module/lua/ldo.c

   1 /* BEGIN CSTYLED */
   2 /*
   3 ** $Id: ldo.c,v 2.108.1.3 2013/11/08 18:22:50 roberto Exp $
   4 ** Stack and Call structure of Lua
   5 ** See Copyright Notice in lua.h
   6 */
   7
   8
   9 #define ldo_c
  10 #define LUA_CORE
  11
  12 #include <sys/lua/lua.h>
  13
  14 #include "lapi.h"
  15 #include "ldebug.h"
  16 #include "ldo.h"
  17 #include "lfunc.h"
  18 #include "lgc.h"
  19 #include "lmem.h"
  20 #include "lobject.h"
  21 #include "lopcodes.h"
  22 #include "lparser.h"
  23 #include "lstate.h"
  24 #include "lstring.h"
  25 #include "ltable.h"
  26 #include "ltm.h"
  27 #include "lundump.h"
  28 #include "lvm.h"
  29 #include "lzio.h"
  30
  31
  32
  33
  34 /*
  35 ** {======================================================
  36 ** Error-recovery functions
  37 ** =======================================================
  38 */
  39
  40 /*
  41 ** LUAI_THROW/LUAI_TRY define how Lua does exception handling. By
  42 ** default, Lua handles errors with exceptions when compiling as
  43 ** C++ code, with _longjmp/_setjmp when asked to use them, and with
  44 ** longjmp/setjmp otherwise.
  45 */
  46 #if !defined(LUAI_THROW)
  47
  48 #ifdef _KERNEL
  49
  50 #if defined(__i386__)
  51 #define JMP_BUF_CNT     6
  52 #elif defined(__x86_64__)
  53 #define JMP_BUF_CNT     8
  54 #elif defined(__sparc__) && defined(__arch64__)
  55 #define JMP_BUF_CNT     6
  56 #elif defined(__powerpc__)
  57 #define JMP_BUF_CNT     26
  58 #elif defined(__aarch64__)
  59 #define JMP_BUF_CNT     64
  60 #elif defined(__arm__)
  61 #define JMP_BUF_CNT     65
  62 #elif defined(__mips__)
  63 #define JMP_BUF_CNT     12
  64 #elif defined(__s390x__)
  65 #define JMP_BUF_CNT     9
  66 #else
  67 #define JMP_BUF_CNT     1
  68 #endif
  69
  70 typedef struct _label_t { long long unsigned val[JMP_BUF_CNT]; } label_t;
  71
  72 int setjmp(label_t *) __attribute__ ((__nothrow__));
  73 extern void longjmp(label_t *) __attribute__((__noreturn__));
  74
  75 #define LUAI_THROW(L,c)         longjmp(&(c)->b)
  76 #define LUAI_TRY(L,c,a)         if (setjmp(&(c)->b) == 0) { a }
  77 #define luai_jmpbuf             label_t
  78
  79 /* unsupported archs will build but not be able to run lua programs */
  80 #if JMP_BUF_CNT == 1
  81 int setjmp (label_t *buf) {
  82         return 1;
  83 }
  84
  85 void longjmp (label_t * buf) {
  86         for (;;);
  87 }
  88 #endif
  89
  90 #else /* _KERNEL */
  91
  92 #if defined(__cplusplus) && !defined(LUA_USE_LONGJMP)
  93 /* C++ exceptions */
  94 #define LUAI_THROW(L,c)         throw(c)
  95 #define LUAI_TRY(L,c,a) \
  96         try { a } catch(...) { if ((c)->status == 0) (c)->status = -1; }
  97 #define luai_jmpbuf             int  /* dummy variable */
  98
  99 #elif defined(LUA_USE_ULONGJMP)
 100 /* in Unix, try _longjmp/_setjmp (more efficient) */
 101 #define LUAI_THROW(L,c)         _longjmp((c)->b, 1)
 102 #define LUAI_TRY(L,c,a)         if (_setjmp((c)->b) == 0) { a }
 103 #define luai_jmpbuf             jmp_buf
 104
 105 #else
 106 /* default handling with long jumps */
 107 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
 108 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
 109 #define luai_jmpbuf             jmp_buf
 110
 111 #endif
 112
 113 #endif /* _KERNEL */
 114
 115 #endif /* LUAI_THROW */
 116
 117
 118 /* chain list of long jump buffers */
 119 struct lua_longjmp {
 120   struct lua_longjmp *previous;
 121   luai_jmpbuf b;
 122   volatile int status;  /* error code */
 123 };
 124
 125
 126 static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
 127   switch (errcode) {
