module/lua/ldo.c

   1 /*
   2 ** $Id: ldo.c,v 2.108.1.3 2013/11/08 18:22:50 roberto Exp $
   3 ** Stack and Call structure of Lua
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7
   8 #define ldo_c
   9 #define LUA_CORE
  10
  11 #include <sys/lua/lua.h>
  12 #include <sys/asm_linkage.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 /* Return the number of bytes available on the stack. */
  32 #if defined (_KERNEL) && defined(__linux__)
  33 #include <asm/current.h>
  34 static intptr_t stack_remaining(void) {
  35   intptr_t local;
  36   local = (intptr_t)&local - (intptr_t)current->stack;
  37   return local;
  38 }
  39 #elif defined (_KERNEL) && defined(__FreeBSD__)
  40 #include <sys/pcpu.h>
  41 static intptr_t stack_remaining(void) {
  42   intptr_t local;
  43   local = (intptr_t)&local - (intptr_t)curthread->td_kstack;
  44   return local;
  45 }
  46 #else
  47 static intptr_t stack_remaining(void) {
  48   return INTPTR_MAX;
  49 }
  50 #endif
  51
  52 /*
  53 ** {======================================================
  54 ** Error-recovery functions
  55 ** =======================================================
  56 */
  57
  58 /*
  59 ** LUAI_THROW/LUAI_TRY define how Lua does exception handling. By
  60 ** default, Lua handles errors with exceptions when compiling as
  61 ** C++ code, with _longjmp/_setjmp when asked to use them, and with
  62 ** longjmp/setjmp otherwise.
  63 */
  64 #if !defined(LUAI_THROW)
  65
  66 #ifdef _KERNEL
  67
  68 #ifdef __linux__
  69 #if defined(__i386__)
  70 #define JMP_BUF_CNT     6
  71 #elif defined(__x86_64__)
  72 #define JMP_BUF_CNT     8
  73 #elif defined(__sparc__) && defined(__arch64__)
  74 #define JMP_BUF_CNT     6
  75 #elif defined(__powerpc__)
  76 #define JMP_BUF_CNT     26
  77 #elif defined(__aarch64__)
  78 #define JMP_BUF_CNT     64
  79 #elif defined(__arm__)
  80 #define JMP_BUF_CNT     65
  81 #elif defined(__mips__)
  82 #define JMP_BUF_CNT     12
  83 #elif defined(__s390x__)
  84 #define JMP_BUF_CNT     18
  85 #elif defined(__riscv)
  86 #define JMP_BUF_CNT     64
  87 #elif defined(__loongarch_lp64)
  88 #define JMP_BUF_CNT     64
  89 #else
  90 #define JMP_BUF_CNT     1
  91 #endif
  92
  93 typedef struct _label_t { long long unsigned val[JMP_BUF_CNT]; } label_t;
  94
  95 int ASMABI setjmp(label_t *) __attribute__ ((__nothrow__));
  96 extern __attribute__((noreturn)) void ASMABI longjmp(label_t *);
  97
  98 #define LUAI_THROW(L,c)         longjmp(&(c)->b)
  99 #define LUAI_TRY(L,c,a)         if (setjmp(&(c)->b) == 0) { a }
 100 #define luai_jmpbuf             label_t
 101
 102 /* unsupported arches will build but not be able to run lua programs */
 103 #if JMP_BUF_CNT == 1
 104 int setjmp (label_t *buf) {
 105         return 1;
 106 }
 107
 108 void longjmp (label_t * buf) {
 109         for (;;);
 110 }
 111 #endif
 112 #else
 113 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
 114 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
 115 #define luai_jmpbuf             jmp_buf
 116 #endif
 117
 118 #else /* _KERNEL */
 119
 120 #if defined(__cplusplus) && !defined(LUA_USE_LONGJMP)
 121 /* C++ exceptions */
 122 #define LUAI_THROW(L,c)         throw(c)
 123 #define LUAI_TRY(L,c,a) \
 124         try { a } catch(...) { if ((c)->status == 0) (c)->status = -1; }
 125 #define luai_jmpbuf             int  /* dummy variable */
 126
 127 #elif defined(LUA_USE_ULONGJMP)
 128 /* in Unix, try _longjmp/_setjmp (more efficient) */
 129 #define LUAI_THROW(L,c)         _longjmp((c)->b, 1)
 130 #define LUAI_TRY(L,c,a)         if (_setjmp((c)->b) == 0) { a }
 131 #define luai_jmpbuf             jmp_buf
 132
 133 #else
 134 /* default handling with long jumps */
 135 #define LUAI_THROW(L,c)         longjmp((c)->b, 1)
 136 #define LUAI_TRY(L,c,a)         if (setjmp((c)->b) == 0) { a }
 137 #define luai_jmpbuf             jmp_buf
 138
 139 #endif
