The Battle for Wesnoth  1.15.12+dev
ldo.cpp
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1 /*
2 ** $Id: ldo.c $
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 {
87  volatile int status; /* error code */
88 };
89 
90 
91 void luaD_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  case CLOSEPROTECT: {
102  setnilvalue(s2v(oldtop)); /* no error message */
103  break;
104  }
105  default: {
106  setobjs2s(L, oldtop, L->top - 1); /* error message on current top */
107  break;
108  }
109  }
110  L->top = oldtop + 1;
111 }
112 
113 
114 l_noret luaD_throw (lua_State *L, int errcode) {
115  if (L->errorJmp) { /* thread has an error handler? */
116  L->errorJmp->status = errcode; /* set status */
117  LUAI_THROW(L, L->errorJmp); /* jump to it */
118  }
119  else { /* thread has no error handler */
120  global_State *g = G(L);
121  errcode = luaF_close(L, L->stack, errcode); /* close all upvalues */
122  L->status = cast_byte(errcode); /* mark it as dead */
123  if (g->mainthread->errorJmp) { /* main thread has a handler? */
124  setobjs2s(L, g->mainthread->top++, L->top - 1); /* copy error obj. */
125  luaD_throw(g->mainthread, errcode); /* re-throw in main thread */
126  }
127  else { /* no handler at all; abort */
128  if (g->panic) { /* panic function? */
129  luaD_seterrorobj(L, errcode, L->top); /* assume EXTRA_STACK */
130  if (L->ci->top < L->top)
131  L->ci->top = L->top; /* pushing msg. can break this invariant */
132  lua_unlock(L);
133  g->panic(L); /* call panic function (last chance to jump out) */
134  }
135  abort();
136  }
137  }
138 }
139 
140 
141 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
142  l_uint32 oldnCcalls = L->nCcalls;
143  struct lua_longjmp lj;
144  lj.status = LUA_OK;
145  lj.previous = L->errorJmp; /* chain new error handler */
146  L->errorJmp = &lj;
147  LUAI_TRY(L, &lj,
148  (*f)(L, ud);
149  );
150  L->errorJmp = lj.previous; /* restore old error handler */
151  L->nCcalls = oldnCcalls;
152  return lj.status;
153 }
154 
155 /* }====================================================== */
156 
157 
158 /*
159 ** {==================================================================
160 ** Stack reallocation
161 ** ===================================================================
162 */
163 static void correctstack (lua_State *L, StkId oldstack, StkId newstack) {
164  CallInfo *ci;
165  UpVal *up;
166  if (oldstack == newstack)
167  return; /* stack address did not change */
168  L->top = (L->top - oldstack) + newstack;
169  for (up = L->openupval; up != NULL; up = up->u.open.next)
170  up->v = s2v((uplevel(up) - oldstack) + newstack);
171  for (ci = L->ci; ci != NULL; ci = ci->previous) {
172  ci->top = (ci->top - oldstack) + newstack;
173  ci->func = (ci->func - oldstack) + newstack;
174  if (isLua(ci))
175  ci->u.l.trap = 1; /* signal to update 'trap' in 'luaV_execute' */
176  }
177 }
178 
179 
180 /* some space for error handling */
181 #define ERRORSTACKSIZE (LUAI_MAXSTACK + 200)
182 
183 
184 int luaD_reallocstack (lua_State *L, int newsize, int raiseerror) {
185  int lim = stacksize(L);
186  StkId newstack = luaM_reallocvector(L, L->stack,
187  lim + EXTRA_STACK, newsize + EXTRA_STACK, StackValue);
188  lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
189  if (unlikely(newstack == NULL)) { /* reallocation failed? */
190  if (raiseerror)
191  luaM_error(L);
192  else return 0; /* do not raise an error */
193  }
194  for (; lim < newsize; lim++)
195  setnilvalue(s2v(newstack + lim + EXTRA_STACK)); /* erase new segment */
196  correctstack(L, L->stack, newstack);
197  L->stack = newstack;
198  L->stack_last = L->stack + newsize;
199  return 1;
200 }
201 
202 
203 /*
204 ** Try to grow the stack by at least 'n' elements. when 'raiseerror'
205 ** is true, raises any error; otherwise, return 0 in case of errors.
