ceph/src/civetweb/src/third_party/lua-5.3.1/src/ldo.c

   1 /*
   2 ** $Id: ldo.c,v 2.138 2015/05/22 17:48:19 roberto Exp $
   3 ** Stack and Call structure of Lua
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7 #define ldo_c
   8 #define LUA_CORE
   9
  10 #include "lprefix.h"
  11
  12
  13 #include <setjmp.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16
  17 #include "lua.h"
  18
  19 #include "lapi.h"
  20 #include "ldebug.h"
  21 #include "ldo.h"
  22 #include "lfunc.h"
  23 #include "lgc.h"
  24 #include "lmem.h"
  25 #include "lobject.h"
  26 #include "lopcodes.h"
  27 #include "lparser.h"
  28 #include "lstate.h"
  29 #include "lstring.h"
  30 #include "ltable.h"
  31 #include "ltm.h"
  32 #include "lundump.h"
  33 #include "lvm.h"
  34 #include "lzio.h"
  35
  36
  37
  38 #define errorstatus(s)  ((s) > LUA_YIELD)
  39
  40
  41 /*
  42 ** {======================================================
  43 ** Error-recovery functions
  44 ** =======================================================
  45 */
  46
  47 /*
  48 ** LUAI_THROW/LUAI_TRY define how Lua does exception handling. By
  49 ** default, Lua handles errors with exceptions when compiling as
  50 ** C++ code, with _longjmp/_setjmp when asked to use them, and with
  51 ** longjmp/setjmp otherwise.
  52 */
  53 #if !defined(LUAI_THROW)                                /* { */
  54
  55 #if defined(__cplusplus) && !defined(LUA_USE_LONGJMP)   /* { */
  56
  57 /* C++ exceptions */
  58 #define LUAI_THROW(L,c)         throw(c)
  59 #define LUAI_TRY(L,c,a) \
  60         try { a } catch(...) { if ((c)->status == 0) (c)->status = -1; }
  61 #define luai_jmpbuf             int  /* dummy variable */
  62
  63 #elif defined(LUA_USE_POSIX)                            /* }{ */
  64
  65 /* in POSIX, try _longjmp/_setjmp (more efficient) */
  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 #else                                                   /* }{ */
  71
  72 /* ISO C handling with long jumps */
  73 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
  74 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
  75 #define luai_jmpbuf             jmp_buf
  76
  77 #endif                                                  /* } */
  78
  79 #endif                                                  /* } */
  80
  81
  82
  83 /* chain list of long jump buffers */
  84 struct lua_longjmp {
  85   struct lua_longjmp *previous;
  86   luai_jmpbuf b;
  87   volatile int status;  /* error code */
  88 };
  89
  90
  91 static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
  92   switch (errcode) {
  93     case LUA_ERRMEM: {  /* memory error? */
  94       setsvalue2s(L, oldtop, G(L)->memerrmsg); /* reuse preregistered msg. */
  95       break;
  96     }
  97     case LUA_ERRERR: {
  98       setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
  99       break;
 100     }
 101     default: {
 102       setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
 103       break;
 104     }
 105   }
 106   L->top = oldtop + 1;
 107 }
 108
 109
 110 l_noret luaD_throw (lua_State *L, int errcode) {
 111   if (L->errorJmp) {  /* thread has an error handler? */
 112     L->errorJmp->status = errcode;  /* set status */
 113     LUAI_THROW(L, L->errorJmp);  /* jump to it */
 114   }
 115   else {  /* thread has no error handler */
 116     global_State *g = G(L);
 117     L->status = cast_byte(errcode);  /* mark it as dead */
 118     if (g->mainthread->errorJmp) {  /* main thread has a handler? */
 119       setobjs2s(L, g->mainthread->top++, L->top - 1);  /* copy error obj. */
 120       luaD_throw(g->mainthread, errcode);  /* re-throw in main thread */
 121     }
 122     else {  /* no handler at all; abort */
