xref: /freebsd/contrib/lua/src/ldo.c (revision 64c2a712d661db9be31f02fe97c3b59710290ae3)
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 {
85    struct lua_longjmp *previous;
86    luai_jmpbuf b;
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 LUA_OK: {  /* special case only for closing upvalues */
102        setnilvalue(s2v(oldtop));  /* no error message */
103        break;
104      }
105      default: {
106        lua_assert(errorstatus(errcode));  /* real error */
107        setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
108        break;
109      }
110    }
111    L->top = oldtop + 1;
112  }
113  
114  
115  l_noret luaD_throw (lua_State *L, int errcode) {
116    if (L->errorJmp) {  /* thread has an error handler? */
117      L->errorJmp->status = errcode;  /* set status */
118      LUAI_THROW(L, L->errorJmp);  /* jump to it */
119    }
120    else {  /* thread has no error handler */
121      global_State *g = G(L);
122      errcode = luaE_resetthread(L, errcode);  /* close all upvalues */
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          lua_unlock(L);
130          g->panic(L);  /* call panic function (last chance to jump out) */
131        }
132        abort();
133      }
134    }
135  }
136  
137  
138  int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
139    l_uint32 oldnCcalls = L->nCcalls;
140    struct lua_longjmp lj;
141    lj.status = LUA_OK;
142    lj.previous = L->errorJmp;  /* chain new error handler */
143    L->errorJmp = &lj;
144    LUAI_TRY(L, &lj,
145      (*f)(L, ud);
146    );
147    L->errorJmp = lj.previous;  /* restore old error handler */
148    L->nCcalls = oldnCcalls;
149    return lj.status;
150  }
151  
152  /* }====================================================== */
153  
154  
155  /*
156  ** {==================================================================
157  ** Stack reallocation
158  ** ===================================================================
159  */
160  static void correctstack (lua_State *L, StkId oldstack, StkId newstack) {
161    CallInfo *ci;
162    UpVal *up;
163    L->top = (L->top - oldstack) + newstack;
164    L->tbclist = (L->tbclist - oldstack) + newstack;
165    for (up = L->openupval; up != NULL; up = up->u.open.next)
166      up->v = s2v((uplevel(up) - oldstack) + newstack);
167    for (ci = L->ci; ci != NULL; ci = ci->previous) {
168      ci->top = (ci->top - oldstack) + newstack;
169      ci->func = (ci->func - oldstack) + newstack;
170      if (isLua(ci))
171        ci->u.l.trap = 1;  /* signal to update 'trap' in 'luaV_execute' */
172    }
173  }
174  
175  
176  /* some space for error handling */
177  #define ERRORSTACKSIZE	(LUAI_MAXSTACK + 200)
178  
179  
180  /*
181  ** Reallocate the stack to a new size, correcting all pointers into
182  ** it. (There are pointers to a stack from its upvalues, from its list
183  ** of call infos, plus a few individual pointers.) The reallocation is
184  ** done in two steps (allocation + free) because the correction must be
185  ** done while both addresses (the old stack and the new one) are valid.
186  ** (In ISO C, any pointer use after the pointer has been deallocated is
187  ** undefined behavior.)
188  ** In case of allocation error, raise an error or return false according
189  ** to 'raiseerror'.
190  */
191  int luaD_reallocstack (lua_State *L, int newsize, int raiseerror) {
192    int oldsize = stacksize(L);
193    int i;
194    StkId newstack = luaM_reallocvector(L, NULL, 0,
195                                        newsize + EXTRA_STACK, StackValue);
196    lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
197    if (l_unlikely(newstack == NULL)) {  /* reallocation failed? */
198      if (raiseerror)
199        luaM_error(L);
200      else return 0;  /* do not raise an error */
201    }
202    /* number of elements to be copied to the new stack */
203    i = ((oldsize <= newsize) ? oldsize : newsize) + EXTRA_STACK;
204    memcpy(newstack, L->stack, i * sizeof(StackValue));
205    for (; i < newsize + EXTRA_STACK; i++)
206      setnilvalue(s2v(newstack + i)); /* erase new segment */
207    correctstack(L, L->stack, newstack);
208    luaM_freearray(L, L->stack, oldsize + EXTRA_STACK);
209    L->stack = newstack;
210    L->stack_last = L->stack + newsize;
211    return 1;
212  }
213  
214  
215  /*
216  ** Try to grow the stack by at least 'n' elements. when 'raiseerror'
217  ** is true, raises any error; otherwise, return 0 in case of errors.