206 */
207 int luaD_growstack (lua_State *L, int n, int raiseerror) {
208  int size = stacksize(L);
209  if (unlikely(size > LUAI_MAXSTACK)) {
210  /* if stack is larger than maximum, thread is already using the
211  extra space reserved for errors, that is, thread is handling
212  a stack error; cannot grow further than that. */
214  if (raiseerror)
215  luaD_throw(L, LUA_ERRERR); /* error inside message handler */
216  return 0; /* if not 'raiseerror', just signal it */
217  }
218  else {
219  int newsize = 2 * size; /* tentative new size */
220  int needed = cast_int(L->top - L->stack) + n;
221  if (newsize > LUAI_MAXSTACK) /* cannot cross the limit */
222  newsize = LUAI_MAXSTACK;
223  if (newsize < needed) /* but must respect what was asked for */
224  newsize = needed;
225  if (likely(newsize <= LUAI_MAXSTACK))
226  return luaD_reallocstack(L, newsize, raiseerror);
227  else { /* stack overflow */
228  /* add extra size to be able to handle the error message */
229  luaD_reallocstack(L, ERRORSTACKSIZE, raiseerror);
230  if (raiseerror)
231  luaG_runerror(L, "stack overflow");
232  return 0;
233  }
234  }
235 }
236 
237 
238 static int stackinuse (lua_State *L) {
239  CallInfo *ci;
240  int res;
241  StkId lim = L->top;
242  for (ci = L->ci; ci != NULL; ci = ci->previous) {
243  if (lim < ci->top) lim = ci->top;
244  }
245  lua_assert(lim <= L->stack_last);
246  res = cast_int(lim - L->stack) + 1; /* part of stack in use */
247  if (res < LUA_MINSTACK)
248  res = LUA_MINSTACK; /* ensure a minimum size */
249  return res;
250 }
251 
252 
253 /*
254 ** If stack size is more than 3 times the current use, reduce that size
255 ** to twice the current use. (So, the final stack size is at most 2/3 the
256 ** previous size, and half of its entries are empty.)
257 ** As a particular case, if stack was handling a stack overflow and now
258 ** it is not, 'max' (limited by LUAI_MAXSTACK) will be smaller than
259 ** stacksize (equal to ERRORSTACKSIZE in this case), and so the stack
260 ** will be reduced to a "regular" size.
261 */
263  int inuse = stackinuse(L);
264  int nsize = inuse * 2; /* proposed new size */
265  int max = inuse * 3; /* maximum "reasonable" size */
266  if (max > LUAI_MAXSTACK) {
267  max = LUAI_MAXSTACK; /* respect stack limit */
268  if (nsize > LUAI_MAXSTACK)
269  nsize = LUAI_MAXSTACK;
270  }
271  /* if thread is currently not handling a stack overflow and its
272  size is larger than maximum "reasonable" size, shrink it */
273  if (inuse <= LUAI_MAXSTACK && stacksize(L) > max)
274  luaD_reallocstack(L, nsize, 0); /* ok if that fails */
275  else /* don't change stack */
276  condmovestack(L,{},{}); /* (change only for debugging) */
277  luaE_shrinkCI(L); /* shrink CI list */
278 }
279 
280 
282  luaD_checkstack(L, 1);
283  L->top++;
284 }
285 
286 /* }================================================================== */
287 
288 
289 /*
290 ** Call a hook for the given event. Make sure there is a hook to be
291 ** called. (Both 'L->hook' and 'L->hookmask', which trigger this
292 ** function, can be changed asynchronously by signals.)
293 */
294 void luaD_hook (lua_State *L, int event, int line,
295  int ftransfer, int ntransfer) {
296  lua_Hook hook = L->hook;
297  if (hook && L->allowhook) { /* make sure there is a hook */
298  int mask = CIST_HOOKED;
299  CallInfo *ci = L->ci;
300  ptrdiff_t top = savestack(L, L->top);
301  ptrdiff_t ci_top = savestack(L, ci->top);
302  lua_Debug ar;
303  ar.event = event;
304  ar.currentline = line;
305  ar.i_ci = ci;
306  if (ntransfer != 0) {
307  mask |= CIST_TRAN; /* 'ci' has transfer information */
308  ci->u2.transferinfo.ftransfer = ftransfer;
309  ci->u2.transferinfo.ntransfer = ntransfer;
310  }
311  luaD_checkstack(L, LUA_MINSTACK); /* ensure minimum stack size */
312  if (L->top + LUA_MINSTACK > ci->top)
313  ci->top = L->top + LUA_MINSTACK;
314  L->allowhook = 0; /* cannot call hooks inside a hook */
315  ci->callstatus |= mask;
316  lua_unlock(L);
317  (*hook)(L, &ar);
318  lua_lock(L);
319  lua_assert(!L->allowhook);
320  L->allowhook = 1;
321  ci->top = restorestack(L, ci_top);
322  L->top = restorestack(L, top);
323  ci->callstatus &= ~mask;
324  }
325 }
326 
327 
328 /*
329 ** Executes a call hook for Lua functions. This function is called
330 ** whenever 'hookmask' is not zero, so it checks whether call hooks are
331 ** active.