 123       if (g->panic) {  /* panic function? */
 124         seterrorobj(L, errcode, L->top);  /* assume EXTRA_STACK */
 125         if (L->ci->top < L->top)
 126           L->ci->top = L->top;  /* pushing msg. can break this invariant */
 127         lua_unlock(L);
 128         g->panic(L);  /* call panic function (last chance to jump out) */
 129       }
 130       abort();
 131     }
 132   }
 133 }
 134
 135
 136 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 137   unsigned short oldnCcalls = L->nCcalls;
 138   struct lua_longjmp lj;
 139   lj.status = LUA_OK;
 140   lj.previous = L->errorJmp;  /* chain new error handler */
 141   L->errorJmp = &lj;
 142   LUAI_TRY(L, &lj,
 143     (*f)(L, ud);
 144   );
 145   L->errorJmp = lj.previous;  /* restore old error handler */
 146   L->nCcalls = oldnCcalls;
 147   return lj.status;
 148 }
 149
 150 /* }====================================================== */
 151
 152
 153 static void correctstack (lua_State *L, TValue *oldstack) {
 154   CallInfo *ci;
 155   UpVal *up;
 156   L->top = (L->top - oldstack) + L->stack;
 157   for (up = L->openupval; up != NULL; up = up->u.open.next)
 158     up->v = (up->v - oldstack) + L->stack;
 159   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 160     ci->top = (ci->top - oldstack) + L->stack;
 161     ci->func = (ci->func - oldstack) + L->stack;
 162     if (isLua(ci))
 163       ci->u.l.base = (ci->u.l.base - oldstack) + L->stack;
 164   }
 165 }
 166
 167
 168 /* some space for error handling */
 169 #define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)
 170
 171
 172 void luaD_reallocstack (lua_State *L, int newsize) {
 173   TValue *oldstack = L->stack;
 174   int lim = L->stacksize;
 175   lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
 176   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
 177   luaM_reallocvector(L, L->stack, L->stacksize, newsize, TValue);
 178   for (; lim < newsize; lim++)
 179     setnilvalue(L->stack + lim); /* erase new segment */
 180   L->stacksize = newsize;
 181   L->stack_last = L->stack + newsize - EXTRA_STACK;
 182   correctstack(L, oldstack);
 183 }
 184
 185
 186 void luaD_growstack (lua_State *L, int n) {
 187   int size = L->stacksize;
 188   if (size > LUAI_MAXSTACK)  /* error after extra size? */
 189     luaD_throw(L, LUA_ERRERR);
 190   else {
 191     int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
 192     int newsize = 2 * size;
 193     if (newsize > LUAI_MAXSTACK) newsize = LUAI_MAXSTACK;
 194     if (newsize < needed) newsize = needed;
 195     if (newsize > LUAI_MAXSTACK) {  /* stack overflow? */
 196       luaD_reallocstack(L, ERRORSTACKSIZE);
 197       luaG_runerror(L, "stack overflow");
 198     }
 199     else
 200       luaD_reallocstack(L, newsize);
 201   }
 202 }
 203
 204
 205 static int stackinuse (lua_State *L) {
 206   CallInfo *ci;
 207   StkId lim = L->top;
 208   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 209     lua_assert(ci->top <= L->stack_last);
 210     if (lim < ci->top) lim = ci->top;
 211   }
 212   return cast_int(lim - L->stack) + 1;  /* part of stack in use */
 213 }
 214
 215
 216 void luaD_shrinkstack (lua_State *L) {
 217   int inuse = stackinuse(L);
 218   int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
 219   if (goodsize > LUAI_MAXSTACK) goodsize = LUAI_MAXSTACK;
 220   if (L->stacksize > LUAI_MAXSTACK)  /* was handling stack overflow? */
 221     luaE_freeCI(L);  /* free all CIs (list grew because of an error) */
 222   else
 223     luaE_shrinkCI(L);  /* shrink list */
 224   if (inuse > LUAI_MAXSTACK ||  /* still handling stack overflow? */
 225       goodsize >= L->stacksize)  /* would grow instead of shrink? */
 226     condmovestack(L);  /* don't change stack (change only for debugging) */