 128     case LUA_ERRMEM: {  /* memory error? */
 129       setsvalue2s(L, oldtop, G(L)->memerrmsg); /* reuse preregistered msg. */
 130       break;
 131     }
 132     case LUA_ERRERR: {
 133       setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
 134       break;
 135     }
 136     default: {
 137       setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
 138       break;
 139     }
 140   }
 141   L->top = oldtop + 1;
 142 }
 143
 144
 145 l_noret luaD_throw (lua_State *L, int errcode) {
 146   if (L->errorJmp) {  /* thread has an error handler? */
 147     L->errorJmp->status = errcode;  /* set status */
 148     LUAI_THROW(L, L->errorJmp);  /* jump to it */
 149   }
 150   else {  /* thread has no error handler */
 151     L->status = cast_byte(errcode);  /* mark it as dead */
 152     if (G(L)->mainthread->errorJmp) {  /* main thread has a handler? */
 153       setobjs2s(L, G(L)->mainthread->top++, L->top - 1);  /* copy error obj. */
 154       luaD_throw(G(L)->mainthread, errcode);  /* re-throw in main thread */
 155     }
 156     else {  /* no handler at all; abort */
 157       if (G(L)->panic) {  /* panic function? */
 158         lua_unlock(L);
 159         G(L)->panic(L);  /* call it (last chance to jump out) */
 160       }
 161       panic("no error handler");
 162     }
 163   }
 164 }
 165
 166
 167 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 168   unsigned short oldnCcalls = L->nCcalls;
 169   struct lua_longjmp lj;
 170   lj.status = LUA_OK;
 171   lj.previous = L->errorJmp;  /* chain new error handler */
 172   L->errorJmp = &lj;
 173   LUAI_TRY(L, &lj,
 174     (*f)(L, ud);
 175   );
 176   L->errorJmp = lj.previous;  /* restore old error handler */
 177   L->nCcalls = oldnCcalls;
 178   return lj.status;
 179 }
 180
 181 /* }====================================================== */
 182
 183
 184 static void correctstack (lua_State *L, TValue *oldstack) {
 185   CallInfo *ci;
 186   GCObject *up;
 187   L->top = (L->top - oldstack) + L->stack;
 188   for (up = L->openupval; up != NULL; up = up->gch.next)
 189     gco2uv(up)->v = (gco2uv(up)->v - oldstack) + L->stack;
 190   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 191     ci->top = (ci->top - oldstack) + L->stack;
 192     ci->func = (ci->func - oldstack) + L->stack;
 193     if (isLua(ci))
 194       ci->u.l.base = (ci->u.l.base - oldstack) + L->stack;
 195   }
 196 }
 197
 198
 199 /* some space for error handling */
 200 #define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)
 201
 202
 203 void luaD_reallocstack (lua_State *L, int newsize) {
 204   TValue *oldstack = L->stack;
 205   int lim = L->stacksize;
 206   lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
 207   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
 208   luaM_reallocvector(L, L->stack, L->stacksize, newsize, TValue);
 209   for (; lim < newsize; lim++)
 210     setnilvalue(L->stack + lim); /* erase new segment */
 211   L->stacksize = newsize;
 212   L->stack_last = L->stack + newsize - EXTRA_STACK;
 213   correctstack(L, oldstack);
 214 }
 215
 216
 217 void luaD_growstack (lua_State *L, int n) {
 218   int size = L->stacksize;
 219   if (size > LUAI_MAXSTACK)  /* error after extra size? */
 220     luaD_throw(L, LUA_ERRERR);
 221   else {
 222     int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
 223     int newsize = 2 * size;
 224     if (newsize > LUAI_MAXSTACK) newsize = LUAI_MAXSTACK;
 225     if (newsize < needed) newsize = needed;
 226     if (newsize > LUAI_MAXSTACK) {  /* stack overflow? */
 227       luaD_reallocstack(L, ERRORSTACKSIZE);
