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 /* Return the number of bytes available on the stack. */
  33 #if defined (_KERNEL) && defined(__linux__)
  34 #include <asm/current.h>
  35 static intptr_t stack_remaining(void) {
  36   char local;
  37   return (intptr_t)(&local - (char *)current->stack);
  38 }
  39 #elif defined (_KERNEL) && defined(__FreeBSD__)
  40 #include <sys/pcpu.h>
  41 static intptr_t stack_remaining(void) {
  42   char local;
  43   return (intptr_t)(&local - (char *)curthread->td_kstack);
  44 }
  45 #else
  46 static intptr_t stack_remaining(void) {
  47   return INTPTR_MAX;
  48 }
  49 #endif
  50
  51 /*
  52 ** {======================================================
  53 ** Error-recovery functions
  54 ** =======================================================
  55 */
  56
  57 /*
  58 ** LUAI_THROW/LUAI_TRY define how Lua does exception handling. By
  59 ** default, Lua handles errors with exceptions when compiling as
  60 ** C++ code, with _longjmp/_setjmp when asked to use them, and with
  61 ** longjmp/setjmp otherwise.
  62 */
  63 #if !defined(LUAI_THROW)
  64
  65 #ifdef _KERNEL
  66
  67 #ifdef __linux__
  68 #if defined(__i386__)
  69 #define JMP_BUF_CNT     6
  70 #elif defined(__x86_64__)
  71 #define JMP_BUF_CNT     8
  72 #elif defined(__sparc__) && defined(__arch64__)
  73 #define JMP_BUF_CNT     6
  74 #elif defined(__powerpc__)
  75 #define JMP_BUF_CNT     26
  76 #elif defined(__aarch64__)
  77 #define JMP_BUF_CNT     64
  78 #elif defined(__arm__)
  79 #define JMP_BUF_CNT     65
  80 #elif defined(__mips__)
  81 #define JMP_BUF_CNT     12
  82 #elif defined(__s390x__)
  83 #define JMP_BUF_CNT     18
  84 #elif defined(__riscv)
  85 #define JMP_BUF_CNT     64
  86 #else
  87 #define JMP_BUF_CNT     1
  88 #endif
  89
  90 typedef struct _label_t { long long unsigned val[JMP_BUF_CNT]; } label_t;
  91
  92 int setjmp(label_t *) __attribute__ ((__nothrow__));
  93 extern void longjmp(label_t *) __attribute__((__noreturn__));
  94
  95 #define LUAI_THROW(L,c)         longjmp(&(c)->b)
  96 #define LUAI_TRY(L,c,a)         if (setjmp(&(c)->b) == 0) { a }
  97 #define luai_jmpbuf             label_t
  98
  99 /* unsupported arches will build but not be able to run lua programs */
 100 #if JMP_BUF_CNT == 1
 101 int setjmp (label_t *buf) {
 102         return 1;
 103 }
 104
 105 void longjmp (label_t * buf) {
 106         for (;;);
 107 }
 108 #endif
 109 #else
 110 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
 111 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
 112 #define luai_jmpbuf             jmp_buf
 113 #endif
 114
 115 #else /* _KERNEL */
 116
 117 #if defined(__cplusplus) && !defined(LUA_USE_LONGJMP)
 118 /* C++ exceptions */
 119 #define LUAI_THROW(L,c)         throw(c)
 120 #define LUAI_TRY(L,c,a) \
 121         try { a } catch(...) { if ((c)->status == 0) (c)->status = -1; }
 122 #define luai_jmpbuf             int  /* dummy variable */
 123
 124 #elif defined(LUA_USE_ULONGJMP)
 125 /* in Unix, try _longjmp/_setjmp (more efficient) */
 126 #define LUAI_THROW(L,c)         _longjmp((c)->b, 1)
 127 #define LUAI_TRY(L,c,a)         if (_setjmp((c)->b) == 0) { a }
 128 #define luai_jmpbuf             jmp_buf
 129
 130 #else
 131 /* default handling with long jumps */
 132 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
 133 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
 134 #define luai_jmpbuf             jmp_buf
 135
 136 #endif
 137
 138 #endif /* _KERNEL */
 139
 140 #endif /* LUAI_THROW */
 141
 142
 143 /* chain list of long jump buffers */
 144 struct lua_longjmp {
 145   struct lua_longjmp *previous;
 146   luai_jmpbuf b;
