kernel/fs/zfs/lua/ldo.c

   1 /*
   2 ** $Id: ldo.c,v 2.108.1.3 2013/11/08 18:22:50 roberto Exp $
   3 ** Stack and Call structure of Lua
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7
   8 #include <sys/zfs_context.h>
   9
  10 #define ldo_c
  11 #define LUA_CORE
  12
  13 #include "lua.h"
  14
  15 #include "lapi.h"
  16 #include "ldebug.h"
  17 #include "ldo.h"
  18 #include "lfunc.h"
  19 #include "lgc.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 #include "ltm.h"
  28 #include "lundump.h"
  29 #include "lvm.h"
  30 #include "lzio.h"
  31
  32
  33
  34
  35 /*
  36 ** {======================================================
  37 ** Error-recovery functions
  38 ** =======================================================
  39 */
  40
  41 /*
  42 ** LUAI_THROW/LUAI_TRY define how Lua does exception handling. By
  43 ** default, Lua handles errors with exceptions when compiling as
  44 ** C++ code, with _longjmp/_setjmp when asked to use them, and with
  45 ** longjmp/setjmp otherwise.
  46 */
  47 #if !defined(LUAI_THROW)
  48
  49 #ifdef _KERNEL
  50 #define LUAI_THROW(L,c)         longjmp(&(c)->b)
  51 #define LUAI_TRY(L,c,a)         if (setjmp(&(c)->b) == 0) { a }
  52 #define luai_jmpbuf             label_t
  53 #else
  54 #if defined(__cplusplus) && !defined(LUA_USE_LONGJMP)
  55 /* C++ exceptions */
  56 #define LUAI_THROW(L,c)         throw(c)
  57 #define LUAI_TRY(L,c,a) \
  58         try { a } catch(...) { if ((c)->status == 0) (c)->status = -1; }
  59 #define luai_jmpbuf             int  /* dummy variable */
  60
  61 #elif defined(LUA_USE_ULONGJMP)
  62 /* in Unix, try _longjmp/_setjmp (more efficient) */
  63 #define LUAI_THROW(L,c)         _longjmp((c)->b, 1)
  64 #define LUAI_TRY(L,c,a)         if (_setjmp((c)->b) == 0) { a }
  65 #define luai_jmpbuf             jmp_buf
  66
  67 #else
  68 /* default handling with long jumps */
  69 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
  70 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
  71 #define luai_jmpbuf             jmp_buf
  72
  73 #endif
  74
  75 #endif
  76
  77 #endif
  78
  79
  80 /* chain list of long jump buffers */
  81 struct lua_longjmp {
  82   struct lua_longjmp *previous;
  83   luai_jmpbuf b;
  84   volatile int status;  /* error code */
  85 };
  86
  87
  88 static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
  89   switch (errcode) {
  90     case LUA_ERRMEM: {  /* memory error? */
  91       setsvalue2s(L, oldtop, G(L)->memerrmsg); /* reuse preregistered msg. */
  92       break;
  93     }
  94     case LUA_ERRERR: {
  95       setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
  96       break;
  97     }
  98     default: {
  99       setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
 100       break;
 101     }
 102   }
 103   L->top = oldtop + 1;
 104 }
 105
 106
 107 l_noret luaD_throw (lua_State *L, int errcode) {
 108   if (L->errorJmp) {  /* thread has an error handler? */
 109     L->errorJmp->status = errcode;  /* set status */
 110     LUAI_THROW(L, L->errorJmp);  /* jump to it */
 111   }
 112   else {  /* thread has no error handler */
 113     L->status = cast_byte(errcode);  /* mark it as dead */
 114     if (G(L)->mainthread->errorJmp) {  /* main thread has a handler? */
 115       setobjs2s(L, G(L)->mainthread->top++, L->top - 1);  /* copy error obj. */
 116       luaD_throw(G(L)->mainthread, errcode);  /* re-throw in main thread */
 117     }
 118     else {  /* no handler at all; abort */
 119       if (G(L)->panic) {  /* panic function? */
 120         lua_unlock(L);
 121         G(L)->panic(L);  /* call it (last chance to jump out) */
 122       }
 123       panic("no error handler");
 124     }
 125   }
 126 }
 127
 128
 129 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 130   unsigned short oldnCcalls = L->nCcalls;
 131   struct lua_longjmp lj;
 132   lj.status = LUA_OK;
 133   lj.previous = L->errorJmp;  /* chain new error handler */
 134   L->errorJmp = &lj;
 135   LUAI_TRY(L, &lj,
 136     (*f)(L, ud);
 137   );
 138   L->errorJmp = lj.previous;  /* restore old error handler */
 139   L->nCcalls = oldnCcalls;
 140   return lj.status;