332 */
334  int hook = (ci->callstatus & CIST_TAIL) ? LUA_HOOKTAILCALL : LUA_HOOKCALL;
335  Proto *p;
336  if (!(L->hookmask & LUA_MASKCALL)) /* some other hook? */
337  return; /* don't call hook */
338  p = clLvalue(s2v(ci->func))->p;
339  L->top = ci->top; /* prepare top */
340  ci->u.l.savedpc++; /* hooks assume 'pc' is already incremented */
341  luaD_hook(L, hook, -1, 1, p->numparams);
342  ci->u.l.savedpc--; /* correct 'pc' */
343 }
344 
345 
346 static StkId rethook (lua_State *L, CallInfo *ci, StkId firstres, int nres) {
347  ptrdiff_t oldtop = savestack(L, L->top); /* hook may change top */
348  int delta = 0;
349  if (isLuacode(ci)) {
350  Proto *p = ci_func(ci)->p;
351  if (p->is_vararg)
352  delta = ci->u.l.nextraargs + p->numparams + 1;
353  if (L->top < ci->top)
354  L->top = ci->top; /* correct top to run hook */
355  }
356  if (L->hookmask & LUA_MASKRET) { /* is return hook on? */
357  int ftransfer;
358  ci->func += delta; /* if vararg, back to virtual 'func' */
359  ftransfer = cast(unsigned short, firstres - ci->func);
360  luaD_hook(L, LUA_HOOKRET, -1, ftransfer, nres); /* call it */
361  ci->func -= delta;
362  }
363  if (isLua(ci = ci->previous))
364  L->oldpc = pcRel(ci->u.l.savedpc, ci_func(ci)->p); /* update 'oldpc' */
365  return restorestack(L, oldtop);
366 }
367 
368 
369 /*
370 ** Check whether 'func' has a '__call' metafield. If so, put it in the
371 ** stack, below original 'func', so that 'luaD_precall' can call it. Raise
372 ** an error if there is no '__call' metafield.
373 */
374 void luaD_tryfuncTM (lua_State *L, StkId func) {
375  const TValue *tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);
376  StkId p;
377  if (unlikely(ttisnil(tm)))
378  luaG_typeerror(L, s2v(func), "call"); /* nothing to call */
379  for (p = L->top; p > func; p--) /* open space for metamethod */
380  setobjs2s(L, p, p-1);
381  L->top++; /* stack space pre-allocated by the caller */
382  setobj2s(L, func, tm); /* metamethod is the new function to be called */
383 }
384 
385 
386 /*
387 ** Given 'nres' results at 'firstResult', move 'wanted' of them to 'res'.
388 ** Handle most typical cases (zero results for commands, one result for
389 ** expressions, multiple results for tail calls/single parameters)
390 ** separated.
391 */
392 static void moveresults (lua_State *L, StkId res, int nres, int wanted) {
393  StkId firstresult;
394  int i;
395  switch (wanted) { /* handle typical cases separately */
396  case 0: /* no values needed */
397  L->top = res;
398  return;
399  case 1: /* one value needed */
400  if (nres == 0) /* no results? */
401  setnilvalue(s2v(res)); /* adjust with nil */
402  else
403  setobjs2s(L, res, L->top - nres); /* move it to proper place */
404  L->top = res + 1;
405  return;
406  case LUA_MULTRET:
407  wanted = nres; /* we want all results */
408  break;
409  default: /* multiple results (or to-be-closed variables) */
410  if (hastocloseCfunc(wanted)) { /* to-be-closed variables? */
411  ptrdiff_t savedres = savestack(L, res);
412  luaF_close(L, res, LUA_OK); /* may change the stack */
413  res = restorestack(L, savedres);
414  wanted = codeNresults(wanted); /* correct value */
415  if (wanted == LUA_MULTRET)
416  wanted = nres;
417  }
418  break;
419  }
420  firstresult = L->top - nres; /* index of first result */
421  /* move all results to correct place */
422  for (i = 0; i < nres && i < wanted; i++)
423  setobjs2s(L, res + i, firstresult + i);
424  for (; i < wanted; i++) /* complete wanted number of results */
425  setnilvalue(s2v(res + i));
426  L->top = res + wanted; /* top points after the last result */
427 }
428 
429 
430 /*
431 ** Finishes a function call: calls hook if necessary, removes CallInfo,
432 ** moves current number of results to proper place.