 147   volatile int status;  /* error code */
 148 };
 149
 150
 151 static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
 152   switch (errcode) {
 153     case LUA_ERRMEM: {  /* memory error? */
 154       setsvalue2s(L, oldtop, G(L)->memerrmsg); /* reuse preregistered msg. */
 155       break;
 156     }
 157     case LUA_ERRERR: {
 158       setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
 159       break;
 160     }
 161     default: {
 162       setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
 163       break;
 164     }
 165   }
 166   L->top = oldtop + 1;
 167 }
 168
 169
 170 l_noret luaD_throw (lua_State *L, int errcode) {
 171   if (L->errorJmp) {  /* thread has an error handler? */
 172     L->errorJmp->status = errcode;  /* set status */
 173     LUAI_THROW(L, L->errorJmp);  /* jump to it */
 174   }
 175   else {  /* thread has no error handler */
 176     L->status = cast_byte(errcode);  /* mark it as dead */
 177     if (G(L)->mainthread->errorJmp) {  /* main thread has a handler? */
 178       setobjs2s(L, G(L)->mainthread->top++, L->top - 1);  /* copy error obj. */
 179       luaD_throw(G(L)->mainthread, errcode);  /* re-throw in main thread */
 180     }
 181     else {  /* no handler at all; abort */
 182       if (G(L)->panic) {  /* panic function? */
 183         lua_unlock(L);
 184         G(L)->panic(L);  /* call it (last chance to jump out) */
 185       }
 186       panic("no error handler");
 187     }
 188   }
 189 }
 190
 191
 192 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 193   unsigned short oldnCcalls = L->nCcalls;
 194   struct lua_longjmp lj;
 195   lj.status = LUA_OK;
 196   lj.previous = L->errorJmp;  /* chain new error handler */
 197   // cppcheck-suppress autoVariables
 198   L->errorJmp = &lj;
 199   LUAI_TRY(L, &lj,
 200     (*f)(L, ud);
 201   );
 202   L->errorJmp = lj.previous;  /* restore old error handler */
 203   L->nCcalls = oldnCcalls;
 204   return lj.status;
 205 }
 206
 207 /* }====================================================== */
 208
 209
 210 static void correctstack (lua_State *L, TValue *oldstack) {
 211   CallInfo *ci;
 212   GCObject *up;
 213   L->top = (L->top - oldstack) + L->stack;
 214   for (up = L->openupval; up != NULL; up = up->gch.next)
 215     gco2uv(up)->v = (gco2uv(up)->v - oldstack) + L->stack;
 216   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 217     ci->top = (ci->top - oldstack) + L->stack;
 218     ci->func = (ci->func - oldstack) + L->stack;
 219     if (isLua(ci))
 220       ci->u.l.base = (ci->u.l.base - oldstack) + L->stack;
 221   }
 222 }
 223
 224
 225 /* some space for error handling */
 226 #define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)
 227
 228
 229 void luaD_reallocstack (lua_State *L, int newsize) {
 230   TValue *oldstack = L->stack;
 231   int lim = L->stacksize;
 232   lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
 233   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
 234   luaM_reallocvector(L, L->stack, L->stacksize, newsize, TValue);
 235   for (; lim < newsize; lim++)
 236     setnilvalue(L->stack + lim); /* erase new segment */
 237   L->stacksize = newsize;
 238   L->stack_last = L->stack + newsize - EXTRA_STACK;
 239   correctstack(L, oldstack);
 240 }
 241
 242
 243 void luaD_growstack (lua_State *L, int n) {
 244   int size = L->stacksize;
 245   if (size > LUAI_MAXSTACK)  /* error after extra size? */
 246     luaD_throw(L, LUA_ERRERR);
 247   else {
 248     int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
 249     int newsize = 2 * size;
 250     if (newsize > LUAI_MAXSTACK) newsize = LUAI_MAXSTACK;
 251     if (newsize < needed) newsize = needed;