 228       luaG_runerror(L, "stack overflow");
 229     }
 230     else
 231       luaD_reallocstack(L, newsize);
 232   }
 233 }
 234
 235
 236 static int stackinuse (lua_State *L) {
 237   CallInfo *ci;
 238   StkId lim = L->top;
 239   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 240     lua_assert(ci->top <= L->stack_last);
 241     if (lim < ci->top) lim = ci->top;
 242   }
 243   return cast_int(lim - L->stack) + 1;  /* part of stack in use */
 244 }
 245
 246
 247 void luaD_shrinkstack (lua_State *L) {
 248   int inuse = stackinuse(L);
 249   int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
 250   if (goodsize > LUAI_MAXSTACK) goodsize = LUAI_MAXSTACK;
 251   if (inuse > LUAI_MAXSTACK ||  /* handling stack overflow? */
 252       goodsize >= L->stacksize)  /* would grow instead of shrink? */
 253     condmovestack(L);  /* don't change stack (change only for debugging) */
 254   else
 255     luaD_reallocstack(L, goodsize);  /* shrink it */
 256 }
 257
 258
 259 void luaD_hook (lua_State *L, int event, int line) {
 260   lua_Hook hook = L->hook;
 261   if (hook && L->allowhook) {
 262     CallInfo *ci = L->ci;
 263     ptrdiff_t top = savestack(L, L->top);
 264     ptrdiff_t ci_top = savestack(L, ci->top);
 265     lua_Debug ar;
 266     ar.event = event;
 267     ar.currentline = line;
 268     ar.i_ci = ci;
 269     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 270     ci->top = L->top + LUA_MINSTACK;
 271     lua_assert(ci->top <= L->stack_last);
 272     L->allowhook = 0;  /* cannot call hooks inside a hook */
 273     ci->callstatus |= CIST_HOOKED;
 274     lua_unlock(L);
 275     (*hook)(L, &ar);
 276     lua_lock(L);
 277     lua_assert(!L->allowhook);
 278     L->allowhook = 1;
 279     ci->top = restorestack(L, ci_top);
 280     L->top = restorestack(L, top);
 281     ci->callstatus &= ~CIST_HOOKED;
 282   }
 283 }
 284
 285
 286 static void callhook (lua_State *L, CallInfo *ci) {
 287   int hook = LUA_HOOKCALL;
 288   ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */
 289   if (isLua(ci->previous) &&
 290       GET_OPCODE(*(ci->previous->u.l.savedpc - 1)) == OP_TAILCALL) {
 291     ci->callstatus |= CIST_TAIL;
 292     hook = LUA_HOOKTAILCALL;
 293   }
 294   luaD_hook(L, hook, -1);
 295   ci->u.l.savedpc--;  /* correct 'pc' */
 296 }
 297
 298
 299 static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
 300   int i;
 301   int nfixargs = p->numparams;
 302   StkId base, fixed;
 303   lua_assert(actual >= nfixargs);
 304   /* move fixed parameters to final position */
 305   luaD_checkstack(L, p->maxstacksize);  /* check again for new 'base' */
 306   fixed = L->top - actual;  /* first fixed argument */
 307   base = L->top;  /* final position of first argument */
 308   for (i=0; i<nfixargs; i++) {
 309     setobjs2s(L, L->top++, fixed + i);
 310     setnilvalue(fixed + i);
 311   }
 312   return base;
 313 }
 314
 315
 316 static StkId tryfuncTM (lua_State *L, StkId func) {
 317   const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
 318   StkId p;
 319   ptrdiff_t funcr = savestack(L, func);
 320   if (!ttisfunction(tm))
 321     luaG_typeerror(L, func, "call");
 322   /* Open a hole inside the stack at `func' */
 323   for (p = L->top; p > func; p--) setobjs2s(L, p, p-1);
 324   incr_top(L);
 325   func = restorestack(L, funcr);  /* previous call may change stack */
 326   setobj2s(L, func, tm);  /* tag method is the new function to be called */
 327   return func;
 328 }
 329
 330
 331
 332 #define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))
 333
 334
 335 /*