433 */
434 void luaD_poscall (lua_State *L, CallInfo *ci, int nres) {
435  if (L->hookmask)
436  L->top = rethook(L, ci, L->top - nres, nres);
437  L->ci = ci->previous; /* back to caller */
438  /* move results to proper place */
439  moveresults(L, ci->func, nres, ci->nresults);
440 }
441 
442 
443 
444 #define next_ci(L) (L->ci->next ? L->ci->next : luaE_extendCI(L))
445 
446 
447 /*
448 ** Prepare a function for a tail call, building its call info on top
449 ** of the current call info. 'narg1' is the number of arguments plus 1
450 ** (so that it includes the function itself).
451 */
452 void luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func, int narg1) {
453  Proto *p = clLvalue(s2v(func))->p;
454  int fsize = p->maxstacksize; /* frame size */
455  int nfixparams = p->numparams;
456  int i;
457  for (i = 0; i < narg1; i++) /* move down function and arguments */
458  setobjs2s(L, ci->func + i, func + i);
459  checkstackGC(L, fsize);
460  func = ci->func; /* moved-down function */
461  for (; narg1 <= nfixparams; narg1++)
462  setnilvalue(s2v(func + narg1)); /* complete missing arguments */
463  ci->top = func + 1 + fsize; /* top for new function */
464  lua_assert(ci->top <= L->stack_last);
465  ci->u.l.savedpc = p->code; /* starting point */
466  ci->callstatus |= CIST_TAIL;
467  L->top = func + narg1; /* set top */
468 }
469 
470 
471 /*
472 ** Prepares the call to a function (C or Lua). For C functions, also do
473 ** the call. The function to be called is at '*func'. The arguments
474 ** are on the stack, right after the function. Returns the CallInfo
475 ** to be executed, if it was a Lua function. Otherwise (a C function)
476 ** returns NULL, with all the results on the stack, starting at the
477 ** original function position.
478 */
479 CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
481  retry:
482  switch (ttypetag(s2v(func))) {
483  case LUA_VCCL: /* C closure */
484  f = clCvalue(s2v(func))->f;
485  goto Cfunc;
486  case LUA_VLCF: /* light C function */
487  f = fvalue(s2v(func));
488  Cfunc: {
489  int n; /* number of returns */
490  CallInfo *ci;
491  checkstackGCp(L, LUA_MINSTACK, func); /* ensure minimum stack size */
492  L->ci = ci = next_ci(L);
493  ci->nresults = nresults;
494  ci->callstatus = CIST_C;
495  ci->top = L->top + LUA_MINSTACK;
496  ci->func = func;
497  lua_assert(ci->top <= L->stack_last);
498  if (L->hookmask & LUA_MASKCALL) {
499  int narg = cast_int(L->top - func) - 1;
500  luaD_hook(L, LUA_HOOKCALL, -1, 1, narg);
501  }
502  lua_unlock(L);
503  n = (*f)(L); /* do the actual call */
504  lua_lock(L);
505  api_checknelems(L, n);
506  luaD_poscall(L, ci, n);
507  return NULL;
508  }
509  case LUA_VLCL: { /* Lua function */
510  CallInfo *ci;
511  Proto *p = clLvalue(s2v(func))->p;
512  int narg = cast_int(L->top - func) - 1; /* number of real arguments */
513  int nfixparams = p->numparams;
514  int fsize = p->maxstacksize; /* frame size */
515  checkstackGCp(L, fsize, func);
516  L->ci = ci = next_ci(L);
517  ci->nresults = nresults;
518  ci->u.l.savedpc = p->code; /* starting point */
519  ci->top = func + 1 + fsize;
520  ci->func = func;
521  L->ci = ci;
522  for (; narg < nfixparams; narg++)
523  setnilvalue(s2v(L->top++)); /* complete missing arguments */
524  lua_assert(ci->top <= L->stack_last);
525  return ci;
526  }
527  default: { /* not a function */
528  checkstackGCp(L, 1, func); /* space for metamethod */
529  luaD_tryfuncTM(L, func); /* try to get '__call' metamethod */
530  goto retry; /* try again with metamethod */
531  }
532  }
533 }
534 
535 
536 /*
537 ** Call a function (C or Lua) through C. 'inc' can be 1 (increment
538 ** number of recursive invocations in the C stack) or nyci (the same
539 ** plus increment number of non-yieldable calls).