 227   else
 228     luaD_reallocstack(L, goodsize);  /* shrink it */
 229 }
 230
 231
 232 void luaD_hook (lua_State *L, int event, int line) {
 233   lua_Hook hook = L->hook;
 234   if (hook && L->allowhook) {
 235     CallInfo *ci = L->ci;
 236     ptrdiff_t top = savestack(L, L->top);
 237     ptrdiff_t ci_top = savestack(L, ci->top);
 238     lua_Debug ar;
 239     ar.event = event;
 240     ar.currentline = line;
 241     ar.i_ci = ci;
 242     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 243     ci->top = L->top + LUA_MINSTACK;
 244     lua_assert(ci->top <= L->stack_last);
 245     L->allowhook = 0;  /* cannot call hooks inside a hook */
 246     ci->callstatus |= CIST_HOOKED;
 247     lua_unlock(L);
 248     (*hook)(L, &ar);
 249     lua_lock(L);
 250     lua_assert(!L->allowhook);
 251     L->allowhook = 1;
 252     ci->top = restorestack(L, ci_top);
 253     L->top = restorestack(L, top);
 254     ci->callstatus &= ~CIST_HOOKED;
 255   }
 256 }
 257
 258
 259 static void callhook (lua_State *L, CallInfo *ci) {
 260   int hook = LUA_HOOKCALL;
 261   ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */
 262   if (isLua(ci->previous) &&
 263       GET_OPCODE(*(ci->previous->u.l.savedpc - 1)) == OP_TAILCALL) {
 264     ci->callstatus |= CIST_TAIL;
 265     hook = LUA_HOOKTAILCALL;
 266   }
 267   luaD_hook(L, hook, -1);
 268   ci->u.l.savedpc--;  /* correct 'pc' */
 269 }
 270
 271
 272 static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
 273   int i;
 274   int nfixargs = p->numparams;
 275   StkId base, fixed;
 276   lua_assert(actual >= nfixargs);
 277   /* move fixed parameters to final position */
 278   luaD_checkstack(L, p->maxstacksize);  /* check again for new 'base' */
 279   fixed = L->top - actual;  /* first fixed argument */
 280   base = L->top;  /* final position of first argument */
 281   for (i=0; i<nfixargs; i++) {
 282     setobjs2s(L, L->top++, fixed + i);
 283     setnilvalue(fixed + i);
 284   }
 285   return base;
 286 }
 287
 288
 289 /*
 290 ** Check whether __call metafield of 'func' is a function. If so, put
 291 ** it in stack below original 'func' so that 'luaD_precall' can call
 292 ** it. Raise an error if __call metafield is not a function.
 293 */
 294 static void tryfuncTM (lua_State *L, StkId func) {
 295   const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
 296   StkId p;
 297   if (!ttisfunction(tm))
 298     luaG_typeerror(L, func, "call");
 299   /* Open a hole inside the stack at 'func' */
 300   for (p = L->top; p > func; p--)
 301     setobjs2s(L, p, p-1);
 302   L->top++;  /* slot ensured by caller */
 303   setobj2s(L, func, tm);  /* tag method is the new function to be called */
 304 }
 305
 306
 307
 308 #define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))
 309
 310
 311 /*
 312 ** returns true if function has been executed (C function)
 313 */
 314 int luaD_precall (lua_State *L, StkId func, int nresults) {
 315   lua_CFunction f;
 316   CallInfo *ci;
 317   int n;  /* number of arguments (Lua) or returns (C) */
 318   ptrdiff_t funcr = savestack(L, func);
 319   switch (ttype(func)) {
 320     case LUA_TLCF:  /* light C function */
 321       f = fvalue(func);
 322       goto Cfunc;
 323     case LUA_TCCL: {  /* C closure */
 324       f = clCvalue(func)->f;
 325      Cfunc:
 326       luaC_checkGC(L);  /* stack grow uses memory */
 327       luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 328       ci = next_ci(L);  /* now 'enter' new function */
 329       ci->nresults = nresults;
 330       ci->func = restorestack(L, funcr);
 331       ci->top = L->top + LUA_MINSTACK;
 332       lua_assert(ci->top <= L->stack_last);
 333       ci->callstatus = 0;