 141 }
 142
 143 /* }====================================================== */
 144
 145
 146 static void correctstack (lua_State *L, TValue *oldstack) {
 147   CallInfo *ci;
 148   GCObject *up;
 149   L->top = (L->top - oldstack) + L->stack;
 150   for (up = L->openupval; up != NULL; up = up->gch.next)
 151     gco2uv(up)->v = (gco2uv(up)->v - oldstack) + L->stack;
 152   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 153     ci->top = (ci->top - oldstack) + L->stack;
 154     ci->func = (ci->func - oldstack) + L->stack;
 155     if (isLua(ci))
 156       ci->u.l.base = (ci->u.l.base - oldstack) + L->stack;
 157   }
 158 }
 159
 160
 161 /* some space for error handling */
 162 #define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)
 163
 164
 165 void luaD_reallocstack (lua_State *L, int newsize) {
 166   TValue *oldstack = L->stack;
 167   int lim = L->stacksize;
 168   lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
 169   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
 170   luaM_reallocvector(L, L->stack, L->stacksize, newsize, TValue);
 171   for (; lim < newsize; lim++)
 172     setnilvalue(L->stack + lim); /* erase new segment */
 173   L->stacksize = newsize;
 174   L->stack_last = L->stack + newsize - EXTRA_STACK;
 175   correctstack(L, oldstack);
 176 }
 177
 178
 179 void luaD_growstack (lua_State *L, int n) {
 180   int size = L->stacksize;
 181   if (size > LUAI_MAXSTACK)  /* error after extra size? */
 182     luaD_throw(L, LUA_ERRERR);
 183   else {
 184     int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
 185     int newsize = 2 * size;
 186     if (newsize > LUAI_MAXSTACK) newsize = LUAI_MAXSTACK;
 187     if (newsize < needed) newsize = needed;
 188     if (newsize > LUAI_MAXSTACK) {  /* stack overflow? */
 189       luaD_reallocstack(L, ERRORSTACKSIZE);
 190       luaG_runerror(L, "stack overflow");
 191     }
 192     else
 193       luaD_reallocstack(L, newsize);
 194   }
 195 }
 196
 197
 198 static int stackinuse (lua_State *L) {
 199   CallInfo *ci;
 200   StkId lim = L->top;
 201   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 202     lua_assert(ci->top <= L->stack_last);
 203     if (lim < ci->top) lim = ci->top;
 204   }
 205   return cast_int(lim - L->stack) + 1;  /* part of stack in use */
 206 }
 207
 208
 209 void luaD_shrinkstack (lua_State *L) {
 210   int inuse = stackinuse(L);
 211   int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
 212   if (goodsize > LUAI_MAXSTACK) goodsize = LUAI_MAXSTACK;
 213   if (inuse > LUAI_MAXSTACK ||  /* handling stack overflow? */
 214       goodsize >= L->stacksize)  /* would grow instead of shrink? */
 215     condmovestack(L);  /* don't change stack (change only for debugging) */
 216   else
 217     luaD_reallocstack(L, goodsize);  /* shrink it */
 218 }
 219
 220
 221 void luaD_hook (lua_State *L, int event, int line) {
 222   lua_Hook hook = L->hook;
 223   if (hook && L->allowhook) {
 224     CallInfo *ci = L->ci;
 225     ptrdiff_t top = savestack(L, L->top);
 226     ptrdiff_t ci_top = savestack(L, ci->top);
 227     lua_Debug ar;
 228     ar.event = event;
 229     ar.currentline = line;
 230     ar.i_ci = ci;
 231     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 232     ci->top = L->top + LUA_MINSTACK;
 233     lua_assert(ci->top <= L->stack_last);
 234     L->allowhook = 0;  /* cannot call hooks inside a hook */
 235     ci->callstatus |= CIST_HOOKED;
 236     lua_unlock(L);
 237     (*hook)(L, &ar);
 238     lua_lock(L);
 239     lua_assert(!L->allowhook);
 240     L->allowhook = 1;
 241     ci->top = restorestack(L, ci_top);
 242     L->top = restorestack(L, top);
 243     ci->callstatus &= ~CIST_HOOKED;
 244   }
 245 }
 246
 247
 248 static void callhook (lua_State *L, CallInfo *ci) {
 249   int hook = LUA_HOOKCALL;
 250   ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */
 251   if (isLua(ci->previous) &&
 252       GET_OPCODE(*(ci->previous->u.l.savedpc - 1)) == OP_TAILCALL) {
 253     ci->callstatus |= CIST_TAIL;
 254     hook = LUA_HOOKTAILCALL;
 255   }
 256   luaD_hook(L, hook, -1);
 257   ci->u.l.savedpc--;  /* correct 'pc' */
 258 }
 259
 260