218  */
219  int luaD_growstack (lua_State *L, int n, int raiseerror) {
220    int size = stacksize(L);
221    if (l_unlikely(size > LUAI_MAXSTACK)) {
222      /* if stack is larger than maximum, thread is already using the
223         extra space reserved for errors, that is, thread is handling
224         a stack error; cannot grow further than that. */
225      lua_assert(stacksize(L) == ERRORSTACKSIZE);
226      if (raiseerror)
227        luaD_throw(L, LUA_ERRERR);  /* error inside message handler */
228      return 0;  /* if not 'raiseerror', just signal it */
229    }
230    else {
231      int newsize = 2 * size;  /* tentative new size */
232      int needed = cast_int(L->top - L->stack) + n;
233      if (newsize > LUAI_MAXSTACK)  /* cannot cross the limit */
234        newsize = LUAI_MAXSTACK;
235      if (newsize < needed)  /* but must respect what was asked for */
236        newsize = needed;
237      if (l_likely(newsize <= LUAI_MAXSTACK))
238        return luaD_reallocstack(L, newsize, raiseerror);
239      else {  /* stack overflow */
240        /* add extra size to be able to handle the error message */
241        luaD_reallocstack(L, ERRORSTACKSIZE, raiseerror);
242        if (raiseerror)
243          luaG_runerror(L, "stack overflow");
244        return 0;
245      }
246    }
247  }
248  
249  
250  static int stackinuse (lua_State *L) {
251    CallInfo *ci;
252    int res;
253    StkId lim = L->top;
254    for (ci = L->ci; ci != NULL; ci = ci->previous) {
255      if (lim < ci->top) lim = ci->top;
256    }
257    lua_assert(lim <= L->stack_last);
258    res = cast_int(lim - L->stack) + 1;  /* part of stack in use */
259    if (res < LUA_MINSTACK)
260      res = LUA_MINSTACK;  /* ensure a minimum size */
261    return res;
262  }
263  
264  
265  /*
266  ** If stack size is more than 3 times the current use, reduce that size
267  ** to twice the current use. (So, the final stack size is at most 2/3 the
268  ** previous size, and half of its entries are empty.)
269  ** As a particular case, if stack was handling a stack overflow and now
270  ** it is not, 'max' (limited by LUAI_MAXSTACK) will be smaller than
271  ** stacksize (equal to ERRORSTACKSIZE in this case), and so the stack
272  ** will be reduced to a "regular" size.
273  */
274  void luaD_shrinkstack (lua_State *L) {
275    int inuse = stackinuse(L);
276    int nsize = inuse * 2;  /* proposed new size */
277    int max = inuse * 3;  /* maximum "reasonable" size */
278    if (max > LUAI_MAXSTACK) {
279      max = LUAI_MAXSTACK;  /* respect stack limit */
280      if (nsize > LUAI_MAXSTACK)
281        nsize = LUAI_MAXSTACK;
282    }
283    /* if thread is currently not handling a stack overflow and its
284       size is larger than maximum "reasonable" size, shrink it */
285    if (inuse <= LUAI_MAXSTACK && stacksize(L) > max)
286      luaD_reallocstack(L, nsize, 0);  /* ok if that fails */
287    else  /* don't change stack */
288      condmovestack(L,{},{});  /* (change only for debugging) */
289    luaE_shrinkCI(L);  /* shrink CI list */
290  }
291  
292  
293  void luaD_inctop (lua_State *L) {
294    luaD_checkstack(L, 1);
295    L->top++;
296  }
297  
298  /* }================================================================== */
299  
300  
301  /*
302  ** Call a hook for the given event. Make sure there is a hook to be
303  ** called. (Both 'L->hook' and 'L->hookmask', which trigger this
304  ** function, can be changed asynchronously by signals.)