 252     if (newsize > LUAI_MAXSTACK) {  /* stack overflow? */
 253       luaD_reallocstack(L, ERRORSTACKSIZE);
 254       luaG_runerror(L, "stack overflow");
 255     }
 256     else
 257       luaD_reallocstack(L, newsize);
 258   }
 259 }
 260
 261
 262 static int stackinuse (lua_State *L) {
 263   CallInfo *ci;
 264   StkId lim = L->top;
 265   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 266     lua_assert(ci->top <= L->stack_last);
 267     if (lim < ci->top) lim = ci->top;
 268   }
 269   return cast_int(lim - L->stack) + 1;  /* part of stack in use */
 270 }
 271
 272
 273 void luaD_shrinkstack (lua_State *L) {
 274   int inuse = stackinuse(L);
 275   int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
 276   if (goodsize > LUAI_MAXSTACK) goodsize = LUAI_MAXSTACK;
 277   if (inuse > LUAI_MAXSTACK ||  /* handling stack overflow? */
 278       goodsize >= L->stacksize)  /* would grow instead of shrink? */
 279     condmovestack(L);  /* don't change stack (change only for debugging) */
 280   else
 281     luaD_reallocstack(L, goodsize);  /* shrink it */
 282 }
 283
 284
 285 void luaD_hook (lua_State *L, int event, int line) {
 286   lua_Hook hook = L->hook;
 287   if (hook && L->allowhook) {
 288     CallInfo *ci = L->ci;
 289     ptrdiff_t top = savestack(L, L->top);
 290     ptrdiff_t ci_top = savestack(L, ci->top);
 291     lua_Debug ar;
 292     ar.event = event;
 293     ar.currentline = line;
 294     ar.i_ci = ci;
 295     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 296     ci->top = L->top + LUA_MINSTACK;
 297     lua_assert(ci->top <= L->stack_last);
 298     L->allowhook = 0;  /* cannot call hooks inside a hook */
 299     ci->callstatus |= CIST_HOOKED;
 300     lua_unlock(L);
 301     (*hook)(L, &ar);
 302     lua_lock(L);
 303     lua_assert(!L->allowhook);
 304     L->allowhook = 1;
 305     ci->top = restorestack(L, ci_top);
 306     L->top = restorestack(L, top);
 307     ci->callstatus &= ~CIST_HOOKED;
 308   }
 309 }
 310
 311
 312 static void callhook (lua_State *L, CallInfo *ci) {
 313   int hook = LUA_HOOKCALL;
 314   ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */
 315   if (isLua(ci->previous) &&
 316       GET_OPCODE(*(ci->previous->u.l.savedpc - 1)) == OP_TAILCALL) {
 317     ci->callstatus |= CIST_TAIL;
 318     hook = LUA_HOOKTAILCALL;
 319   }
 320   luaD_hook(L, hook, -1);
 321   ci->u.l.savedpc--;  /* correct 'pc' */
 322 }
 323
 324
 325 static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
 326   int i;
 327   int nfixargs = p->numparams;
 328   StkId base, fixed;
 329   lua_assert(actual >= nfixargs);
 330   /* move fixed parameters to final position */
 331   luaD_checkstack(L, p->maxstacksize);  /* check again for new 'base' */
 332   fixed = L->top - actual;  /* first fixed argument */
 333   base = L->top;  /* final position of first argument */
 334   for (i=0; i<nfixargs; i++) {
 335     setobjs2s(L, L->top++, fixed + i);
 336     setnilvalue(fixed + i);
 337   }
 338   return base;
 339 }
 340
 341
 342 static StkId tryfuncTM (lua_State *L, StkId func) {
 343   const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
 344   StkId p;
 345   ptrdiff_t funcr = savestack(L, func);
 346   if (!ttisfunction(tm))
 347     luaG_typeerror(L, func, "call");
 348   /* Open a hole inside the stack at `func' */
 349   for (p = L->top; p > func; p--) setobjs2s(L, p, p-1);
 350   incr_top(L);
 351   func = restorestack(L, funcr);  /* previous call may change stack */
 352   setobj2s(L, func, tm);  /* tag method is the new function to be called */
 353   return func;
 354 }
 355
 356
 357
 358 #define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))