540 */
541 static void ccall (lua_State *L, StkId func, int nResults, int inc) {
542  CallInfo *ci;
543  L->nCcalls += inc;
544  if (unlikely(getCcalls(L) >= LUAI_MAXCCALLS))
545  luaE_checkcstack(L);
546  if ((ci = luaD_precall(L, func, nResults)) != NULL) { /* Lua function? */
547  ci->callstatus = CIST_FRESH; /* mark that it is a "fresh" execute */
548  luaV_execute(L, ci); /* call it */
549  }
550  L->nCcalls -= inc;
551 }
552 
553 
554 /*
555 ** External interface for 'ccall'
556 */
557 void luaD_call (lua_State *L, StkId func, int nResults) {
558  ccall(L, func, nResults, 1);
559 }
560 
561 
562 /*
563 ** Similar to 'luaD_call', but does not allow yields during the call.
564 */
565 void luaD_callnoyield (lua_State *L, StkId func, int nResults) {
566  ccall(L, func, nResults, nyci);
567 }
568 
569 
570 /*
571 ** Completes the execution of an interrupted C function, calling its
572 ** continuation function.
573 */
574 static void finishCcall (lua_State *L, int status) {
575  CallInfo *ci = L->ci;
576  int n;
577  /* must have a continuation and must be able to call it */
578  lua_assert(ci->u.c.k != NULL && yieldable(L));
579  /* error status can only happen in a protected call */
580  lua_assert((ci->callstatus & CIST_YPCALL) || status == LUA_YIELD);
581  if (ci->callstatus & CIST_YPCALL) { /* was inside a pcall? */
582  ci->callstatus &= ~CIST_YPCALL; /* continuation is also inside it */
583  L->errfunc = ci->u.c.old_errfunc; /* with the same error function */
584  }
585  /* finish 'lua_callk'/'lua_pcall'; CIST_YPCALL and 'errfunc' already
586  handled */
587  adjustresults(L, ci->nresults);
588  lua_unlock(L);
589  n = (*ci->u.c.k)(L, status, ci->u.c.ctx); /* call continuation function */
590  lua_lock(L);
591  api_checknelems(L, n);
592  luaD_poscall(L, ci, n); /* finish 'luaD_call' */
593 }
594 
595 
596 /*
597 ** Executes "full continuation" (everything in the stack) of a
598 ** previously interrupted coroutine until the stack is empty (or another
599 ** interruption long-jumps out of the loop). If the coroutine is
600 ** recovering from an error, 'ud' points to the error status, which must
601 ** be passed to the first continuation function (otherwise the default
602 ** status is LUA_YIELD).
603 */
604 static void unroll (lua_State *L, void *ud) {
605  CallInfo *ci;
606  if (ud != NULL) /* error status? */
607  finishCcall(L, *(int *)ud); /* finish 'lua_pcallk' callee */
608  while ((ci = L->ci) != &L->base_ci) { /* something in the stack */
609  if (!isLua(ci)) /* C function? */
610  finishCcall(L, LUA_YIELD); /* complete its execution */
611  else { /* Lua function */
612  luaV_finishOp(L); /* finish interrupted instruction */
613  luaV_execute(L, ci); /* execute down to higher C 'boundary' */
614  }
615  }
616 }
617 
618 
619 /*
620 ** Try to find a suspended protected call (a "recover point") for the
621 ** given thread.
622 */
624  CallInfo *ci;
625  for (ci = L->ci; ci != NULL; ci = ci->previous) { /* search for a pcall */
626  if (ci->callstatus & CIST_YPCALL)
627  return ci;
628  }
629  return NULL; /* no pending pcall */
630 }
631 
632 
633 /*
634 ** Recovers from an error in a coroutine. Finds a recover point (if
635 ** there is one) and completes the execution of the interrupted
636 ** 'luaD_pcall'. If there is no recover point, returns zero.