305  */
306  void luaD_hook (lua_State *L, int event, int line,
307                                int ftransfer, int ntransfer) {
308    lua_Hook hook = L->hook;
309    if (hook && L->allowhook) {  /* make sure there is a hook */
310      int mask = CIST_HOOKED;
311      CallInfo *ci = L->ci;
312      ptrdiff_t top = savestack(L, L->top);  /* preserve original 'top' */
313      ptrdiff_t ci_top = savestack(L, ci->top);  /* idem for 'ci->top' */
314      lua_Debug ar;
315      ar.event = event;
316      ar.currentline = line;
317      ar.i_ci = ci;
318      if (ntransfer != 0) {
319        mask |= CIST_TRAN;  /* 'ci' has transfer information */
320        ci->u2.transferinfo.ftransfer = ftransfer;
321        ci->u2.transferinfo.ntransfer = ntransfer;
322      }
323      if (isLua(ci) && L->top < ci->top)
324        L->top = ci->top;  /* protect entire activation register */
325      luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
326      if (ci->top < L->top + LUA_MINSTACK)
327        ci->top = L->top + LUA_MINSTACK;
328      L->allowhook = 0;  /* cannot call hooks inside a hook */
329      ci->callstatus |= mask;
330      lua_unlock(L);
331      (*hook)(L, &ar);
332      lua_lock(L);
333      lua_assert(!L->allowhook);
334      L->allowhook = 1;
335      ci->top = restorestack(L, ci_top);
336      L->top = restorestack(L, top);
337      ci->callstatus &= ~mask;
338    }
339  }
340  
341  
342  /*
343  ** Executes a call hook for Lua functions. This function is called
344  ** whenever 'hookmask' is not zero, so it checks whether call hooks are
345  ** active.
346  */
347  void luaD_hookcall (lua_State *L, CallInfo *ci) {
348    L->oldpc = 0;  /* set 'oldpc' for new function */
349    if (L->hookmask & LUA_MASKCALL) {  /* is call hook on? */
350      int event = (ci->callstatus & CIST_TAIL) ? LUA_HOOKTAILCALL
351                                               : LUA_HOOKCALL;
352      Proto *p = ci_func(ci)->p;
353      ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */
354      luaD_hook(L, event, -1, 1, p->numparams);
355      ci->u.l.savedpc--;  /* correct 'pc' */
356    }
357  }
358  
359  
360  /*
361  ** Executes a return hook for Lua and C functions and sets/corrects
362  ** 'oldpc'. (Note that this correction is needed by the line hook, so it
363  ** is done even when return hooks are off.)
364  */
365  static void rethook (lua_State *L, CallInfo *ci, int nres) {
366    if (L->hookmask & LUA_MASKRET) {  /* is return hook on? */
367      StkId firstres = L->top - nres;  /* index of first result */
368      int delta = 0;  /* correction for vararg functions */
369      int ftransfer;
370      if (isLua(ci)) {
371        Proto *p = ci_func(ci)->p;
372        if (p->is_vararg)
373          delta = ci->u.l.nextraargs + p->numparams + 1;
374      }
375      ci->func += delta;  /* if vararg, back to virtual 'func' */
376      ftransfer = cast(unsigned short, firstres - ci->func);
377      luaD_hook(L, LUA_HOOKRET, -1, ftransfer, nres);  /* call it */
378      ci->func -= delta;
379    }
380    if (isLua(ci = ci->previous))
381      L->oldpc = pcRel(ci->u.l.savedpc, ci_func(ci)->p);  /* set 'oldpc' */
382  }
383  
384  
385  /*
386  ** Check whether 'func' has a '__call' metafield. If so, put it in the
387  ** stack, below original 'func', so that 'luaD_precall' can call it. Raise
388  ** an error if there is no '__call' metafield.