 359
 360
 361 /*
 362 ** returns true if function has been executed (C function)
 363 */
 364 int luaD_precall (lua_State *L, StkId func, int nresults) {
 365   lua_CFunction f;
 366   CallInfo *ci;
 367   int n;  /* number of arguments (Lua) or returns (C) */
 368   ptrdiff_t funcr = savestack(L, func);
 369   switch (ttype(func)) {
 370     case LUA_TLCF:  /* light C function */
 371       f = fvalue(func);
 372       goto Cfunc;
 373     case LUA_TCCL: {  /* C closure */
 374       f = clCvalue(func)->f;
 375      Cfunc:
 376       luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 377       ci = next_ci(L);  /* now 'enter' new function */
 378       ci->nresults = nresults;
 379       ci->func = restorestack(L, funcr);
 380       ci->top = L->top + LUA_MINSTACK;
 381       lua_assert(ci->top <= L->stack_last);
 382       ci->callstatus = 0;
 383       luaC_checkGC(L);  /* stack grow uses memory */
 384       if (L->hookmask & LUA_MASKCALL)
 385         luaD_hook(L, LUA_HOOKCALL, -1);
 386       lua_unlock(L);
 387       n = (*f)(L);  /* do the actual call */
 388       lua_lock(L);
 389       api_checknelems(L, n);
 390       luaD_poscall(L, L->top - n);
 391       return 1;
 392     }
 393     case LUA_TLCL: {  /* Lua function: prepare its call */
 394       StkId base;
 395       Proto *p = clLvalue(func)->p;
 396       n = cast_int(L->top - func) - 1;  /* number of real arguments */
 397       luaD_checkstack(L, p->maxstacksize);
 398       for (; n < p->numparams; n++)
 399         setnilvalue(L->top++);  /* complete missing arguments */
 400       if (!p->is_vararg) {
 401         func = restorestack(L, funcr);
 402         base = func + 1;
 403       }
 404       else {
 405         base = adjust_varargs(L, p, n);
 406         func = restorestack(L, funcr);  /* previous call can change stack */
 407       }
 408       ci = next_ci(L);  /* now 'enter' new function */
 409       ci->nresults = nresults;
 410       ci->func = func;
 411       ci->u.l.base = base;
 412       ci->top = base + p->maxstacksize;
 413       lua_assert(ci->top <= L->stack_last);
 414       ci->u.l.savedpc = p->code;  /* starting point */
 415       ci->callstatus = CIST_LUA;
 416       L->top = ci->top;
 417       luaC_checkGC(L);  /* stack grow uses memory */
 418       if (L->hookmask & LUA_MASKCALL)
 419         callhook(L, ci);
 420       return 0;
 421     }
 422     default: {  /* not a function */
 423       func = tryfuncTM(L, func);  /* retry with 'function' tag method */
 424       return luaD_precall(L, func, nresults);  /* now it must be a function */
 425     }
 426   }
 427 }
 428
 429
 430 int luaD_poscall (lua_State *L, StkId firstResult) {
 431   StkId res;
 432   int wanted, i;
 433   CallInfo *ci = L->ci;
 434   if (L->hookmask & (LUA_MASKRET | LUA_MASKLINE)) {
 435     if (L->hookmask & LUA_MASKRET) {
 436       ptrdiff_t fr = savestack(L, firstResult);  /* hook may change stack */
 437       luaD_hook(L, LUA_HOOKRET, -1);
 438       firstResult = restorestack(L, fr);
 439     }
 440     L->oldpc = ci->previous->u.l.savedpc;  /* 'oldpc' for caller function */
 441   }
 442   res = ci->func;  /* res == final position of 1st result */
 443   wanted = ci->nresults;
 444   L->ci = ci = ci->previous;  /* back to caller */
 445   /* move results to correct place */
 446   for (i = wanted; i != 0 && firstResult < L->top; i--)
 447     setobjs2s(L, res++, firstResult++);
 448   while (i-- > 0)
 449     setnilvalue(res++);
 450   L->top = res;
 451   return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
 452 }
 453
 454
 455 /*
 456 ** Call a function (C or Lua). The function to be called is at *func.