 261 static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
 262   int i;
 263   int nfixargs = p->numparams;
 264   StkId base, fixed;
 265   lua_assert(actual >= nfixargs);
 266   /* move fixed parameters to final position */
 267   luaD_checkstack(L, p->maxstacksize);  /* check again for new 'base' */
 268   fixed = L->top - actual;  /* first fixed argument */
 269   base = L->top;  /* final position of first argument */
 270   for (i=0; i<nfixargs; i++) {
 271     setobjs2s(L, L->top++, fixed + i);
 272     setnilvalue(fixed + i);
 273   }
 274   return base;
 275 }
 276
 277
 278 static StkId tryfuncTM (lua_State *L, StkId func) {
 279   const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
 280   StkId p;
 281   ptrdiff_t funcr = savestack(L, func);
 282   if (!ttisfunction(tm))
 283     luaG_typeerror(L, func, "call");
 284   /* Open a hole inside the stack at `func' */
 285   for (p = L->top; p > func; p--) setobjs2s(L, p, p-1);
 286   incr_top(L);
 287   func = restorestack(L, funcr);  /* previous call may change stack */
 288   setobj2s(L, func, tm);  /* tag method is the new function to be called */
 289   return func;
 290 }
 291
 292
 293
 294 #define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))
 295
 296
 297 /*
 298 ** returns true if function has been executed (C function)
 299 */
 300 int luaD_precall (lua_State *L, StkId func, int nresults) {
 301   lua_CFunction f;
 302   CallInfo *ci;
 303   int n;  /* number of arguments (Lua) or returns (C) */
 304   ptrdiff_t funcr = savestack(L, func);
 305   switch (ttype(func)) {
 306     case LUA_TLCF:  /* light C function */
 307       f = fvalue(func);
 308       goto Cfunc;
 309     case LUA_TCCL: {  /* C closure */
 310       f = clCvalue(func)->f;
 311      Cfunc:
 312       luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 313       ci = next_ci(L);  /* now 'enter' new function */
 314       ci->nresults = nresults;
 315       ci->func = restorestack(L, funcr);
 316       ci->top = L->top + LUA_MINSTACK;
 317       lua_assert(ci->top <= L->stack_last);
 318       ci->callstatus = 0;
 319       luaC_checkGC(L);  /* stack grow uses memory */
 320       if (L->hookmask & LUA_MASKCALL)
 321         luaD_hook(L, LUA_HOOKCALL, -1);
 322       lua_unlock(L);
 323       n = (*f)(L);  /* do the actual call */
 324       lua_lock(L);
 325       api_checknelems(L, n);
 326       luaD_poscall(L, L->top - n);
 327       return 1;
 328     }
 329     case LUA_TLCL: {  /* Lua function: prepare its call */
 330       StkId base;
 331       Proto *p = clLvalue(func)->p;
 332       n = cast_int(L->top - func) - 1;  /* number of real arguments */
 333       luaD_checkstack(L, p->maxstacksize);
 334       for (; n < p->numparams; n++)
 335         setnilvalue(L->top++);  /* complete missing arguments */
 336       if (!p->is_vararg) {
 337         func = restorestack(L, funcr);
 338         base = func + 1;
 339       }
 340       else {
 341         base = adjust_varargs(L, p, n);
 342         func = restorestack(L, funcr);  /* previous call can change stack */
 343       }
 344       ci = next_ci(L);  /* now 'enter' new function */
 345       ci->nresults = nresults;
 346       ci->func = func;
 347       ci->u.l.base = base;
 348       ci->top = base + p->maxstacksize;
 349       lua_assert(ci->top <= L->stack_last);
 350       ci->u.l.savedpc = p->code;  /* starting point */
 351       ci->callstatus = CIST_LUA;
 352       L->top = ci->top;
 353       luaC_checkGC(L);  /* stack grow uses memory */
 354       if (L->hookmask & LUA_MASKCALL)
 355         callhook(L, ci);
 356       return 0;
 357     }
 358     default: {  /* not a function */
 359       func = tryfuncTM(L, func);  /* retry with 'function' tag method */
 360       return luaD_precall(L, func, nresults);  /* now it must be a function */
 361     }
 362   }
 363 }
 364
 365
 366 int luaD_poscall (lua_State *L, StkId firstResult) {
 367   StkId res;
 368   int wanted, i;
 369   CallInfo *ci = L->ci;
 370   if (L->hookmask & (LUA_MASKRET | LUA_MASKLINE)) {
 371     if (L->hookmask & LUA_MASKRET) {
 372       ptrdiff_t fr = savestack(L, firstResult);  /* hook may change stack */