637 */
638 static int recover (lua_State *L, int status) {
639  StkId oldtop;
640  CallInfo *ci = findpcall(L);
641  if (ci == NULL) return 0; /* no recovery point */
642  /* "finish" luaD_pcall */
643  oldtop = restorestack(L, ci->u2.funcidx);
644  L->ci = ci;
645  L->allowhook = getoah(ci->callstatus); /* restore original 'allowhook' */
646  status = luaF_close(L, oldtop, status); /* may change the stack */
647  oldtop = restorestack(L, ci->u2.funcidx);
648  luaD_seterrorobj(L, status, oldtop);
649  luaD_shrinkstack(L); /* restore stack size in case of overflow */
650  L->errfunc = ci->u.c.old_errfunc;
651  return 1; /* continue running the coroutine */
652 }
653 
654 
655 /*
656 ** Signal an error in the call to 'lua_resume', not in the execution
657 ** of the coroutine itself. (Such errors should not be handled by any
658 ** coroutine error handler and should not kill the coroutine.)
659 */
660 static int resume_error (lua_State *L, const char *msg, int narg) {
661  L->top -= narg; /* remove args from the stack */
662  setsvalue2s(L, L->top, luaS_new(L, msg)); /* push error message */
663  api_incr_top(L);
664  lua_unlock(L);
665  return LUA_ERRRUN;
666 }
667 
668 
669 /*
670 ** Do the work for 'lua_resume' in protected mode. Most of the work
671 ** depends on the status of the coroutine: initial state, suspended
672 ** inside a hook, or regularly suspended (optionally with a continuation
673 ** function), plus erroneous cases: non-suspended coroutine or dead
674 ** coroutine.
675 */
676 static void resume (lua_State *L, void *ud) {
677  int n = *(cast(int*, ud)); /* number of arguments */
678  StkId firstArg = L->top - n; /* first argument */
679  CallInfo *ci = L->ci;
680  if (L->status == LUA_OK) /* starting a coroutine? */
681  ccall(L, firstArg - 1, LUA_MULTRET, 1); /* just call its body */
682  else { /* resuming from previous yield */
683  lua_assert(L->status == LUA_YIELD);
684  L->status = LUA_OK; /* mark that it is running (again) */
685  luaE_incCstack(L); /* control the C stack */
686  if (isLua(ci)) /* yielded inside a hook? */
687  luaV_execute(L, ci); /* just continue running Lua code */
688  else { /* 'common' yield */
689  if (ci->u.c.k != NULL) { /* does it have a continuation function? */
690  lua_unlock(L);
691  n = (*ci->u.c.k)(L, LUA_YIELD, ci->u.c.ctx); /* call continuation */
692  lua_lock(L);
693  api_checknelems(L, n);
694  }
695  luaD_poscall(L, ci, n); /* finish 'luaD_call' */
696  }
697  unroll(L, NULL); /* run continuation */
698  }
699 }
700 
701 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
702  int *nresults) {
703  int status;
704  lua_lock(L);
705  if (L->status == LUA_OK) { /* may be starting a coroutine */
706  if (L->ci != &L->base_ci) /* not in base level? */
707  return resume_error(L, "cannot resume non-suspended coroutine", nargs);
708  else if (L->top - (L->ci->func + 1) == nargs) /* no function? */
709  return resume_error(L, "cannot resume dead coroutine", nargs);
710  }
711  else if (L->status != LUA_YIELD) /* ended with errors? */
712  return resume_error(L, "cannot resume dead coroutine", nargs);
713  L->nCcalls = (from) ? getCcalls(from) : 0;
714  luai_userstateresume(L, nargs);
715  api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
716  status = luaD_rawrunprotected(L, resume, &nargs);
717  /* continue running after recoverable errors */
718  while (errorstatus(status) && recover(L, status)) {
719  /* unroll continuation */
720  status = luaD_rawrunprotected(L, unroll, &status);
721  }
722  if (likely(!errorstatus(status)))
723  lua_assert(status == L->status); /* normal end or yield */
724  else { /* unrecoverable error */
725  L->status = cast_byte(status); /* mark thread as 'dead' */
726  luaD_seterrorobj(L, status, L->top); /* push error message */
727  L->ci->top = L->top;
728  }
729  *nresults = (status == LUA_YIELD) ? L->ci->u2.nyield