 336 ** returns true if function has been executed (C function)
 337 */
 338 int luaD_precall (lua_State *L, StkId func, int nresults) {
 339   lua_CFunction f;
 340   CallInfo *ci;
 341   int n;  /* number of arguments (Lua) or returns (C) */
 342   ptrdiff_t funcr = savestack(L, func);
 343   switch (ttype(func)) {
 344     case LUA_TLCF:  /* light C function */
 345       f = fvalue(func);
 346       goto Cfunc;
 347     case LUA_TCCL: {  /* C closure */
 348       f = clCvalue(func)->f;
 349      Cfunc:
 350       luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 351       ci = next_ci(L);  /* now 'enter' new function */
 352       ci->nresults = nresults;
 353       ci->func = restorestack(L, funcr);
 354       ci->top = L->top + LUA_MINSTACK;
 355       lua_assert(ci->top <= L->stack_last);
 356       ci->callstatus = 0;
 357       luaC_checkGC(L);  /* stack grow uses memory */
 358       if (L->hookmask & LUA_MASKCALL)
 359         luaD_hook(L, LUA_HOOKCALL, -1);
 360       lua_unlock(L);
 361       n = (*f)(L);  /* do the actual call */
 362       lua_lock(L);
 363       api_checknelems(L, n);
 364       luaD_poscall(L, L->top - n);
 365       return 1;
 366     }
 367     case LUA_TLCL: {  /* Lua function: prepare its call */
 368       StkId base;
 369       Proto *p = clLvalue(func)->p;
 370       n = cast_int(L->top - func) - 1;  /* number of real arguments */
 371       luaD_checkstack(L, p->maxstacksize);
 372       for (; n < p->numparams; n++)
 373         setnilvalue(L->top++);  /* complete missing arguments */
 374       if (!p->is_vararg) {
 375         func = restorestack(L, funcr);
 376         base = func + 1;
 377       }
 378       else {
 379         base = adjust_varargs(L, p, n);
 380         func = restorestack(L, funcr);  /* previous call can change stack */
 381       }
 382       ci = next_ci(L);  /* now 'enter' new function */
 383       ci->nresults = nresults;
 384       ci->func = func;
 385       ci->u.l.base = base;
 386       ci->top = base + p->maxstacksize;
 387       lua_assert(ci->top <= L->stack_last);
 388       ci->u.l.savedpc = p->code;  /* starting point */
 389       ci->callstatus = CIST_LUA;
 390       L->top = ci->top;
 391       luaC_checkGC(L);  /* stack grow uses memory */
 392       if (L->hookmask & LUA_MASKCALL)
 393         callhook(L, ci);
 394       return 0;
 395     }
 396     default: {  /* not a function */
 397       func = tryfuncTM(L, func);  /* retry with 'function' tag method */
 398       return luaD_precall(L, func, nresults);  /* now it must be a function */
 399     }
 400   }
 401 }
 402
 403
 404 int luaD_poscall (lua_State *L, StkId firstResult) {
 405   StkId res;
 406   int wanted, i;
 407   CallInfo *ci = L->ci;
 408   if (L->hookmask & (LUA_MASKRET | LUA_MASKLINE)) {
 409     if (L->hookmask & LUA_MASKRET) {
 410       ptrdiff_t fr = savestack(L, firstResult);  /* hook may change stack */
 411       luaD_hook(L, LUA_HOOKRET, -1);
 412       firstResult = restorestack(L, fr);
 413     }
 414     L->oldpc = ci->previous->u.l.savedpc;  /* 'oldpc' for caller function */
 415   }
 416   res = ci->func;  /* res == final position of 1st result */
 417   wanted = ci->nresults;
 418   L->ci = ci = ci->previous;  /* back to caller */
 419   /* move results to correct place */
 420   for (i = wanted; i != 0 && firstResult < L->top; i--)
 421     setobjs2s(L, res++, firstResult++);
 422   while (i-- > 0)
 423     setnilvalue(res++);
 424   L->top = res;
 425   return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
 426 }
 427
 428
 429 /*
 430 ** Call a function (C or Lua). The function to be called is at *func.