 373       luaD_hook(L, LUA_HOOKRET, -1);
 374       firstResult = restorestack(L, fr);
 375     }
 376     L->oldpc = ci->previous->u.l.savedpc;  /* 'oldpc' for caller function */
 377   }
 378   res = ci->func;  /* res == final position of 1st result */
 379   wanted = ci->nresults;
 380   L->ci = ci = ci->previous;  /* back to caller */
 381   /* move results to correct place */
 382   for (i = wanted; i != 0 && firstResult < L->top; i--)
 383     setobjs2s(L, res++, firstResult++);
 384   while (i-- > 0)
 385     setnilvalue(res++);
 386   L->top = res;
 387   return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
 388 }
 389
 390
 391 /*
 392 ** Call a function (C or Lua). The function to be called is at *func.
 393 ** The arguments are on the stack, right after the function.
 394 ** When returns, all the results are on the stack, starting at the original
 395 ** function position.
 396 */
 397 void luaD_call (lua_State *L, StkId func, int nResults, int allowyield) {
 398   if (++L->nCcalls >= LUAI_MAXCCALLS) {
 399     if (L->nCcalls == LUAI_MAXCCALLS)
 400       luaG_runerror(L, "C stack overflow");
 401     else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
 402       luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
 403   }
 404   if (!allowyield) L->nny++;
 405   if (!luaD_precall(L, func, nResults))  /* is a Lua function? */
 406     luaV_execute(L);  /* call it */
 407   if (!allowyield) L->nny--;
 408   L->nCcalls--;
 409 }
 410
 411
 412 static void finishCcall (lua_State *L) {
 413   CallInfo *ci = L->ci;
 414   int n;
 415   lua_assert(ci->u.c.k != NULL);  /* must have a continuation */
 416   lua_assert(L->nny == 0);
 417   if (ci->callstatus & CIST_YPCALL) {  /* was inside a pcall? */
 418     ci->callstatus &= ~CIST_YPCALL;  /* finish 'lua_pcall' */
 419     L->errfunc = ci->u.c.old_errfunc;
 420   }
 421   /* finish 'lua_callk'/'lua_pcall' */
 422   adjustresults(L, ci->nresults);
 423   /* call continuation function */
 424   if (!(ci->callstatus & CIST_STAT))  /* no call status? */
 425     ci->u.c.status = LUA_YIELD;  /* 'default' status */
 426   lua_assert(ci->u.c.status != LUA_OK);
 427   ci->callstatus = (ci->callstatus & ~(CIST_YPCALL | CIST_STAT)) | CIST_YIELDED;
 428   lua_unlock(L);
 429   n = (*ci->u.c.k)(L);
 430   lua_lock(L);
 431   api_checknelems(L, n);
 432   /* finish 'luaD_precall' */
 433   luaD_poscall(L, L->top - n);
 434 }
 435
 436
 437 static void unroll (lua_State *L, void *ud) {
 438   UNUSED(ud);
 439   for (;;) {
 440     if (L->ci == &L->base_ci)  /* stack is empty? */
 441       return;  /* coroutine finished normally */
 442     if (!isLua(L->ci))  /* C function? */
 443       finishCcall(L);
 444     else {  /* Lua function */
 445       luaV_finishOp(L);  /* finish interrupted instruction */
 446       luaV_execute(L);  /* execute down to higher C 'boundary' */
 447     }
 448   }
 449 }
 450
 451
 452 /*
 453 ** check whether thread has a suspended protected call
 454 */
 455 static CallInfo *findpcall (lua_State *L) {
 456   CallInfo *ci;
 457   for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
 458     if (ci->callstatus & CIST_YPCALL)
 459       return ci;
 460   }
 461   return NULL;  /* no pending pcall */
 462 }
 463
 464
 465 static int recover (lua_State *L, int status) {
 466   StkId oldtop;
 467   CallInfo *ci = findpcall(L);
 468   if (ci == NULL) return 0;  /* no recovery point */
 469   /* "finish" luaD_pcall */
 470   oldtop = restorestack(L, ci->extra);
 471   luaF_close(L, oldtop);
 472   seterrorobj(L, status, oldtop);
 473   L->ci = ci;
 474   L->allowhook = ci->u.c.old_allowhook;
 475   L->nny = 0;  /* should be zero to be yieldable */
 476   luaD_shrinkstack(L);
 477   L->errfunc = ci->u.c.old_errfunc;
 478   ci->callstatus |= CIST_STAT;  /* call has error status */
 479   ci->u.c.status = status;  /* (here it is) */
 480   return 1;  /* continue running the coroutine */
 481 }
 482
 483
 484 /*
 485 ** signal an error in the call to 'resume', not in the execution of the
 486 ** coroutine itself. (Such errors should not be handled by any coroutine
 487 ** error handler and should not kill the coroutine.)