 457 ** The arguments are on the stack, right after the function.
 458 ** When returns, all the results are on the stack, starting at the original
 459 ** function position.
 460 */
 461 void luaD_call (lua_State *L, StkId func, int nResults, int allowyield) {
 462   if (++L->nCcalls >= LUAI_MAXCCALLS) {
 463     if (L->nCcalls == LUAI_MAXCCALLS)
 464       luaG_runerror(L, "C stack overflow");
 465     else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
 466       luaD_throw(L, LUA_ERRERR);  /* error while handling stack error */
 467   }
 468   intptr_t remaining = stack_remaining();
 469   if (L->runerror == 0 && remaining < LUAI_MINCSTACK)
 470     luaG_runerror(L, "C stack overflow");
 471   if (L->runerror != 0 && remaining < LUAI_MINCSTACK / 2)
 472     luaD_throw(L, LUA_ERRERR);  /* error while handling stack error */
 473   if (!allowyield) L->nny++;
 474   if (!luaD_precall(L, func, nResults))  /* is a Lua function? */
 475     luaV_execute(L);  /* call it */
 476   if (!allowyield) L->nny--;
 477   L->nCcalls--;
 478 }
 479
 480
 481 static void finishCcall (lua_State *L) {
 482   CallInfo *ci = L->ci;
 483   int n;
 484   lua_assert(ci->u.c.k != NULL);  /* must have a continuation */
 485   lua_assert(L->nny == 0);
 486   if (ci->callstatus & CIST_YPCALL) {  /* was inside a pcall? */
 487     ci->callstatus &= ~CIST_YPCALL;  /* finish 'lua_pcall' */
 488     L->errfunc = ci->u.c.old_errfunc;
 489   }
 490   /* finish 'lua_callk'/'lua_pcall' */
 491   adjustresults(L, ci->nresults);
 492   /* call continuation function */
 493   if (!(ci->callstatus & CIST_STAT))  /* no call status? */
 494     ci->u.c.status = LUA_YIELD;  /* 'default' status */
 495   lua_assert(ci->u.c.status != LUA_OK);
 496   ci->callstatus = (ci->callstatus & ~(CIST_YPCALL | CIST_STAT)) | CIST_YIELDED;
 497   lua_unlock(L);
 498   n = (*ci->u.c.k)(L);
 499   lua_lock(L);
 500   api_checknelems(L, n);
 501   /* finish 'luaD_precall' */
 502   luaD_poscall(L, L->top - n);
 503 }
 504
 505
 506 static void unroll (lua_State *L, void *ud) {
 507   UNUSED(ud);
 508   for (;;) {
 509     if (L->ci == &L->base_ci)  /* stack is empty? */
 510       return;  /* coroutine finished normally */
 511     if (!isLua(L->ci))  /* C function? */
 512       finishCcall(L);
 513     else {  /* Lua function */
 514       luaV_finishOp(L);  /* finish interrupted instruction */
 515       luaV_execute(L);  /* execute down to higher C 'boundary' */
 516     }
 517   }
 518 }
 519
 520
 521 /*
 522 ** check whether thread has a suspended protected call
 523 */
 524 static CallInfo *findpcall (lua_State *L) {
 525   CallInfo *ci;
 526   for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
 527     if (ci->callstatus & CIST_YPCALL)
 528       return ci;
 529   }
 530   return NULL;  /* no pending pcall */
 531 }
 532
 533
 534 static int recover (lua_State *L, int status) {
 535   StkId oldtop;
 536   CallInfo *ci = findpcall(L);
 537   if (ci == NULL) return 0;  /* no recovery point */
 538   /* "finish" luaD_pcall */
 539   oldtop = restorestack(L, ci->extra);
 540   luaF_close(L, oldtop);
 541   seterrorobj(L, status, oldtop);
 542   L->ci = ci;
 543   L->allowhook = ci->u.c.old_allowhook;
 544   L->nny = 0;  /* should be zero to be yieldable */
 545   luaD_shrinkstack(L);
 546   L->errfunc = ci->u.c.old_errfunc;
 547   ci->callstatus |= CIST_STAT;  /* call has error status */
 548   ci->u.c.status = status;  /* (here it is) */
 549   return 1;  /* continue running the coroutine */
 550 }
 551
 552
 553 /*
 554 ** signal an error in the call to 'resume', not in the execution of the
 555 ** coroutine itself. (Such errors should not be handled by any coroutine
 556 ** error handler and should not kill the coroutine.)