 431 ** The arguments are on the stack, right after the function.
 432 ** When returns, all the results are on the stack, starting at the original
 433 ** function position.
 434 */
 435 void luaD_call (lua_State *L, StkId func, int nResults, int allowyield) {
 436   if (++L->nCcalls >= LUAI_MAXCCALLS) {
 437     if (L->nCcalls == LUAI_MAXCCALLS)
 438       luaG_runerror(L, "C stack overflow");
 439     else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
 440       luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
 441   }
 442   if (!allowyield) L->nny++;
 443   if (!luaD_precall(L, func, nResults))  /* is a Lua function? */
 444     luaV_execute(L);  /* call it */
 445   if (!allowyield) L->nny--;
 446   L->nCcalls--;
 447 }
 448
 449
 450 static void finishCcall (lua_State *L) {
 451   CallInfo *ci = L->ci;
 452   int n;
 453   lua_assert(ci->u.c.k != NULL);  /* must have a continuation */
 454   lua_assert(L->nny == 0);
 455   if (ci->callstatus & CIST_YPCALL) {  /* was inside a pcall? */
 456     ci->callstatus &= ~CIST_YPCALL;  /* finish 'lua_pcall' */
 457     L->errfunc = ci->u.c.old_errfunc;
 458   }
 459   /* finish 'lua_callk'/'lua_pcall' */
 460   adjustresults(L, ci->nresults);
 461   /* call continuation function */
 462   if (!(ci->callstatus & CIST_STAT))  /* no call status? */
 463     ci->u.c.status = LUA_YIELD;  /* 'default' status */
 464   lua_assert(ci->u.c.status != LUA_OK);
 465   ci->callstatus = (ci->callstatus & ~(CIST_YPCALL | CIST_STAT)) | CIST_YIELDED;
 466   lua_unlock(L);
 467   n = (*ci->u.c.k)(L);
 468   lua_lock(L);
 469   api_checknelems(L, n);
 470   /* finish 'luaD_precall' */
 471   luaD_poscall(L, L->top - n);
 472 }
 473
 474
 475 static void unroll (lua_State *L, void *ud) {
 476   UNUSED(ud);
 477   for (;;) {
 478     if (L->ci == &L->base_ci)  /* stack is empty? */
 479       return;  /* coroutine finished normally */
 480     if (!isLua(L->ci))  /* C function? */
 481       finishCcall(L);
 482     else {  /* Lua function */
 483       luaV_finishOp(L);  /* finish interrupted instruction */
 484       luaV_execute(L);  /* execute down to higher C 'boundary' */
 485     }
 486   }
 487 }
 488
 489
 490 /*
 491 ** check whether thread has a suspended protected call
 492 */
 493 static CallInfo *findpcall (lua_State *L) {
 494   CallInfo *ci;
 495   for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
 496     if (ci->callstatus & CIST_YPCALL)
 497       return ci;
 498   }
 499   return NULL;  /* no pending pcall */
 500 }
 501
 502
 503 static int recover (lua_State *L, int status) {
 504   StkId oldtop;
 505   CallInfo *ci = findpcall(L);
 506   if (ci == NULL) return 0;  /* no recovery point */
 507   /* "finish" luaD_pcall */
 508   oldtop = restorestack(L, ci->extra);
 509   luaF_close(L, oldtop);
 510   seterrorobj(L, status, oldtop);
 511   L->ci = ci;
 512   L->allowhook = ci->u.c.old_allowhook;
 513   L->nny = 0;  /* should be zero to be yieldable */
 514   luaD_shrinkstack(L);
 515   L->errfunc = ci->u.c.old_errfunc;
 516   ci->callstatus |= CIST_STAT;  /* call has error status */
 517   ci->u.c.status = status;  /* (here it is) */
 518   return 1;  /* continue running the coroutine */
 519 }
 520
 521
 522 /*
 523 ** signal an error in the call to 'resume', not in the execution of the
 524 ** coroutine itself. (Such errors should not be handled by any coroutine
 525 ** error handler and should not kill the coroutine.)