 488 */
 489 static l_noret resume_error (lua_State *L, const char *msg, StkId firstArg) {
 490   L->top = firstArg;  /* remove args from the stack */
 491   setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
 492   api_incr_top(L);
 493   luaD_throw(L, -1);  /* jump back to 'lua_resume' */
 494 }
 495
 496
 497 /*
 498 ** do the work for 'lua_resume' in protected mode
 499 */
 500 static void resume_cb (lua_State *L, void *ud) {
 501   int nCcalls = L->nCcalls;
 502   StkId firstArg = cast(StkId, ud);
 503   CallInfo *ci = L->ci;
 504   if (nCcalls >= LUAI_MAXCCALLS)
 505     resume_error(L, "C stack overflow", firstArg);
 506   if (L->status == LUA_OK) {  /* may be starting a coroutine */
 507     if (ci != &L->base_ci)  /* not in base level? */
 508       resume_error(L, "cannot resume non-suspended coroutine", firstArg);
 509     /* coroutine is in base level; start running it */
 510     if (!luaD_precall(L, firstArg - 1, LUA_MULTRET))  /* Lua function? */
 511       luaV_execute(L);  /* call it */
 512   }
 513   else if (L->status != LUA_YIELD)
 514     resume_error(L, "cannot resume dead coroutine", firstArg);
 515   else {  /* resuming from previous yield */
 516     L->status = LUA_OK;
 517     ci->func = restorestack(L, ci->extra);
 518     if (isLua(ci))  /* yielded inside a hook? */
 519       luaV_execute(L);  /* just continue running Lua code */
 520     else {  /* 'common' yield */
 521       if (ci->u.c.k != NULL) {  /* does it have a continuation? */
 522         int n;
 523         ci->u.c.status = LUA_YIELD;  /* 'default' status */
 524         ci->callstatus |= CIST_YIELDED;
 525         lua_unlock(L);
 526         n = (*ci->u.c.k)(L);  /* call continuation */
 527         lua_lock(L);
 528         api_checknelems(L, n);
 529         firstArg = L->top - n;  /* yield results come from continuation */
 530       }
 531       luaD_poscall(L, firstArg);  /* finish 'luaD_precall' */
 532     }
 533     unroll(L, NULL);
 534   }
 535   lua_assert(nCcalls == L->nCcalls);
 536 }
 537
 538
 539 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
 540   int status;
 541   int oldnny = L->nny;  /* save 'nny' */
 542   lua_lock(L);
 543   luai_userstateresume(L, nargs);
 544   L->nCcalls = (from) ? from->nCcalls + 1 : 1;
 545   L->nny = 0;  /* allow yields */
 546   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
 547   status = luaD_rawrunprotected(L, resume_cb, L->top - nargs);
 548   if (status == -1)  /* error calling 'lua_resume'? */
 549     status = LUA_ERRRUN;
 550   else {  /* yield or regular error */
 551     while (status != LUA_OK && status != LUA_YIELD) {  /* error? */
 552       if (recover(L, status))  /* recover point? */
 553         status = luaD_rawrunprotected(L, unroll, NULL);  /* run continuation */
 554       else {  /* unrecoverable error */
 555         L->status = cast_byte(status);  /* mark thread as `dead' */
 556         seterrorobj(L, status, L->top);
 557         L->ci->top = L->top;
 558         break;
 559       }
 560     }
 561     lua_assert(status == L->status);
 562   }
 563   L->nny = oldnny;  /* restore 'nny' */
 564   L->nCcalls--;
 565   lua_assert(L->nCcalls == ((from) ? from->nCcalls : 0));
 566   lua_unlock(L);
 567   return status;
 568 }
 569
 570
 571 LUA_API int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k) {
 572   CallInfo *ci = L->ci;
 573   luai_userstateyield(L, nresults);
 574   lua_lock(L);
 575   api_checknelems(L, nresults);
 576   if (L->nny > 0) {
 577     if (L != G(L)->mainthread)
 578       luaG_runerror(L, "attempt to yield across a C-call boundary");
 579     else