 140
 141 #endif /* _KERNEL */
 142
 143 #endif /* LUAI_THROW */
 144
 145
 146 /* chain list of long jump buffers */
 147 struct lua_longjmp {
 148   struct lua_longjmp *previous;
 149   luai_jmpbuf b;
 150   volatile int status;  /* error code */
 151 };
 152
 153
 154 static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
 155   switch (errcode) {
 156     case LUA_ERRMEM: {  /* memory error? */
 157       setsvalue2s(L, oldtop, G(L)->memerrmsg); /* reuse preregistered msg. */
 158       break;
 159     }
 160     case LUA_ERRERR: {
 161       setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
 162       break;
 163     }
 164     default: {
 165       setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
 166       break;
 167     }
 168   }
 169   L->top = oldtop + 1;
 170 }
 171
 172 /*
 173  * Silence infinite recursion warning which was added to -Wall in gcc 12.1
 174  */
 175 #if defined(__GNUC__) && !defined(__clang__) && \
 176         defined(HAVE_KERNEL_INFINITE_RECURSION)
 177 #pragma GCC diagnostic push
 178 #pragma GCC diagnostic ignored "-Winfinite-recursion"
 179 #endif
 180
 181 l_noret luaD_throw (lua_State *L, int errcode) {
 182   if (L->errorJmp) {  /* thread has an error handler? */
 183     L->errorJmp->status = errcode;  /* set status */
 184     LUAI_THROW(L, L->errorJmp);  /* jump to it */
 185   }
 186   else {  /* thread has no error handler */
 187     L->status = cast_byte(errcode);  /* mark it as dead */
 188     if (G(L)->mainthread->errorJmp) {  /* main thread has a handler? */
 189       setobjs2s(L, G(L)->mainthread->top++, L->top - 1);  /* copy error obj. */
 190       luaD_throw(G(L)->mainthread, errcode);  /* re-throw in main thread */
 191     }
 192     else {  /* no handler at all; abort */
 193       if (G(L)->panic) {  /* panic function? */
 194         lua_unlock(L);
 195         G(L)->panic(L);  /* call it (last chance to jump out) */
 196       }
 197       panic("no error handler");
 198     }
 199   }
 200 }
 201
 202 #if defined(__GNUC__) && !defined(__clang__) && \
 203         defined(HAVE_INFINITE_RECURSION)
 204 #pragma GCC diagnostic pop
 205 #endif
 206
 207
 208 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 209   unsigned short oldnCcalls = L->nCcalls;
 210   struct lua_longjmp lj;
 211   lj.status = LUA_OK;
 212   lj.previous = L->errorJmp;  /* chain new error handler */
 213   L->errorJmp = &lj;
 214   LUAI_TRY(L, &lj,
 215     (*f)(L, ud);
 216   );
 217   L->errorJmp = lj.previous;  /* restore old error handler */
 218   L->nCcalls = oldnCcalls;
 219   return lj.status;
 220 }
 221
 222 /* }====================================================== */
 223
 224
 225 static void correctstack (lua_State *L, TValue *oldstack) {
 226   CallInfo *ci;
 227   GCObject *up;
 228   L->top = (L->top - oldstack) + L->stack;
 229   for (up = L->openupval; up != NULL; up = up->gch.next)
 230     gco2uv(up)->v = (gco2uv(up)->v - oldstack) + L->stack;
 231   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 232     ci->top = (ci->top - oldstack) + L->stack;
 233     ci->func = (ci->func - oldstack) + L->stack;
 234     if (isLua(ci))
 235       ci->u.l.base = (ci->u.l.base - oldstack) + L->stack;
 236   }
 237 }
 238
 239
 240 /* some space for error handling */
 241 #define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)
 242
 243
 244 void luaD_reallocstack (lua_State *L, int newsize) {
 245   TValue *oldstack = L->stack;
 246   int lim = L->stacksize;
 247   lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
 248   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
 249   luaM_reallocvector(L, L->stack, L->stacksize, newsize, TValue);
 250   for (; lim < newsize; lim++)
 251     setnilvalue(L->stack + lim); /* erase new segment */
 252   L->stacksize = newsize;
 253   L->stack_last = L->stack + newsize - EXTRA_STACK;
 254   correctstack(L, oldstack);