389  */
390  StkId luaD_tryfuncTM (lua_State *L, StkId func) {
391    const TValue *tm;
392    StkId p;
393    checkstackGCp(L, 1, func);  /* space for metamethod */
394    tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);  /* (after previous GC) */
395    if (l_unlikely(ttisnil(tm)))
396      luaG_callerror(L, s2v(func));  /* nothing to call */
397    for (p = L->top; p > func; p--)  /* open space for metamethod */
398      setobjs2s(L, p, p-1);
399    L->top++;  /* stack space pre-allocated by the caller */
400    setobj2s(L, func, tm);  /* metamethod is the new function to be called */
401    return func;
402  }
403  
404  
405  /*
406  ** Given 'nres' results at 'firstResult', move 'wanted' of them to 'res'.
407  ** Handle most typical cases (zero results for commands, one result for
408  ** expressions, multiple results for tail calls/single parameters)
409  ** separated.
410  */
411  l_sinline void moveresults (lua_State *L, StkId res, int nres, int wanted) {
412    StkId firstresult;
413    int i;
414    switch (wanted) {  /* handle typical cases separately */
415      case 0:  /* no values needed */
416        L->top = res;
417        return;
418      case 1:  /* one value needed */
419        if (nres == 0)   /* no results? */
420          setnilvalue(s2v(res));  /* adjust with nil */
421        else  /* at least one result */
422          setobjs2s(L, res, L->top - nres);  /* move it to proper place */
423        L->top = res + 1;
424        return;
425      case LUA_MULTRET:
426        wanted = nres;  /* we want all results */
427        break;
428      default:  /* two/more results and/or to-be-closed variables */
429        if (hastocloseCfunc(wanted)) {  /* to-be-closed variables? */
430          ptrdiff_t savedres = savestack(L, res);
431          L->ci->callstatus |= CIST_CLSRET;  /* in case of yields */
432          L->ci->u2.nres = nres;
433          luaF_close(L, res, CLOSEKTOP, 1);
434          L->ci->callstatus &= ~CIST_CLSRET;
435          if (L->hookmask)  /* if needed, call hook after '__close's */
436            rethook(L, L->ci, nres);
437          res = restorestack(L, savedres);  /* close and hook can move stack */
438          wanted = decodeNresults(wanted);
439          if (wanted == LUA_MULTRET)
440            wanted = nres;  /* we want all results */
441        }
442        break;
443    }
444    /* generic case */
445    firstresult = L->top - nres;  /* index of first result */
446    if (nres > wanted)  /* extra results? */
447      nres = wanted;  /* don't need them */
448    for (i = 0; i < nres; i++)  /* move all results to correct place */
449      setobjs2s(L, res + i, firstresult + i);
450    for (; i < wanted; i++)  /* complete wanted number of results */
451      setnilvalue(s2v(res + i));
452    L->top = res + wanted;  /* top points after the last result */
453  }
454  
455  
456  /*
457  ** Finishes a function call: calls hook if necessary, moves current
458  ** number of results to proper place, and returns to previous call
459  ** info. If function has to close variables, hook must be called after
460  ** that.
