  /* now it must be a function */
 350     }
 351   }
 352 }
 353
 354
 355 int luaD_poscall (lua_State *L, StkId firstResult) {
 356   StkId res;
 357   int wanted, i;
 358   CallInfo *ci = L->ci;
 359   if (L->hookmask & (LUA_MASKRET | LUA_MASKLINE)) {
 360     if (L->hookmask & LUA_MASKRET) {
 361       ptrdiff_t fr = savestack(L, firstResult);  /* hook may change stack */
 362       luaD_hook(L, LUA_HOOKRET, -1);
 363       firstResult = restorestack(L, fr);
 364     }
 365     L->oldpc = ci->previous->u.l.savedpc;  /* 'oldpc' for caller function */
 366   }
 367   res = ci->func;  /* res == final position of 1st result */
 368   wanted = ci->nresults;
 369   L->ci = ci = ci->previous;  /* back to caller */
 370   /* move results to correct place */
 371   for (i = wanted; i != 0 && firstResult < L->top; i--)
 372     setobjs2s(L, res++, firstResult++);
 373   while (i-- > 0)
 374     setnilvalue(res++);
 375   L->top = res;
 376   return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
 377 }
 378
 379
 380 /*
 381 ** Call a function (C or Lua). The function to be called is at *func.
 382 ** The arguments are on the stack, right after the function.
 383 ** When returns, all the results are on the stack, starting at the original
 384 ** function position.
 385 */
 386 void luaD_call (lua_State *L, StkId func, int nResults, int allowyield) {
 387   if (++L->nCcalls >= LUAI_MAXCCALLS) {
 388     if (L->nCcalls == LUAI_MAXCCALLS)
 389       luaG_runerror(L, "C stack overflow");
 390     else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
 391       luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
 392   }
 393   if (!allowyield) L->nny++;
 394   if (!luaD_precall(L, func, nResults))  /* is a Lua function? */
 395     luaV_execute(L);  /* call it */
 396   if (!allowyield) L->nny--;
 397   L->nCcalls--;
 398 }
 399
 400
 401 static void finishCcall (lua_State *L) {
 402   CallInfo *ci = L->ci;
 403   int n;
 404   lua_assert(ci->u.c.k != NULL);  /* must have a continuation */
 405   lua_assert(L->nny == 0);
 406   if (ci->callstatus & CIST_YPCALL) {  /* was inside a pcall? */
 407     ci->callstatus &= ~CIST_YPCALL;  /* finish 'lua_pcall' */
 408     L->errfunc = ci->u.c.old_errfunc;
 409   }
 410   /* finish 'lua_callk'/'lua_pcall' */
 411   adjustresults(L, ci->nresults);
 412   /* call continuation function */
 413   if (!(ci->callstatus & CIST_STAT))  /* no call status? */
 414     ci->u.c.status = LUA_YIELD;  /* 'default' status */
 415   lua_assert(ci->u.c.status != LUA_OK);
 416   ci->callstatus = (ci->callstatus & ~(CIST_YPCALL | CIST_STAT)) | CIST_YIELDED;
 417   lua_unlock(L);
 418   n = (*ci->u.c.k)(L);
 419   lua_lock(L);
 420   api_checknelems(L, n);
 421   /* finish 'luaD_precall' */
 422   luaD_poscall(L, L->top - n);
 423 }
 424
 425
 426 static void unroll (lua_State *L, void *ud) {
 427   UNUSED(ud);
 428   for (;;) {
 429     if (L->ci == &L->base_ci)  /* stack is empty? */
 430       return;  /* coroutine finished normally */
 431     if (!isLua(L->ci))  /* C function? */
 432       finishCcall(L);
 433     else {  /* Lua function */
 434       luaV_finishOp(L);  /* finish interrupted instruction */
 435       luaV_execute(L);  /* execute down to higher C 'boundary' */
 436     }
 437   }
 438 }
 439
 440
 441 /*
 442 ** check whether thread has a suspended protected call
 443 */
 444 static CallInfo *findpcall (lua_State *L) {
 445   CallInfo *ci;
 446   for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
 447     if (ci->callstatus & CIST_YPCALL)
 448       return ci;
 449   }
 450   return NULL;  /* no pending pcall */
 451 }
 452
 453
 454 static int recover (lua_State *L, int status) {
 455   StkId oldtop;
 456   CallInfo *ci = findpcall(L);
 457   if (ci == NULL) return 0;  /* no recovery point */
 458   /* "finish" luaD_pcall */
 459   oldtop = restorestack(L, ci->extra);
 460   luaF_close(L, oldtop);
 461   seterrorobj(L, status, oldtop);
 462   L->ci = ci;
 463   L->allowhook = ci->u.c.old_allowhook;
 464   L->nny = 0;  /* should be zero to be yieldable */
 465   luaD_shrinkstack(L);
 466   L->errfunc = ci->u.c.old_errfunc;
 467   ci->callstatus |= CIST_STAT;  /* call has error status */
 468   ci->u.c.status = status;  /* (here it is) */
 469   return 1;  /* continue running the coroutine */
 470 }
 471
 472
 473 /*
 474 ** signal an error in the call to 'resume', not in the execution of the
 475 ** coroutine itself. (Such errors should not be handled by any coroutine
 476 ** error handler and should not kill the coroutine.)