 526 */
 527 static l_noret resume_error (lua_State *L, const char *msg, StkId firstArg) {
 528   L->top = firstArg;  /* remove args from the stack */
 529   setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
 530   api_incr_top(L);
 531   luaD_throw(L, -1);  /* jump back to 'lua_resume' */
 532 }
 533
 534
 535 /*
 536 ** do the work for 'lua_resume' in protected mode
 537 */
 538 static void resume_cb (lua_State *L, void *ud) {
 539   int nCcalls = L->nCcalls;
 540   StkId firstArg = cast(StkId, ud);
 541   CallInfo *ci = L->ci;
 542   if (nCcalls >= LUAI_MAXCCALLS)
 543     resume_error(L, "C stack overflow", firstArg);
 544   if (L->status == LUA_OK) {  /* may be starting a coroutine */
 545     if (ci != &L->base_ci)  /* not in base level? */
 546       resume_error(L, "cannot resume non-suspended coroutine", firstArg);
 547     /* coroutine is in base level; start running it */
 548     if (!luaD_precall(L, firstArg - 1, LUA_MULTRET))  /* Lua function? */
 549       luaV_execute(L);  /* call it */
 550   }
 551   else if (L->status != LUA_YIELD)
 552     resume_error(L, "cannot resume dead coroutine", firstArg);
 553   else {  /* resuming from previous yield */
 554     L->status = LUA_OK;
 555     ci->func = restorestack(L, ci->extra);
 556     if (isLua(ci))  /* yielded inside a hook? */
 557       luaV_execute(L);  /* just continue running Lua code */
 558     else {  /* 'common' yield */
 559       if (ci->u.c.k != NULL) {  /* does it have a continuation? */
 560         int n;
 561         ci->u.c.status = LUA_YIELD;  /* 'default' status */
 562         ci->callstatus |= CIST_YIELDED;
 563         lua_unlock(L);
 564         n = (*ci->u.c.k)(L);  /* call continuation */
 565         lua_lock(L);
 566         api_checknelems(L, n);
 567         firstArg = L->top - n;  /* yield results come from continuation */
 568       }
 569       luaD_poscall(L, firstArg);  /* finish 'luaD_precall' */
 570     }
 571     unroll(L, NULL);
 572   }
 573   lua_assert(nCcalls == L->nCcalls);
 574 }
 575
 576
 577 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
 578   int status;
 579   int oldnny = L->nny;  /* save 'nny' */
 580   lua_lock(L);
 581   luai_userstateresume(L, nargs);
 582   L->nCcalls = (from) ? from->nCcalls + 1 : 1;
 583   L->nny = 0;  /* allow yields */
 584   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
 585   status = luaD_rawrunprotected(L, resume_cb, L->top - nargs);
 586   if (status == -1)  /* error calling 'lua_resume'? */
 587     status = LUA_ERRRUN;
 588   else {  /* yield or regular error */
 589     while (status != LUA_OK && status != LUA_YIELD) {  /* error? */
 590       if (recover(L, status))  /* recover point? */
 591         status = luaD_rawrunprotected(L, unroll, NULL);  /* run continuation */
 592       else {  /* unrecoverable error */
 593         L->status = cast_byte(status);  /* mark thread as `dead' */
 594         seterrorobj(L, status, L->top);
 595         L->ci->top = L->top;
 596         break;
 597       }
 598     }
 599     lua_assert(status == L->status);
 600   }
 601   L->nny = oldnny;  /* restore 'nny' */
 602   L->nCcalls--;
 603   lua_assert(L->nCcalls == ((from) ? from->nCcalls : 0));
 604   lua_unlock(L);
 605   return status;
 606 }
 607
 608
 609 LUA_API int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k) {
 610   CallInfo *ci = L->ci;
 611   luai_userstateyield(L, nresults);
 612   lua_lock(L);
 613   api_checknelems(L, nresults);
 614   if (L->nny > 0) {
 615     if (L != G(L)->mainthread)
 616       luaG_runerror(L, "attempt to yield across a C-call boundary");
 617     else
 618       luaG_runerror(L, "attempt to yield from outside a coroutine");