 580       luaG_runerror(L, "attempt to yield from outside a coroutine");
 581   }
 582   L->status = LUA_YIELD;
 583   ci->extra = savestack(L, ci->func);  /* save current 'func' */
 584   if (isLua(ci)) {  /* inside a hook? */
 585     api_check(L, k == NULL, "hooks cannot continue after yielding");
 586   }
 587   else {
 588     if ((ci->u.c.k = k) != NULL)  /* is there a continuation? */
 589       ci->u.c.ctx = ctx;  /* save context */
 590     ci->func = L->top - nresults - 1;  /* protect stack below results */
 591     luaD_throw(L, LUA_YIELD);
 592   }
 593   lua_assert(ci->callstatus & CIST_HOOKED);  /* must be inside a hook */
 594   lua_unlock(L);
 595   return 0;  /* return to 'luaD_hook' */
 596 }
 597
 598
 599 int luaD_pcall (lua_State *L, Pfunc func, void *u,
 600                 ptrdiff_t old_top, ptrdiff_t ef) {
 601   int status;
 602   CallInfo *old_ci = L->ci;
 603   lu_byte old_allowhooks = L->allowhook;
 604   unsigned short old_nny = L->nny;
 605   ptrdiff_t old_errfunc = L->errfunc;
 606   L->errfunc = ef;
 607   status = luaD_rawrunprotected(L, func, u);
 608   if (status != LUA_OK) {  /* an error occurred? */
 609     StkId oldtop = restorestack(L, old_top);
 610     luaF_close(L, oldtop);  /* close possible pending closures */
 611     seterrorobj(L, status, oldtop);
 612     L->ci = old_ci;
 613     L->allowhook = old_allowhooks;
 614     L->nny = old_nny;
 615     luaD_shrinkstack(L);
 616   }
 617   L->errfunc = old_errfunc;
 618   return status;
 619 }
 620
 621
 622
 623 /*
 624 ** Execute a protected parser.
 625 */
 626 struct SParser {  /* data to `f_parser' */
 627   ZIO *z;
 628   Mbuffer buff;  /* dynamic structure used by the scanner */
 629   Dyndata dyd;  /* dynamic structures used by the parser */
 630   const char *mode;
 631   const char *name;
 632 };
 633
 634
 635 static void checkmode (lua_State *L, const char *mode, const char *x) {
 636   if (mode && strchr(mode, x[0]) == NULL) {
 637     luaO_pushfstring(L,
 638        "attempt to load a %s chunk (mode is " LUA_QS ")", x, mode);
 639     luaD_throw(L, LUA_ERRSYNTAX);
 640   }
 641 }
 642
 643
 644 static void f_parser (lua_State *L, void *ud) {
 645   int i;
 646   Closure *cl;
 647   struct SParser *p = cast(struct SParser *, ud);
 648   int c = zgetc(p->z);  /* read first character */
 649   if (c == LUA_SIGNATURE[0]) {
 650     checkmode(L, p->mode, "binary");
 651     cl = luaU_undump(L, p->z, &p->buff, p->name);
 652   }
 653   else {
 654     checkmode(L, p->mode, "text");
 655     cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
 656   }
 657   lua_assert(cl->l.nupvalues == cl->l.p->sizeupvalues);
 658   for (i = 0; i < cl->l.nupvalues; i++) {  /* initialize upvalues */
 659     UpVal *up = luaF_newupval(L);
 660     cl->l.upvals[i] = up;
 661     luaC_objbarrier(L, cl, up);
 662   }
 663 }
 664
 665
 666 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 667                                         const char *mode) {
 668   struct SParser p;
 669   int status;
 670   L->nny++;  /* cannot yield during parsing */
 671   p.z = z; p.name = name; p.mode = mode;
 672   p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
 673   p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
 674   p.dyd.label.arr = NULL; p.dyd.label.size = 0;
 675   luaZ_initbuffer(L, &p.buff);
 676   status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
 677   luaZ_freebuffer(L, &p.buff);
 678   luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
 679   luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
 680   luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
 681   L->nny--;
 682   return status;
 683 }
 684
 685