 477 */
 478 static l_noret resume_error (lua_State *L, const char *msg, StkId firstArg) {
 479   L->top = firstArg;  /* remove args from the stack */
 480   setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
 481   api_incr_top(L);
 482   luaD_throw(L, -1);  /* jump back to 'lua_resume' */
 483 }
 484
 485
 486 /*
 487 ** do the work for 'lua_resume' in protected mode
 488 */
 489 static void resume (lua_State *L, void *ud) {
 490   int nCcalls = L->nCcalls;
 491   StkId firstArg = cast(StkId, ud);
 492   CallInfo *ci = L->ci;
 493   if (nCcalls >= LUAI_MAXCCALLS)
 494     resume_error(L, "C stack overflow", firstArg);
 495   if (L->status == LUA_OK) {  /* may be starting a coroutine */
 496     if (ci != &L->base_ci)  /* not in base level? */
 497       resume_error(L, "cannot resume non-suspended coroutine", firstArg);
 498     /* coroutine is in base level; start running it */
 499     if (!luaD_precall(L, firstArg - 1, LUA_MULTRET))  /* Lua function? */
 500       luaV_execute(L);  /* call it */
 501   }
 502   else if (L->status != LUA_YIELD)
 503     resume_error(L, "cannot resume dead coroutine", firstArg);
 504   else {  /* resuming from previous yield */
 505     L->status = LUA_OK;
 506     ci->func = restorestack(L, ci->extra);
 507     if (isLua(ci))  /* yielded inside a hook? */
 508       luaV_execute(L);  /* just continue running Lua code */
 509     else {  /* 'common' yield */
 510       if (ci->u.c.k != NULL) {  /* does it have a continuation? */
 511         int n;
 512         ci->u.c.status = LUA_YIELD;  /* 'default' status */
 513         ci->callstatus |= CIST_YIELDED;
 514         lua_unlock(L);
 515         n = (*ci->u.c.k)(L);  /* call continuation */
 516         lua_lock(L);
 517         api_checknelems(L, n);
 518         firstArg = L->top - n;  /* yield results come from continuation */
 519       }
 520       luaD_poscall(L, firstArg);  /* finish 'luaD_precall' */
 521     }
 522     unroll(L, NULL);
 523   }
 524   lua_assert(nCcalls == L->nCcalls);
 525 }
 526
 527
 528 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
 529   int status;
 530   lua_lock(L);
 531   luai_userstateresume(L, nargs);
 532   L->nCcalls = (from) ? from->nCcalls + 1 : 1;
 533   L->nny = 0;  /* allow yields */
 534   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
 535   status = luaD_rawrunprotected(L, resume, L->top - nargs);
 536   if (status == -1)  /* error calling 'lua_resume'? */
 537     status = LUA_ERRRUN;
 538   else {  /* yield or regular error */
 539     while (status != LUA_OK && status != LUA_YIELD) {  /* error? */
 540       if (recover(L, status))  /* recover point? */
 541         status = luaD_rawrunprotected(L, unroll, NULL);  /* run continuation */
 542       else {  /* unrecoverable error */
 543         L->status = cast_byte(status);  /* mark thread as `dead' */
 544         seterrorobj(L, status, L->top);
 545         L->ci->top = L->top;
 546         break;
 547       }
 548     }
 549     lua_assert(status == L->status);
 550   }
 551   L->nny = 1;  /* do not allow yields */
 552   L->nCcalls--;
 553   lua_assert(L->nCcalls == ((from) ? from->nCcalls : 0));
 554   lua_unlock(L);
 555   return status;
 556 }
 557
 558
 559 LUA_API int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k) {
 560   CallInfo *ci = L->ci;
 561   luai_userstateyield(L, nresults);
 562   lua_lock(L);
 563   api_checknelems(L, nresults);
 564   if (L->nny > 0) {
 565     if (L != G(L)->mainthread)
 566       luaG_runerror(L, "attempt to yield across a C-call boundary");
 567     else
 568       luaG_runerror(L, "attempt to yield from outside a coroutine");