461  */
462  void luaD_poscall (lua_State *L, CallInfo *ci, int nres) {
463    int wanted = ci->nresults;
464    if (l_unlikely(L->hookmask && !hastocloseCfunc(wanted)))
465      rethook(L, ci, nres);
466    /* move results to proper place */
467    moveresults(L, ci->func, nres, wanted);
468    /* function cannot be in any of these cases when returning */
469    lua_assert(!(ci->callstatus &
470          (CIST_HOOKED | CIST_YPCALL | CIST_FIN | CIST_TRAN | CIST_CLSRET)));
471    L->ci = ci->previous;  /* back to caller (after closing variables) */
472  }
473  
474  
475  
476  #define next_ci(L)  (L->ci->next ? L->ci->next : luaE_extendCI(L))
477  
478  
479  l_sinline CallInfo *prepCallInfo (lua_State *L, StkId func, int nret,
480                                                  int mask, StkId top) {
481    CallInfo *ci = L->ci = next_ci(L);  /* new frame */
482    ci->func = func;
483    ci->nresults = nret;
484    ci->callstatus = mask;
485    ci->top = top;
486    return ci;
487  }
488  
489  
490  /*
491  ** precall for C functions
492  */
493  l_sinline int precallC (lua_State *L, StkId func, int nresults,
494                                              lua_CFunction f) {
495    int n;  /* number of returns */
496    CallInfo *ci;
497    checkstackGCp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
498    L->ci = ci = prepCallInfo(L, func, nresults, CIST_C,
499                                 L->top + LUA_MINSTACK);
500    lua_assert(ci->top <= L->stack_last);
501    if (l_unlikely(L->hookmask & LUA_MASKCALL)) {
502      int narg = cast_int(L->top - func) - 1;
503      luaD_hook(L, LUA_HOOKCALL, -1, 1, narg);
504    }
505    lua_unlock(L);
506    n = (*f)(L);  /* do the actual call */
507    lua_lock(L);
508    api_checknelems(L, n);
509    luaD_poscall(L, ci, n);
510    return n;
511  }
512  
513  
514  /*
515  ** Prepare a function for a tail call, building its call info on top
516  ** of the current call info. 'narg1' is the number of arguments plus 1
517  ** (so that it includes the function itself). Return the number of
518  ** results, if it was a C function, or -1 for a Lua function.
519  */
520  int luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func,
521                                      int narg1, int delta) {
522   retry:
523    switch (ttypetag(s2v(func))) {
524      case LUA_VCCL:  /* C closure */
525        return precallC(L, func, LUA_MULTRET, clCvalue(s2v(func))->f);
526      case LUA_VLCF:  /* light C function */
527        return precallC(L, func, LUA_MULTRET, fvalue(s2v(func)));
528      case LUA_VLCL: {  /* Lua function */
529        Proto *p = clLvalue(s2v(func))->p;
530        int fsize = p->maxstacksize;  /* frame size */
531        int nfixparams = p->numparams;
532        int i;
533        checkstackGCp(L, fsize - delta, func);
534        ci->func -= delta;  /* restore 'func' (if vararg) */
535        for (i = 0; i < narg1; i++)  /* move down function and arguments */
536          setobjs2s(L, ci->func + i, func + i);
537        func = ci->func;  /* moved-down function */
538        for (; narg1 <= nfixparams; narg1++)
539          setnilvalue(s2v(func + narg1));  /* complete missing arguments */
540        ci->top = func + 1 + fsize;  /* top for new function */
541        lua_assert(ci->top <= L->stack_last);
542        ci->u.l.savedpc = p->code;  /* starting point */
543        ci->callstatus |= CIST_TAIL;
544        L->top = func + narg1;  /* set top */
545        return -1;
546      }
547      default: {  /* not a function */
548        func = luaD_tryfuncTM(L, func);  /* try to get '__call' metamethod */
549        /* return luaD_pretailcall(L, ci, func, narg1 + 1, delta); */
550        narg1++;
551        goto retry;  /* try again */
552      }
553    }
554  }
555  
556  
557  /*
558  ** Prepares the call to a function (C or Lua). For C functions, also do
559  ** the call. The function to be called is at '*func'.  The arguments
560  ** are on the stack, right after the function.  Returns the CallInfo
561  ** to be executed, if it was a Lua function. Otherwise (a C function)
562  ** returns NULL, with all the results on the stack, starting at the
563  ** original function position.