 557 */
 558 static l_noret resume_error (lua_State *L, const char *msg, StkId firstArg) {
 559   L->top = firstArg;  /* remove args from the stack */
 560   setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
 561   api_incr_top(L);
 562   luaD_throw(L, -1);  /* jump back to 'lua_resume' */
 563 }
 564
 565
 566 /*
 567 ** do the work for 'lua_resume' in protected mode
 568 */
 569 static void resume_cb (lua_State *L, void *ud) {
 570   int nCcalls = L->nCcalls;
 571   StkId firstArg = cast(StkId, ud);
 572   CallInfo *ci = L->ci;
 573   if (nCcalls >= LUAI_MAXCCALLS)
 574     resume_error(L, "C stack overflow", firstArg);
 575   if (L->status == LUA_OK) {  /* may be starting a coroutine */
 576     if (ci != &L->base_ci)  /* not in base level? */
 577       resume_error(L, "cannot resume non-suspended coroutine", firstArg);
 578     /* coroutine is in base level; start running it */
 579     if (!luaD_precall(L, firstArg - 1, LUA_MULTRET))  /* Lua function? */
 580       luaV_execute(L);  /* call it */
 581   }
 582   else if (L->status != LUA_YIELD)
 583     resume_error(L, "cannot resume dead coroutine", firstArg);
 584   else {  /* resuming from previous yield */
 585     L->status = LUA_OK;
 586     ci->func = restorestack(L, ci->extra);
 587     if (isLua(ci))  /* yielded inside a hook? */
 588       luaV_execute(L);  /* just continue running Lua code */
 589     else {  /* 'common' yield */
 590       if (ci->u.c.k != NULL) {  /* does it have a continuation? */
 591         int n;
 592         ci->u.c.status = LUA_YIELD;  /* 'default' status */
 593         ci->callstatus |= CIST_YIELDED;
 594         lua_unlock(L);
 595         n = (*ci->u.c.k)(L);  /* call continuation */
 596         lua_lock(L);
 597         api_checknelems(L, n);
 598         firstArg = L->top - n;  /* yield results come from continuation */
 599       }
 600       luaD_poscall(L, firstArg);  /* finish 'luaD_precall' */
 601     }
 602     unroll(L, NULL);
 603   }
 604   lua_assert(nCcalls == L->nCcalls);
 605 }
 606
 607
 608 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
 609   int status;
 610   int oldnny = L->nny;  /* save 'nny' */
 611   lua_lock(L);
 612   luai_userstateresume(L, nargs);
 613   L->nCcalls = (from) ? from->nCcalls + 1 : 1;
 614   L->nny = 0;  /* allow yields */
 615   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
 616   status = luaD_rawrunprotected(L, resume_cb, L->top - nargs);
 617   if (status == -1)  /* error calling 'lua_resume'? */
 618     status = LUA_ERRRUN;
 619   else {  /* yield or regular error */
 620     while (status != LUA_OK && status != LUA_YIELD) {  /* error? */
 621       if (recover(L, status))  /* recover point? */
 622         status = luaD_rawrunprotected(L, unroll, NULL);  /* run continuation */
 623       else {  /* unrecoverable error */
 624         L->status = cast_byte(status);  /* mark thread as `dead' */
 625         seterrorobj(L, status, L->top);
 626         L->ci->top = L->top;
 627         break;
 628       }
 629     }
 630     lua_assert(status == L->status);
 631   }
 632   L->nny = oldnny;  /* restore 'nny' */
 633   L->nCcalls--;
 634   lua_assert(L->nCcalls == ((from) ? from->nCcalls : 0));
 635   lua_unlock(L);
 636   return status;
 637 }
 638
 639
 640 LUA_API int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k) {
 641   CallInfo *ci = L->ci;
 642   luai_userstateyield(L, nresults);
 643   lua_lock(L);
 644   api_checknelems(L, nresults);
 645   if (L->nny > 0) {
 646     if (L != G(L)->mainthread)
 647       luaG_runerror(L, "attempt to yield across a C-call boundary");