 255 }
 256
 257
 258 void luaD_growstack (lua_State *L, int n) {
 259   int size = L->stacksize;
 260   if (size > LUAI_MAXSTACK)  /* error after extra size? */
 261     luaD_throw(L, LUA_ERRERR);
 262   else {
 263     int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
 264     int newsize = 2 * size;
 265     if (newsize > LUAI_MAXSTACK) newsize = LUAI_MAXSTACK;
 266     if (newsize < needed) newsize = needed;
 267     if (newsize > LUAI_MAXSTACK) {  /* stack overflow? */
 268       luaD_reallocstack(L, ERRORSTACKSIZE);
 269       luaG_runerror(L, "stack overflow");
 270     }
 271     else
 272       luaD_reallocstack(L, newsize);
 273   }
 274 }
 275
 276
 277 static int stackinuse (lua_State *L) {
 278   CallInfo *ci;
 279   StkId lim = L->top;
 280   for (ci = L->ci; ci != NULL; ci = ci->previous) {
 281     lua_assert(ci->top <= L->stack_last);
 282     if (lim < ci->top) lim = ci->top;
 283   }
 284   return cast_int(lim - L->stack) + 1;  /* part of stack in use */
 285 }
 286
 287
 288 void luaD_shrinkstack (lua_State *L) {
 289   int inuse = stackinuse(L);
 290   int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
 291   if (goodsize > LUAI_MAXSTACK) goodsize = LUAI_MAXSTACK;
 292   if (inuse > LUAI_MAXSTACK ||  /* handling stack overflow? */
 293       goodsize >= L->stacksize)  /* would grow instead of shrink? */
 294     condmovestack(L);  /* don't change stack (change only for debugging) */
 295   else
 296     luaD_reallocstack(L, goodsize);  /* shrink it */
 297 }
 298
 299
 300 void luaD_hook (lua_State *L, int event, int line) {
 301   lua_Hook hook = L->hook;
 302   if (hook && L->allowhook) {
 303     CallInfo *ci = L->ci;
 304     ptrdiff_t top = savestack(L, L->top);
 305     ptrdiff_t ci_top = savestack(L, ci->top);
 306     lua_Debug ar;
 307     ar.event = event;
 308     ar.currentline = line;
 309     ar.i_ci = ci;
 310     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 311     ci->top = L->top + LUA_MINSTACK;
 312     lua_assert(ci->top <= L->stack_last);
 313     L->allowhook = 0;  /* cannot call hooks inside a hook */
 314     ci->callstatus |= CIST_HOOKED;
 315     lua_unlock(L);
 316     (*hook)(L, &ar);
 317     lua_lock(L);
 318     lua_assert(!L->allowhook);
 319     L->allowhook = 1;
 320     ci->top = restorestack(L, ci_top);
 321     L->top = restorestack(L, top);
 322     ci->callstatus &= ~CIST_HOOKED;
 323   }
 324 }
 325
 326
 327 static void callhook (lua_State *L, CallInfo *ci) {
 328   int hook = LUA_HOOKCALL;
 329   ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */
 330   if (isLua(ci->previous) &&
 331       GET_OPCODE(*(ci->previous->u.l.savedpc - 1)) == OP_TAILCALL) {
 332     ci->callstatus |= CIST_TAIL;
 333     hook = LUA_HOOKTAILCALL;
 334   }
 335   luaD_hook(L, hook, -1);
 336   ci->u.l.savedpc--;  /* correct 'pc' */
 337 }
 338
 339
 340 static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
 341   int i;
 342   int nfixargs = p->numparams;
 343   StkId base, fixed;
 344   lua_assert(actual >= nfixargs);
 345   /* move fixed parameters to final position */
 346   luaD_checkstack(L, p->maxstacksize);  /* check again for new 'base' */
 347   fixed = L->top - actual;  /* first fixed argument */
 348   base = L->top;  /* final position of first argument */
 349   for (i=0; i<nfixargs; i++) {
 350     setobjs2s(L, L->top++, fixed + i);
 351     setnilvalue(fixed + i);
 352   }
 353   return base;
 354 }
 355
 356
 357 static StkId tryfuncTM (lua_State *L, StkId func) {
 358   const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
 359   StkId p;
 360   ptrdiff_t funcr = savestack(L, func);
 361   if (!ttisfunction(tm))
 362     luaG_typeerror(L, func, "call");
 363   /* Open a hole inside the stack at `func' */
 364   for (p = L->top; p > func; p--) setobjs2s(L, p, p-1);
 365   incr_top(L);
 366   func = restorestack(L, funcr);  /* previous call may change stack */