730  : cast_int(L->top - (L->ci->func + 1));
731  lua_unlock(L);
732  return status;
733 }
734 
735 
737  return yieldable(L);
738 }
739 
740 
741 LUA_API int lua_yieldk (lua_State *L, int nresults, lua_KContext ctx,
742  lua_KFunction k) {
743  CallInfo *ci;
744  luai_userstateyield(L, nresults);
745  lua_lock(L);
746  ci = L->ci;
747  api_checknelems(L, nresults);
748  if (unlikely(!yieldable(L))) {
749  if (L != G(L)->mainthread)
750  luaG_runerror(L, "attempt to yield across a C-call boundary");
751  else
752  luaG_runerror(L, "attempt to yield from outside a coroutine");
753  }
754  L->status = LUA_YIELD;
755  if (isLua(ci)) { /* inside a hook? */
756  lua_assert(!isLuacode(ci));
757  api_check(L, k == NULL, "hooks cannot continue after yielding");
758  ci->u2.nyield = 0; /* no results */
759  }
760  else {
761  if ((ci->u.c.k = k) != NULL) /* is there a continuation? */
762  ci->u.c.ctx = ctx; /* save context */
763  ci->u2.nyield = nresults; /* save number of results */
764  luaD_throw(L, LUA_YIELD);
765  }
766  lua_assert(ci->callstatus & CIST_HOOKED); /* must be inside a hook */
767  lua_unlock(L);
768  return 0; /* return to 'luaD_hook' */
769 }
770 
771 
772 /*
773 ** Call the C function 'func' in protected mode, restoring basic
774 ** thread information ('allowhook', etc.) and in particular
775 ** its stack level in case of errors.
776 */
777 int luaD_pcall (lua_State *L, Pfunc func, void *u,
778  ptrdiff_t old_top, ptrdiff_t ef) {
779  int status;
780  CallInfo *old_ci = L->ci;
781  lu_byte old_allowhooks = L->allowhook;
782  ptrdiff_t old_errfunc = L->errfunc;
783  L->errfunc = ef;
784  status = luaD_rawrunprotected(L, func, u);
785  if (unlikely(status != LUA_OK)) { /* an error occurred? */
786  StkId oldtop = restorestack(L, old_top);
787  L->ci = old_ci;
788  L->allowhook = old_allowhooks;
789  status = luaF_close(L, oldtop, status);
790  oldtop = restorestack(L, old_top); /* previous call may change stack */
791  luaD_seterrorobj(L, status, oldtop);
792  luaD_shrinkstack(L); /* restore stack size in case of overflow */
793  }
794  L->errfunc = old_errfunc;
795  return status;
796 }
797 
798 
799 
800 /*
801 ** Execute a protected parser.
802 */
803 struct SParser { /* data to 'f_parser' */
804  ZIO *z;
805  Mbuffer buff; /* dynamic structure used by the scanner */
806  Dyndata dyd; /* dynamic structures used by the parser */
807  const char *mode;
808  const char *name;
809 };
810 
811 
812 static void checkmode (lua_State *L, const char *mode, const char *x) {
813  if (mode && strchr(mode, x[0]) == NULL) {
815  "attempt to load a %s chunk (mode is '%s')", x, mode);
817  }
818 }
819 
820 
821 static void f_parser (lua_State *L, void *ud) {
822  LClosure *cl;
823  struct SParser *p = cast(struct SParser *, ud);
824  int c = zgetc(p->z); /* read first character */
825  if (c == LUA_SIGNATURE[0]) {
826  checkmode(L, p->mode, "binary");
827  cl = luaU_undump(L, p->z, p->name);
828  }
829  else {
830  checkmode(L, p->mode, "text");
831  cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
832  }
833  lua_assert(cl->nupvalues == cl->p->sizeupvalues);
834  luaF_initupvals(L, cl);
835 }
836 
837 
838 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
839  const char *mode) {
840  struct SParser p;
841  int status;
842  incnny(L); /* cannot yield during parsing */
843  p.z = z; p.name = name; p.mode = mode;
844  p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
845  p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
846  p.dyd.label.arr = NULL; p.dyd.label.size = 0;
847  luaZ_initbuffer(L, &p.buff);
848  status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
849  luaZ_freebuffer(L, &p.buff);
851  luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
853  decnny(L);
854  return status;
855 }
856 
857 
#define LUA_HOOKCALL
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