 569   }
 570   L->status = LUA_YIELD;
 571   ci->extra = savestack(L, ci->func);  /* save current 'func' */
 572   if (isLua(ci)) {  /* inside a hook? */
 573     api_check(L, k == NULL, "hooks cannot continue after yielding");
 574   }
 575   else {
 576     if ((ci->u.c.k = k) != NULL)  /* is there a continuation? */
 577       ci->u.c.ctx = ctx;  /* save context */
 578     ci->func = L->top - nresults - 1;  /* protect stack below results */
 579     luaD_throw(L, LUA_YIELD);
 580   }
 581   lua_assert(ci->callstatus & CIST_HOOKED);  /* must be inside a hook */
 582   lua_unlock(L);
 583   return 0;  /* return to 'luaD_hook' */
 584 }
 585
 586
 587 int luaD_pcall (lua_State *L, Pfunc func, void *u,
 588                 ptrdiff_t old_top, ptrdiff_t ef) {
 589   int status;
 590   CallInfo *old_ci = L->ci;
 591   lu_byte old_allowhooks = L->allowhook;
 592   unsigned short old_nny = L->nny;
 593   ptrdiff_t old_errfunc = L->errfunc;
 594   L->errfunc = ef;
 595   status = luaD_rawrunprotected(L, func, u);
 596   if (status != LUA_OK) {  /* an error occurred? */
 597     StkId oldtop = restorestack(L, old_top);
 598     luaF_close(L, oldtop);  /* close possible pending closures */
 599     seterrorobj(L, status, oldtop);
 600     L->ci = old_ci;
 601     L->allowhook = old_allowhooks;
 602     L->nny = old_nny;
 603     luaD_shrinkstack(L);
 604   }
 605   L->errfunc = old_errfunc;
 606   return status;
 607 }
 608
 609
 610
 611 /*
 612 ** Execute a protected parser.
 613 */
 614 struct SParser {  /* data to `f_parser' */
 615   ZIO *z;
 616   Mbuffer buff;  /* dynamic structure used by the scanner */
 617   Dyndata dyd;  /* dynamic structures used by the parser */
 618   const char *mode;
 619   const char *name;
 620 };
 621
 622
 623 static void checkmode (lua_State *L, const char *mode, const char *x) {
 624   if (mode && strchr(mode, x[0]) == NULL) {
 625     luaO_pushfstring(L,
 626        "attempt to load a %s chunk (mode is " LUA_QS ")", x, mode);
 627     luaD_throw(L, LUA_ERRSYNTAX);
 628   }
 629 }
 630
 631
 632 static void f_parser (lua_State *L, void *ud) {
 633   int i;
 634   Closure *cl;
 635   struct SParser *p = cast(struct SParser *, ud);
 636   int c = zgetc(p->z);  /* read first character */
 637   if (c == LUA_SIGNATURE[0]) {
 638     checkmode(L, p->mode, "binary");
 639     cl = luaU_undump(L, p->z, &p->buff, p->name);
 640   }
 641   else {
 642     checkmode(L, p->mode, "text");
 643     cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
 644   }
 645   lua_assert(cl->l.nupvalues == cl->l.p->sizeupvalues);
 646   for (i = 0; i < cl->l.nupvalues; i++) {  /* initialize upvalues */
 647     UpVal *up = luaF_newupval(L);
 648     cl->l.upvals[i] = up;
 649     luaC_objbarrier(L, cl, up);
 650   }
 651 }
 652
 653
 654 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 655                                         const char *mode) {
 656   struct SParser p;
 657   int status;
 658   L->nny++;  /* cannot yield during parsing */
 659   p.z = z; p.name = name; p.mode = mode;
 660   p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
 661   p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
 662   p.dyd.label.arr = NULL; p.dyd.label.size = 0;
 663   luaZ_initbuffer(L, &p.buff);
 664   status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
 665   luaZ_freebuffer(L, &p.buff);
 666   luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
 667   luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
 668   luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
 669   L->nny--;
 670   return status;
 671 }
 672
 673