 619   }
 620   L->status = LUA_YIELD;
 621   ci->extra = savestack(L, ci->func);  /* save current 'func' */
 622   if (isLua(ci)) {  /* inside a hook? */
 623     api_check(L, k == NULL, "hooks cannot continue after yielding");
 624   }
 625   else {
 626     if ((ci->u.c.k = k) != NULL)  /* is there a continuation? */
 627       ci->u.c.ctx = ctx;  /* save context */
 628     ci->func = L->top - nresults - 1;  /* protect stack below results */
 629     luaD_throw(L, LUA_YIELD);
 630   }
 631   lua_assert(ci->callstatus & CIST_HOOKED);  /* must be inside a hook */
 632   lua_unlock(L);
 633   return 0;  /* return to 'luaD_hook' */
 634 }
 635
 636
 637 int luaD_pcall (lua_State *L, Pfunc func, void *u,
 638                 ptrdiff_t old_top, ptrdiff_t ef) {
 639   int status;
 640   CallInfo *old_ci = L->ci;
 641   lu_byte old_allowhooks = L->allowhook;
 642   unsigned short old_nny = L->nny;
 643   ptrdiff_t old_errfunc = L->errfunc;
 644   L->errfunc = ef;
 645   status = luaD_rawrunprotected(L, func, u);
 646   if (status != LUA_OK) {  /* an error occurred? */
 647     StkId oldtop = restorestack(L, old_top);
 648     luaF_close(L, oldtop);  /* close possible pending closures */
 649     seterrorobj(L, status, oldtop);
 650     L->ci = old_ci;
 651     L->allowhook = old_allowhooks;
 652     L->nny = old_nny;
 653     luaD_shrinkstack(L);
 654   }
 655   L->errfunc = old_errfunc;
 656   return status;
 657 }
 658
 659
 660
 661 /*
 662 ** Execute a protected parser.
 663 */
 664 struct SParser {  /* data to `f_parser' */
 665   ZIO *z;
 666   Mbuffer buff;  /* dynamic structure used by the scanner */
 667   Dyndata dyd;  /* dynamic structures used by the parser */
 668   const char *mode;
 669   const char *name;
 670 };
 671
 672
 673 static void checkmode (lua_State *L, const char *mode, const char *x) {
 674   if (mode && strchr(mode, x[0]) == NULL) {
 675     luaO_pushfstring(L,
 676        "attempt to load a %s chunk (mode is " LUA_QS ")", x, mode);
 677     luaD_throw(L, LUA_ERRSYNTAX);
 678   }
 679 }
 680
 681
 682 static void f_parser (lua_State *L, void *ud) {
 683   int i;
 684   Closure *cl;
 685   struct SParser *p = cast(struct SParser *, ud);
 686   int c = zgetc(p->z);  /* read first character */
 687   if (c == LUA_SIGNATURE[0]) {
 688     checkmode(L, p->mode, "binary");
 689     cl = luaU_undump(L, p->z, &p->buff, p->name);
 690   }
 691   else {
 692     checkmode(L, p->mode, "text");
 693     cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
 694   }
 695   lua_assert(cl->l.nupvalues == cl->l.p->sizeupvalues);
 696   for (i = 0; i < cl->l.nupvalues; i++) {  /* initialize upvalues */
 697     UpVal *up = luaF_newupval(L);
 698     cl->l.upvals[i] = up;
 699     luaC_objbarrier(L, cl, up);
 700   }
 701 }
 702
 703
 704 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 705                                         const char *mode) {
 706   struct SParser p;
 707   int status;
 708   L->nny++;  /* cannot yield during parsing */
 709   p.z = z; p.name = name; p.mode = mode;
 710   p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
 711   p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
 712   p.dyd.label.arr = NULL; p.dyd.label.size = 0;
 713   luaZ_initbuffer(L, &p.buff);
 714   status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
 715   luaZ_freebuffer(L, &p.buff);
 716   luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
 717   luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
 718   luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
 719   L->nny--;
 720   return status;
 721 }
 722 /* END CSTYLED */