 334       if (L->hookmask & LUA_MASKCALL)
 335         luaD_hook(L, LUA_HOOKCALL, -1);
 336       lua_unlock(L);
 337       n = (*f)(L);  /* do the actual call */
 338       lua_lock(L);
 339       api_checknelems(L, n);
 340       luaD_poscall(L, L->top - n, n);
 341       return 1;
 342     }
 343     case LUA_TLCL: {  /* Lua function: prepare its call */
 344       StkId base;
 345       Proto *p = clLvalue(func)->p;
 346       n = cast_int(L->top - func) - 1;  /* number of real arguments */
 347       luaC_checkGC(L);  /* stack grow uses memory */
 348       luaD_checkstack(L, p->maxstacksize);
 349       for (; n < p->numparams; n++)
 350         setnilvalue(L->top++);  /* complete missing arguments */
 351       if (!p->is_vararg) {
 352         func = restorestack(L, funcr);
 353         base = func + 1;
 354       }
 355       else {
 356         base = adjust_varargs(L, p, n);
 357         func = restorestack(L, funcr);  /* previous call can change stack */
 358       }
 359       ci = next_ci(L);  /* now 'enter' new function */
 360       ci->nresults = nresults;
 361       ci->func = func;
 362       ci->u.l.base = base;
 363       ci->top = base + p->maxstacksize;
 364       lua_assert(ci->top <= L->stack_last);
 365       ci->u.l.savedpc = p->code;  /* starting point */
 366       ci->callstatus = CIST_LUA;
 367       L->top = ci->top;
 368       if (L->hookmask & LUA_MASKCALL)
 369         callhook(L, ci);
 370       return 0;
 371     }
 372     default: {  /* not a function */
 373       luaD_checkstack(L, 1);  /* ensure space for metamethod */
 374       func = restorestack(L, funcr);  /* previous call may change stack */
 375       tryfuncTM(L, func);  /* try to get '__call' metamethod */
 376       return luaD_precall(L, func, nresults);  /* now it must be a function */
 377     }
 378   }
 379 }
 380
 381
 382 int luaD_poscall (lua_State *L, StkId firstResult, int nres) {
 383   StkId res;
 384   int wanted, i;
 385   CallInfo *ci = L->ci;
 386   if (L->hookmask & (LUA_MASKRET | LUA_MASKLINE)) {
 387     if (L->hookmask & LUA_MASKRET) {
 388       ptrdiff_t fr = savestack(L, firstResult);  /* hook may change stack */
 389       luaD_hook(L, LUA_HOOKRET, -1);
 390       firstResult = restorestack(L, fr);
 391     }
 392     L->oldpc = ci->previous->u.l.savedpc;  /* 'oldpc' for caller function */
 393   }
 394   res = ci->func;  /* res == final position of 1st result */
 395   wanted = ci->nresults;
 396   L->ci = ci->previous;  /* back to caller */
 397   /* move results to correct place */
 398   for (i = wanted; i != 0 && nres-- > 0; i--)
 399     setobjs2s(L, res++, firstResult++);
 400   while (i-- > 0)
 401     setnilvalue(res++);
 402   L->top = res;
 403   return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
 404 }
 405
 406
 407 /*
 408 ** Call a function (C or Lua). The function to be called is at *func.
 409 ** The arguments are on the stack, right after the function.
 410 ** When returns, all the results are on the stack, starting at the original
 411 ** function position.
 412 */
 413 void luaD_call (lua_State *L, StkId func, int nResults, int allowyield) {
 414   if (++L->nCcalls >= LUAI_MAXCCALLS) {
 415     if (L->nCcalls == LUAI_MAXCCALLS)
 416       luaG_runerror(L, "C stack overflow");
 417     else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
 418       luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
 419   }
 420   if (!allowyield) L->nny++;
 421   if (!luaD_precall(L, func, nResults))  /* is a Lua function? */
 422     luaV_execute(L);  /* call it */
 423   if (!allowyield) L->nny--;
 424   L->nCcalls--;
 425 }
 426
 427
 428 /*
 429 ** Completes the execution of an interrupted C function, calling its
 430 ** continuation function.