 367   setobj2s(L, func, tm);  /* tag method is the new function to be called */
 368   return func;
 369 }
 370
 371
 372
 373 #define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))
 374
 375
 376 /*
 377 ** returns true if function has been executed (C function)
 378 */
 379 int luaD_precall (lua_State *L, StkId func, int nresults) {
 380   lua_CFunction f;
 381   CallInfo *ci;
 382   int n;  /* number of arguments (Lua) or returns (C) */
 383   ptrdiff_t funcr = savestack(L, func);
 384   switch (ttype(func)) {
 385     case LUA_TLCF:  /* light C function */
 386       f = fvalue(func);
 387       goto Cfunc;
 388     case LUA_TCCL: {  /* C closure */
 389       f = clCvalue(func)->f;
 390      Cfunc:
 391       luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 392       ci = next_ci(L);  /* now 'enter' new function */
 393       ci->nresults = nresults;
 394       ci->func = restorestack(L, funcr);
 395       ci->top = L->top + LUA_MINSTACK;
 396       lua_assert(ci->top <= L->stack_last);
 397       ci->callstatus = 0;
 398       luaC_checkGC(L);  /* stack grow uses memory */
 399       if (L->hookmask & LUA_MASKCALL)
 400         luaD_hook(L, LUA_HOOKCALL, -1);
 401       lua_unlock(L);
 402       n = (*f)(L);  /* do the actual call */
 403       lua_lock(L);
 404       api_checknelems(L, n);
 405       luaD_poscall(L, L->top - n);
 406       return 1;
 407     }
 408     case LUA_TLCL: {  /* Lua function: prepare its call */
 409       StkId base;
 410       Proto *p = clLvalue(func)->p;
 411       n = cast_int(L->top - func) - 1;  /* number of real arguments */
 412       luaD_checkstack(L, p->maxstacksize + p->numparams);
 413       for (; n < p->numparams; n++)
 414         setnilvalue(L->top++);  /* complete missing arguments */
 415       if (!p->is_vararg) {
 416         func = restorestack(L, funcr);
 417         base = func + 1;
 418       }
 419       else {
 420         base = adjust_varargs(L, p, n);
 421         func = restorestack(L, funcr);  /* previous call can change stack */
 422       }
 423       ci = next_ci(L);  /* now 'enter' new function */
 424       ci->nresults = nresults;
 425       ci->func = func;
 426       ci->u.l.base = base;
 427       ci->top = base + p->maxstacksize;
 428       lua_assert(ci->top <= L->stack_last);
 429       ci->u.l.savedpc = p->code;  /* starting point */
 430       ci->callstatus = CIST_LUA;
 431       L->top = ci->top;
 432       luaC_checkGC(L);  /* stack grow uses memory */
 433       if (L->hookmask & LUA_MASKCALL)
 434         callhook(L, ci);
 435       return 0;
 436     }
 437     default: {  /* not a function */
 438       func = tryfuncTM(L, func);  /* retry with 'function' tag method */
 439       return luaD_precall(L, func, nresults);  /* now it must be a function */
 440     }
 441   }
 442 }
 443
 444
 445 int luaD_poscall (lua_State *L, StkId firstResult) {
 446   StkId res;
 447   int wanted, i;
 448   CallInfo *ci = L->ci;
 449   if (L->hookmask & (LUA_MASKRET | LUA_MASKLINE)) {
 450     if (L->hookmask & LUA_MASKRET) {
 451       ptrdiff_t fr = savestack(L, firstResult);  /* hook may change stack */
 452       luaD_hook(L, LUA_HOOKRET, -1);
 453       firstResult = restorestack(L, fr);
 454     }
 455     L->oldpc = ci->previous->u.l.savedpc;  /* 'oldpc' for caller function */
 456   }
 457   res = ci->func;  /* res == final position of 1st result */
 458   wanted = ci->nresults;
 459   L->ci = ci->previous;  /* back to caller */
 460   /* move results to correct place */
 461   for (i = wanted; i != 0 && firstResult < L->top; i--)
 462     setobjs2s(L, res++, firstResult++);
 463   while (i-- > 0)
 464     setnilvalue(res++);
 465   L->top = res;
 466   return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
 467 }
 468
 469
 470 /*
 471 ** Call a function (C or Lua). The function to be called is at *func.