564  */
565  CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
566   retry:
567    switch (ttypetag(s2v(func))) {
568      case LUA_VCCL:  /* C closure */
569        precallC(L, func, nresults, clCvalue(s2v(func))->f);
570        return NULL;
571      case LUA_VLCF:  /* light C function */
572        precallC(L, func, nresults, fvalue(s2v(func)));
573        return NULL;
574      case LUA_VLCL: {  /* Lua function */
575        CallInfo *ci;
576        Proto *p = clLvalue(s2v(func))->p;
577        int narg = cast_int(L->top - func) - 1;  /* number of real arguments */
578        int nfixparams = p->numparams;
579        int fsize = p->maxstacksize;  /* frame size */
580        checkstackGCp(L, fsize, func);
581        L->ci = ci = prepCallInfo(L, func, nresults, 0, func + 1 + fsize);
582        ci->u.l.savedpc = p->code;  /* starting point */
583        for (; narg < nfixparams; narg++)
584          setnilvalue(s2v(L->top++));  /* complete missing arguments */
585        lua_assert(ci->top <= L->stack_last);
586        return ci;
587      }
588      default: {  /* not a function */
589        func = luaD_tryfuncTM(L, func);  /* try to get '__call' metamethod */
590        /* return luaD_precall(L, func, nresults); */
591        goto retry;  /* try again with metamethod */
592      }
593    }
594  }
595  
596  
597  /*
598  ** Call a function (C or Lua) through C. 'inc' can be 1 (increment
599  ** number of recursive invocations in the C stack) or nyci (the same
600  ** plus increment number of non-yieldable calls).
601  */
602  l_sinline void ccall (lua_State *L, StkId func, int nResults, int inc) {
603    CallInfo *ci;
604    L->nCcalls += inc;
605    if (l_unlikely(getCcalls(L) >= LUAI_MAXCCALLS))
606      luaE_checkcstack(L);
607    if ((ci = luaD_precall(L, func, nResults)) != NULL) {  /* Lua function? */
608      ci->callstatus = CIST_FRESH;  /* mark that it is a "fresh" execute */
609      luaV_execute(L, ci);  /* call it */
610    }
611    L->nCcalls -= inc;
612  }
613  
614  
615  /*
616  ** External interface for 'ccall'
617  */
618  void luaD_call (lua_State *L, StkId func, int nResults) {
619    ccall(L, func, nResults, 1);
620  }
621  
622  
623  /*
624  ** Similar to 'luaD_call', but does not allow yields during the call.
625  */
626  void luaD_callnoyield (lua_State *L, StkId func, int nResults) {
627    ccall(L, func, nResults, nyci);
628  }
629  
630  
631  /*
632  ** Finish the job of 'lua_pcallk' after it was interrupted by an yield.
633  ** (The caller, 'finishCcall', does the final call to 'adjustresults'.)
634  ** The main job is to complete the 'luaD_pcall' called by 'lua_pcallk'.
635  ** If a '__close' method yields here, eventually control will be back
636  ** to 'finishCcall' (when that '__close' method finally returns) and
637  ** 'finishpcallk' will run again and close any still pending '__close'
638  ** methods. Similarly, if a '__close' method errs, 'precover' calls
639  ** 'unroll' which calls ''finishCcall' and we are back here again, to
640  ** close any pending '__close' methods.
641  ** Note that, up to the call to 'luaF_close', the corresponding
642  ** 'CallInfo' is not modified, so that this repeated run works like the
643  ** first one (except that it has at least one less '__close' to do). In
644  ** particular, field CIST_RECST preserves the error status across these
645  ** multiple runs, changing only if there is a new error.