 431 */
 432 static void finishCcall (lua_State *L, int status) {
 433   CallInfo *ci = L->ci;
 434   int n;
 435   /* must have a continuation and must be able to call it */
 436   lua_assert(ci->u.c.k != NULL && L->nny == 0);
 437   /* error status can only happen in a protected call */
 438   lua_assert((ci->callstatus & CIST_YPCALL) || status == LUA_YIELD);
 439   if (ci->callstatus & CIST_YPCALL) {  /* was inside a pcall? */
 440     ci->callstatus &= ~CIST_YPCALL;  /* finish 'lua_pcall' */
 441     L->errfunc = ci->u.c.old_errfunc;
 442   }
 443   /* finish 'lua_callk'/'lua_pcall'; CIST_YPCALL and 'errfunc' already
 444      handled */
 445   adjustresults(L, ci->nresults);
 446   /* call continuation function */
 447   lua_unlock(L);
 448   n = (*ci->u.c.k)(L, status, ci->u.c.ctx);
 449   lua_lock(L);
 450   api_checknelems(L, n);
 451   /* finish 'luaD_precall' */
 452   luaD_poscall(L, L->top - n, n);
 453 }
 454
 455
 456 /*
 457 ** Executes "full continuation" (everything in the stack) of a
 458 ** previously interrupted coroutine until the stack is empty (or another
 459 ** interruption long-jumps out of the loop). If the coroutine is
 460 ** recovering from an error, 'ud' points to the error status, which must
 461 ** be passed to the first continuation function (otherwise the default
 462 ** status is LUA_YIELD).
 463 */
 464 static void unroll (lua_State *L, void *ud) {
 465   if (ud != NULL)  /* error status? */
 466     finishCcall(L, *(int *)ud);  /* finish 'lua_pcallk' callee */
 467   while (L->ci != &L->base_ci) {  /* something in the stack */
 468     if (!isLua(L->ci))  /* C function? */
 469       finishCcall(L, LUA_YIELD);  /* complete its execution */
 470     else {  /* Lua function */
 471       luaV_finishOp(L);  /* finish interrupted instruction */
 472       luaV_execute(L);  /* execute down to higher C 'boundary' */
 473     }
 474   }
 475 }
 476
 477
 478 /*
 479 ** Try to find a suspended protected call (a "recover point") for the
 480 ** given thread.
 481 */
 482 static CallInfo *findpcall (lua_State *L) {
 483   CallInfo *ci;
 484   for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
 485     if (ci->callstatus & CIST_YPCALL)
 486       return ci;
 487   }
 488   return NULL;  /* no pending pcall */
 489 }
 490
 491
 492 /*
 493 ** Recovers from an error in a coroutine. Finds a recover point (if
 494 ** there is one) and completes the execution of the interrupted
 495 ** 'luaD_pcall'. If there is no recover point, returns zero.
 496 */
 497 static int recover (lua_State *L, int status) {
 498   StkId oldtop;
 499   CallInfo *ci = findpcall(L);
 500   if (ci == NULL) return 0;  /* no recovery point */
 501   /* "finish" luaD_pcall */
 502   oldtop = restorestack(L, ci->extra);
 503   luaF_close(L, oldtop);
 504   seterrorobj(L, status, oldtop);
 505   L->ci = ci;
 506   L->allowhook = getoah(ci->callstatus);  /* restore original 'allowhook' */
 507   L->nny = 0;  /* should be zero to be yieldable */
 508   luaD_shrinkstack(L);
 509   L->errfunc = ci->u.c.old_errfunc;
 510   return 1;  /* continue running the coroutine */
 511 }
 512
 513
 514 /*
 515 ** signal an error in the call to 'resume', not in the execution of the
 516 ** coroutine itself. (Such errors should not be handled by any coroutine
 517 ** error handler and should not kill the coroutine.)
 518 */
 519 static l_noret resume_error (lua_State *L, const char *msg, StkId firstArg) {
 520   L->top = firstArg;  /* remove args from the stack */
 521   setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
 522   api_incr_top(L);
 523   luaD_throw(L, -1);  /* jump back to 'lua_resume' */
 524 }
 525
 526
 527 /*
 528 ** Do the work for 'lua_resume' in protected mode. Most of the work
 529 ** depends on the status of the coroutine: initial state, suspended
 530 ** inside a hook, or regularly suspended (optionally with a continuation
 531 ** function), plus erroneous cases: non-suspended coroutine or dead
 532 ** coroutine.