 472 ** The arguments are on the stack, right after the function.
 473 ** When returns, all the results are on the stack, starting at the original
 474 ** function position.
 475 */
 476 void luaD_call (lua_State *L, StkId func, int nResults, int allowyield) {
 477   if (++L->nCcalls >= LUAI_MAXCCALLS) {
 478     if (L->nCcalls == LUAI_MAXCCALLS)
 479       luaG_runerror(L, "C stack overflow");
 480     else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
 481       luaD_throw(L, LUA_ERRERR);  /* error while handling stack error */
 482   }
 483   intptr_t remaining = stack_remaining();
 484   if (L->runerror == 0 && remaining < LUAI_MINCSTACK)
 485     luaG_runerror(L, "C stack overflow");
 486   if (L->runerror != 0 && remaining < LUAI_MINCSTACK / 2)
 487     luaD_throw(L, LUA_ERRERR);  /* error while handling stack error */
 488   if (!allowyield) L->nny++;
 489   if (!luaD_precall(L, func, nResults))  /* is a Lua function? */
 490     luaV_execute(L);  /* call it */
 491   if (!allowyield) L->nny--;
 492   L->nCcalls--;
 493 }
 494
 495
 496 static void finishCcall (lua_State *L) {
 497   CallInfo *ci = L->ci;
 498   int n;
 499   lua_assert(ci->u.c.k != NULL);  /* must have a continuation */
 500   lua_assert(L->nny == 0);
 501   if (ci->callstatus & CIST_YPCALL) {  /* was inside a pcall? */
 502     ci->callstatus &= ~CIST_YPCALL;  /* finish 'lua_pcall' */
 503     L->errfunc = ci->u.c.old_errfunc;
 504   }
 505   /* finish 'lua_callk'/'lua_pcall' */
 506   adjustresults(L, ci->nresults);
 507   /* call continuation function */
 508   if (!(ci->callstatus & CIST_STAT))  /* no call status? */
 509     ci->u.c.status = LUA_YIELD;  /* 'default' status */
 510   lua_assert(ci->u.c.status != LUA_OK);
 511   ci->callstatus = (ci->callstatus & ~(CIST_YPCALL | CIST_STAT)) | CIST_YIELDED;
 512   lua_unlock(L);
 513   n = (*ci->u.c.k)(L);
 514   lua_lock(L);
 515   api_checknelems(L, n);
 516   /* finish 'luaD_precall' */
 517   luaD_poscall(L, L->top - n);
 518 }
 519
 520
 521 static void unroll (lua_State *L, void *ud) {
 522   UNUSED(ud);
 523   for (;;) {
 524     if (L->ci == &L->base_ci)  /* stack is empty? */
 525       return;  /* coroutine finished normally */
 526     if (!isLua(L->ci))  /* C function? */
 527       finishCcall(L);
 528     else {  /* Lua function */
 529       luaV_finishOp(L);  /* finish interrupted instruction */
 530       luaV_execute(L);  /* execute down to higher C 'boundary' */
 531     }
 532   }
 533 }
 534
 535
 536 /*
 537 ** check whether thread has a suspended protected call
 538 */
 539 static CallInfo *findpcall (lua_State *L) {
 540   CallInfo *ci;
 541   for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
 542     if (ci->callstatus & CIST_YPCALL)
 543       return ci;
 544   }
 545   return NULL;  /* no pending pcall */
 546 }
 547
 548
 549 static int recover (lua_State *L, int status) {
 550   StkId oldtop;
 551   CallInfo *ci = findpcall(L);
 552   if (ci == NULL) return 0;  /* no recovery point */
 553   /* "finish" luaD_pcall */
 554   oldtop = restorestack(L, ci->extra);
 555   luaF_close(L, oldtop);
 556   seterrorobj(L, status, oldtop);
 557   L->ci = ci;
 558   L->allowhook = ci->u.c.old_allowhook;
 559   L->nny = 0;  /* should be zero to be yieldable */
 560   luaD_shrinkstack(L);
 561   L->errfunc = ci->u.c.old_errfunc;
 562   ci->callstatus |= CIST_STAT;  /* call has error status */
 563   ci->u.c.status = status;  /* (here it is) */
 564   return 1;  /* continue running the coroutine */
 565 }
 566
 567
 568 /*
 569 ** signal an error in the call to 'resume', not in the execution of the
 570 ** coroutine itself. (Such errors should not be handled by any coroutine
 571 ** error handler and should not kill the coroutine.)
