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