 533 */
 534 static void resume (lua_State *L, void *ud) {
 535   int nCcalls = L->nCcalls;
 536   int n = *(cast(int*, ud));  /* number of arguments */
 537   StkId firstArg = L->top - n;  /* first argument */
 538   CallInfo *ci = L->ci;
 539   if (nCcalls >= LUAI_MAXCCALLS)
 540     resume_error(L, "C stack overflow", firstArg);
 541   if (L->status == LUA_OK) {  /* may be starting a coroutine */
 542     if (ci != &L->base_ci)  /* not in base level? */
 543       resume_error(L, "cannot resume non-suspended coroutine", firstArg);
 544     /* coroutine is in base level; start running it */
 545     if (!luaD_precall(L, firstArg - 1, LUA_MULTRET))  /* Lua function? */
 546       luaV_execute(L);  /* call it */
 547   }
 548   else if (L->status != LUA_YIELD)
 549     resume_error(L, "cannot resume dead coroutine", firstArg);
 550   else {  /* resuming from previous yield */
 551     L->status = LUA_OK;  /* mark that it is running (again) */
 552     ci->func = restorestack(L, ci->extra);
 553     if (isLua(ci))  /* yielded inside a hook? */
 554       luaV_execute(L);  /* just continue running Lua code */
 555     else {  /* 'common' yield */
 556       if (ci->u.c.k != NULL) {  /* does it have a continuation function? */
 557         lua_unlock(L);
 558         n = (*ci->u.c.k)(L, LUA_YIELD, ci->u.c.ctx); /* call continuation */
 559         lua_lock(L);
 560         api_checknelems(L, n);
 561         firstArg = L->top - n;  /* yield results come from continuation */
 562       }
 563       luaD_poscall(L, firstArg, n);  /* finish 'luaD_precall' */
 564     }
 565     unroll(L, NULL);  /* run continuation */
 566   }
 567   lua_assert(nCcalls == L->nCcalls);
 568 }
 569
 570
 571 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
 572   int status;
 573   int oldnny = L->nny;  /* save "number of non-yieldable" calls */
 574   lua_lock(L);
 575   luai_userstateresume(L, nargs);
 576   L->nCcalls = (from) ? from->nCcalls + 1 : 1;
 577   L->nny = 0;  /* allow yields */
 578   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
 579   status = luaD_rawrunprotected(L, resume, &nargs);
 580   if (status == -1)  /* error calling 'lua_resume'? */
 581     status = LUA_ERRRUN;
 582   else {  /* continue running after recoverable errors */
 583     while (errorstatus(status) && recover(L, status)) {
 584       /* unroll continuation */
 585       status = luaD_rawrunprotected(L, unroll, &status);
 586     }
 587     if (errorstatus(status)) {  /* unrecoverable error? */
 588       L->status = cast_byte(status);  /* mark thread as 'dead' */
 589       seterrorobj(L, status, L->top);  /* push error message */
 590       L->ci->top = L->top;
 591     }
 592     else lua_assert(status == L->status);  /* normal end or yield */
 593   }
 594   L->nny = oldnny;  /* restore 'nny' */
 595   L->nCcalls--;
 596   lua_assert(L->nCcalls == ((from) ? from->nCcalls : 0));
 597   lua_unlock(L);
 598   return status;
 599 }
 600
 601
 602 LUA_API int lua_isyieldable (lua_State *L) {
 603   return (L->nny == 0);
 604 }
 605
 606
 607 LUA_API int lua_yieldk (lua_State *L, int nresults, lua_KContext ctx,
 608                         lua_KFunction 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 '%s')", x, mode);
 676     luaD_throw(L, LUA_ERRSYNTAX);
 677   }
 678 }
 679
 680
 681 static void f_parser (lua_State *L, void *ud) {
 682   LClosure *cl;
 683   struct SParser *p = cast(struct SParser *, ud);
 684   int c = zgetc(p->z);  /* read first character */
 685   if (c == LUA_SIGNATURE[0]) {
 686     checkmode(L, p->mode, "binary");
 687     cl = luaU_undump(L, p->z, &p->buff, p->name);
 688   }
 689   else {
 690     checkmode(L, p->mode, "text");
 691     cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
 692   }
 693   lua_assert(cl->nupvalues == cl->p->sizeupvalues);
 694   luaF_initupvals(L, cl);
 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
 717