 648     else
 649       luaG_runerror(L, "attempt to yield from outside a coroutine");
 650   }
 651   L->status = LUA_YIELD;
 652   ci->extra = savestack(L, ci->func);  /* save current 'func' */
 653   if (isLua(ci)) {  /* inside a hook? */
 654     api_check(L, k == NULL, "hooks cannot continue after yielding");
 655   }
 656   else {
 657     if ((ci->u.c.k = k) != NULL)  /* is there a continuation? */
 658       ci->u.c.ctx = ctx;  /* save context */
 659     ci->func = L->top - nresults - 1;  /* protect stack below results */
 660     luaD_throw(L, LUA_YIELD);
 661   }
 662   lua_assert(ci->callstatus & CIST_HOOKED);  /* must be inside a hook */
 663   lua_unlock(L);
 664   return 0;  /* return to 'luaD_hook' */
 665 }
 666
 667
 668 int luaD_pcall (lua_State *L, Pfunc func, void *u,
 669                 ptrdiff_t old_top, ptrdiff_t ef) {
 670   int status;
 671   CallInfo *old_ci = L->ci;
 672   lu_byte old_allowhooks = L->allowhook;
 673   unsigned short old_nny = L->nny;
 674   ptrdiff_t old_errfunc = L->errfunc;
 675   L->errfunc = ef;
 676   status = luaD_rawrunprotected(L, func, u);
 677   if (status != LUA_OK) {  /* an error occurred? */
 678     StkId oldtop = restorestack(L, old_top);
 679     luaF_close(L, oldtop);  /* close possible pending closures */
 680     seterrorobj(L, status, oldtop);
 681     L->ci = old_ci;
 682     L->allowhook = old_allowhooks;
 683     L->nny = old_nny;
 684     luaD_shrinkstack(L);
 685   }
 686   L->errfunc = old_errfunc;
 687   return status;
 688 }
 689
 690
 691
 692 /*
 693 ** Execute a protected parser.
 694 */
 695 struct SParser {  /* data to `f_parser' */
 696   ZIO *z;
 697   Mbuffer buff;  /* dynamic structure used by the scanner */
 698   Dyndata dyd;  /* dynamic structures used by the parser */
 699   const char *mode;
 700   const char *name;
 701 };
 702
 703
 704 static void checkmode (lua_State *L, const char *mode, const char *x) {
 705   if (mode && strchr(mode, x[0]) == NULL) {
 706     luaO_pushfstring(L,
 707        "attempt to load a %s chunk (mode is " LUA_QS ")", x, mode);
 708     luaD_throw(L, LUA_ERRSYNTAX);
 709   }
 710 }
 711
 712
 713 static void f_parser (lua_State *L, void *ud) {
 714   int i;
 715   Closure *cl;
 716   struct SParser *p = cast(struct SParser *, ud);
 717   int c = zgetc(p->z);  /* read first character */
 718   lua_assert(c != LUA_SIGNATURE[0]);    /* binary not supported */
 719   checkmode(L, p->mode, "text");
 720   cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
 721   lua_assert(cl->l.nupvalues == cl->l.p->sizeupvalues);
 722   for (i = 0; i < cl->l.nupvalues; i++) {  /* initialize upvalues */
 723     UpVal *up = luaF_newupval(L);
 724     cl->l.upvals[i] = up;
 725     luaC_objbarrier(L, cl, up);
 726   }
 727 }
 728
 729
 730 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 731                                         const char *mode) {
 732   struct SParser p;
 733   int status;
 734   L->nny++;  /* cannot yield during parsing */
 735   p.z = z; p.name = name; p.mode = mode;
 736   p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
 737   p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
 738   p.dyd.label.arr = NULL; p.dyd.label.size = 0;
 739   luaZ_initbuffer(L, &p.buff);
 740   status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
 741   luaZ_freebuffer(L, &p.buff);
 742   luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
 743   luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
 744   luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
 745   L->nny--;
 746   return status;
 747 }
 748 /* END CSTYLED */