646  */
647  static int finishpcallk (lua_State *L,  CallInfo *ci) {
648    int status = getcistrecst(ci);  /* get original status */
649    if (l_likely(status == LUA_OK))  /* no error? */
650      status = LUA_YIELD;  /* was interrupted by an yield */
651    else {  /* error */
652      StkId func = restorestack(L, ci->u2.funcidx);
653      L->allowhook = getoah(ci->callstatus);  /* restore 'allowhook' */
654      luaF_close(L, func, status, 1);  /* can yield or raise an error */
655      func = restorestack(L, ci->u2.funcidx);  /* stack may be moved */
656      luaD_seterrorobj(L, status, func);
657      luaD_shrinkstack(L);   /* restore stack size in case of overflow */
658      setcistrecst(ci, LUA_OK);  /* clear original status */
659    }
660    ci->callstatus &= ~CIST_YPCALL;
661    L->errfunc = ci->u.c.old_errfunc;
662    /* if it is here, there were errors or yields; unlike 'lua_pcallk',
663       do not change status */
664    return status;
665  }
666  
667  
668  /*
669  ** Completes the execution of a C function interrupted by an yield.
670  ** The interruption must have happened while the function was either
671  ** closing its tbc variables in 'moveresults' or executing
672  ** 'lua_callk'/'lua_pcallk'. In the first case, it just redoes
673  ** 'luaD_poscall'. In the second case, the call to 'finishpcallk'
674  ** finishes the interrupted execution of 'lua_pcallk'.  After that, it
675  ** calls the continuation of the interrupted function and finally it
676  ** completes the job of the 'luaD_call' that called the function.  In
677  ** the call to 'adjustresults', we do not know the number of results
678  ** of the function called by 'lua_callk'/'lua_pcallk', so we are
679  ** conservative and use LUA_MULTRET (always adjust).
680  */
681  static void finishCcall (lua_State *L, CallInfo *ci) {
682    int n;  /* actual number of results from C function */
683    if (ci->callstatus & CIST_CLSRET) {  /* was returning? */
684      lua_assert(hastocloseCfunc(ci->nresults));
685      n = ci->u2.nres;  /* just redo 'luaD_poscall' */
686      /* don't need to reset CIST_CLSRET, as it will be set again anyway */
687    }
688    else {
689      int status = LUA_YIELD;  /* default if there were no errors */
690      /* must have a continuation and must be able to call it */
691      lua_assert(ci->u.c.k != NULL && yieldable(L));
692      if (ci->callstatus & CIST_YPCALL)   /* was inside a 'lua_pcallk'? */
693        status = finishpcallk(L, ci);  /* finish it */
694      adjustresults(L, LUA_MULTRET);  /* finish 'lua_callk' */
695      lua_unlock(L);
696      n = (*ci->u.c.k)(L, status, ci->u.c.ctx);  /* call continuation */
697      lua_lock(L);
698      api_checknelems(L, n);
699    }
700    luaD_poscall(L, ci, n);  /* finish 'luaD_call' */
701  }
702  
703  
704  /*
705  ** Executes "full continuation" (everything in the stack) of a
706  ** previously interrupted coroutine until the stack is empty (or another
707  ** interruption long-jumps out of the loop).
708  */
709  static void unroll (lua_State *L, void *ud) {
710    CallInfo *ci;
711    UNUSED(ud);
712    while ((ci = L->ci) != &L->base_ci) {  /* something in the stack */
713      if (!isLua(ci))  /* C function? */
714        finishCcall(L, ci);  /* complete its execution */
715      else {  /* Lua function */
716        luaV_finishOp(L);  /* finish interrupted instruction */
717        luaV_execute(L, ci);  /* execute down to higher C 'boundary' */
718      }
719    }
720  }
721  
722  
723  /*
724  ** Try to find a suspended protected call (a "recover point") for the
725  ** given thread.
726  */
727  static CallInfo *findpcall (lua_State *L) {
728    CallInfo *ci;
729    for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
730      if (ci->callstatus & CIST_YPCALL)
731        return ci;
732    }
733    return NULL;  /* no pending pcall */
734  }
735  
736  
737  /*
738  ** Signal an error in the call to 'lua_resume', not in the execution
739  ** of the coroutine itself. (Such errors should not be handled by any
740  ** coroutine error handler and should not kill the coroutine.)