 572 */
 573 static l_noret resume_error (lua_State *L, const char *msg, StkId firstArg) {
 574   L->top = firstArg;  /* remove args from the stack */
 575   setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
 576   api_incr_top(L);
 577   luaD_throw(L, -1);  /* jump back to 'lua_resume' */
 578 }
 579
 580
 581 /*
 582 ** do the work for 'lua_resume' in protected mode
 583 */
 584 static void resume_cb (lua_State *L, void *ud) {
 585   int nCcalls = L->nCcalls;
 586   StkId firstArg = cast(StkId, ud);
 587   CallInfo *ci = L->ci;
 588   if (nCcalls >= LUAI_MAXCCALLS)
 589     resume_error(L, "C stack overflow", firstArg);
 590   if (L->status == LUA_OK) {  /* may be starting a coroutine */
 591     if (ci != &L->base_ci)  /* not in base level? */
 592       resume_error(L, "cannot resume non-suspended coroutine", firstArg);
 593     /* coroutine is in base level; start running it */
 594     if (!luaD_precall(L, firstArg - 1, LUA_MULTRET))  /* Lua function? */
 595       luaV_execute(L);  /* call it */
 596   }
 597   else if (L->status != LUA_YIELD)
 598     resume_error(L, "cannot resume dead coroutine", firstArg);
 599   else {  /* resuming from previous yield */
 600     L->status = LUA_OK;
 601     ci->func = restorestack(L, ci->extra);
 602     if (isLua(ci))  /* yielded inside a hook? */
 603       luaV_execute(L);  /* just continue running Lua code */
 604     else {  /* 'common' yield */
 605       if (ci->u.c.k != NULL) {  /* does it have a continuation? */
 606         int n;
 607         ci->u.c.status = LUA_YIELD;  /* 'default' status */
 608         ci->callstatus |= CIST_YIELDED;
 609         lua_unlock(L);
 610         n = (*ci->u.c.k)(L);  /* call continuation */
 611         lua_lock(L);
 612         api_checknelems(L, n);
 613         firstArg = L->top - n;  /* yield results come from continuation */
 614       }
 615       luaD_poscall(L, firstArg);  /* finish 'luaD_precall' */
 616     }
 617     unroll(L, NULL);
 618   }
 619   lua_assert(nCcalls == L->nCcalls);
 620 }
 621
 622
 623 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
 624   int status;
 625   int oldnny = L->nny;  /* save 'nny' */
 626   lua_lock(L);
 627   luai_userstateresume(L, nargs);
 628   L->nCcalls = (from) ? from->nCcalls + 1 : 1;
 629   L->nny = 0;  /* allow yields */
 630   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
 631   status = luaD_rawrunprotected(L, resume_cb, L->top - nargs);
 632   if (status == -1)  /* error calling 'lua_resume'? */
 633     status = LUA_ERRRUN;
 634   else {  /* yield or regular error */
 635     while (status != LUA_OK && status != LUA_YIELD) {  /* error? */
 636       if (recover(L, status))  /* recover point? */
 637         status = luaD_rawrunprotected(L, unroll, NULL);  /* run continuation */
 638       else {  /* unrecoverable error */
 639         L->status = cast_byte(status);  /* mark thread as `dead' */
 640         seterrorobj(L, status, L->top);
 641         L->ci->top = L->top;
 642         break;
 643       }
 644     }
 645     lua_assert(status == L->status);
 646   }
 647   L->nny = oldnny;  /* restore 'nny' */
 648   L->nCcalls--;
 649   lua_assert(L->nCcalls == ((from) ? from->nCcalls : 0));
 650   lua_unlock(L);
 651   return status;
 652 }
 653
 654
 655 LUA_API int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k) {
 656   CallInfo *ci = L->ci;
 657   luai_userstateyield(L, nresults);
 658   lua_lock(L);
 659   api_checknelems(L, nresults);
 660   if (L->nny > 0) {
 661     if (L != G(L)->mainthread)
 662       luaG_runerror(L, "attempt to yield across a C-call boundary");
 663     else
 664       luaG_runerror(L, "attempt to yield from outside a coroutine");
 665   }
 666   L->status = LUA_YIELD;
 667   ci->extra = savestack(L, ci->func);  /* save current 'func' */
 668   if (isLua(ci)) {  /* inside a hook? */
 669     api_check(L, k == NULL, "hooks cannot continue after yielding");
 670   }
 671   else {
 672     if ((ci->u.c.k = k) != NULL)  /* is there a continuation? */
 673       ci->u.c.ctx = ctx;  /* save context */
 674     ci->func = L->top - nresults - 1;  /* protect stack below results */
 675     luaD_throw(L, LUA_YIELD);
 676   }
 677   lua_assert(ci->callstatus & CIST_HOOKED);  /* must be inside a hook */
 678   lua_unlock(L);
 679   return 0;  /* return to 'luaD_hook' */
 680 }
 681
 682
 683 int luaD_pcall (lua_State *L, Pfunc func, void *u,
 684                 ptrdiff_t old_top, ptrdiff_t ef) {
 685   int status;
 686   CallInfo *old_ci = L->ci;
 687   lu_byte old_allowhooks = L->allowhook;
 688   unsigned short old_nny = L->nny;
 689   ptrdiff_t old_errfunc = L->errfunc;
 690   L->errfunc = ef;
 691   status = luaD_rawrunprotected(L, func, u);
 692   if (status != LUA_OK) {  /* an error occurred? */
 693     StkId oldtop = restorestack(L, old_top);
 694     luaF_close(L, oldtop);  /* close possible pending closures */
 695     seterrorobj(L, status, oldtop);
 696     L->ci = old_ci;
 697     L->allowhook = old_allowhooks;
 698     L->nny = old_nny;
 699     luaD_shrinkstack(L);
 700   }
 701   L->errfunc = old_errfunc;
 702   return status;
 703 }
 704
 705
 706
 707 /*
 708 ** Execute a protected parser.
 709 */
 710 struct SParser {  /* data to `f_parser' */
 711   ZIO *z;
 712   Mbuffer buff;  /* dynamic structure used by the scanner */
 713   Dyndata dyd;  /* dynamic structures used by the parser */
 714   const char *mode;
 715   const char *name;
 716 };
 717
 718
 719 static void checkmode (lua_State *L, const char *mode, const char *x) {
 720   if (mode && strchr(mode, x[0]) == NULL) {
 721     luaO_pushfstring(L,
 722        "attempt to load a %s chunk (mode is " LUA_QS ")", x, mode);
 723     luaD_throw(L, LUA_ERRSYNTAX);
 724   }
 725 }
 726
 727
 728 static void f_parser (lua_State *L, void *ud) {
 729   int i;
 730   Closure *cl;
 731   struct SParser *p = cast(struct SParser *, ud);
 732   int c = zgetc(p->z);  /* read first character */
 733   lua_assert(c != LUA_SIGNATURE[0]);    /* binary not supported */
 734   checkmode(L, p->mode, "text");
 735   cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
 736   lua_assert(cl->l.nupvalues == cl->l.p->sizeupvalues);
 737   for (i = 0; i < cl->l.nupvalues; i++) {  /* initialize upvalues */
 738     UpVal *up = luaF_newupval(L);
 739     cl->l.upvals[i] = up;
 740     luaC_objbarrier(L, cl, up);
 741   }
 742 }
 743
 744
 745 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 746                                         const char *mode) {
 747   struct SParser p;
 748   int status;
 749   L->nny++;  /* cannot yield during parsing */
 750   p.z = z; p.name = name; p.mode = mode;
 751   p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
 752   p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
 753   p.dyd.label.arr = NULL; p.dyd.label.size = 0;
 754   luaZ_initbuffer(L, &p.buff);
 755   status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
 756   luaZ_freebuffer(L, &p.buff);
 757   luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
 758   luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
 759   luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
 760   L->nny--;
 761   return status;
 762 }