741  */
742  static int resume_error (lua_State *L, const char *msg, int narg) {
743    L->top -= narg;  /* remove args from the stack */
744    setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
745    api_incr_top(L);
746    lua_unlock(L);
747    return LUA_ERRRUN;
748  }
749  
750  
751  /*
752  ** Do the work for 'lua_resume' in protected mode. Most of the work
753  ** depends on the status of the coroutine: initial state, suspended
754  ** inside a hook, or regularly suspended (optionally with a continuation
755  ** function), plus erroneous cases: non-suspended coroutine or dead
756  ** coroutine.
757  */
758  static void resume (lua_State *L, void *ud) {
759    int n = *(cast(int*, ud));  /* number of arguments */
760    StkId firstArg = L->top - n;  /* first argument */
761    CallInfo *ci = L->ci;
762    if (L->status == LUA_OK)  /* starting a coroutine? */
763      ccall(L, firstArg - 1, LUA_MULTRET, 0);  /* just call its body */
764    else {  /* resuming from previous yield */
765      lua_assert(L->status == LUA_YIELD);
766      L->status = LUA_OK;  /* mark that it is running (again) */
767      if (isLua(ci)) {  /* yielded inside a hook? */
768        L->top = firstArg;  /* discard arguments */
769        luaV_execute(L, ci);  /* just continue running Lua code */
770      }
771      else {  /* 'common' yield */
772        if (ci->u.c.k != NULL) {  /* does it have a continuation function? */
773          lua_unlock(L);
774          n = (*ci->u.c.k)(L, LUA_YIELD, ci->u.c.ctx); /* call continuation */
775          lua_lock(L);
776          api_checknelems(L, n);
777        }
778        luaD_poscall(L, ci, n);  /* finish 'luaD_call' */
779      }
780      unroll(L, NULL);  /* run continuation */
781    }
782  }
783  
784  
785  /*
786  ** Unrolls a coroutine in protected mode while there are recoverable
787  ** errors, that is, errors inside a protected call. (Any error
788  ** interrupts 'unroll', and this loop protects it again so it can
789  ** continue.) Stops with a normal end (status == LUA_OK), an yield
790  ** (status == LUA_YIELD), or an unprotected error ('findpcall' doesn't
791  ** find a recover point).
792  */
793  static int precover (lua_State *L, int status) {
794    CallInfo *ci;
795    while (errorstatus(status) && (ci = findpcall(L)) != NULL) {
796      L->ci = ci;  /* go down to recovery functions */
797      setcistrecst(ci, status);  /* status to finish 'pcall' */
798      status = luaD_rawrunprotected(L, unroll, NULL);
799    }
800    return status;
801  }
802  
803  
804  LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
805                                        int *nresults) {
806    int status;
807    lua_lock(L);
808    if (L->status == LUA_OK) {  /* may be starting a coroutine */
809      if (L->ci != &L->base_ci)  /* not in base level? */
810        return resume_error(L, "cannot resume non-suspended coroutine", nargs);
811      else if (L->top - (L->ci->func + 1) == nargs)  /* no function? */
812        return resume_error(L, "cannot resume dead coroutine", nargs);
813    }
814    else if (L->status != LUA_YIELD)  /* ended with errors? */
815      return resume_error(L, "cannot resume dead coroutine", nargs);
816    L->nCcalls = (from) ? getCcalls(from) : 0;
817    if (getCcalls(L) >= LUAI_MAXCCALLS)
818      return resume_error(L, "C stack overflow", nargs);
819    L->nCcalls++;
820    luai_userstateresume(L, nargs);
821    api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
822    status = luaD_rawrunprotected(L, resume, &nargs);
823     /* continue running after recoverable errors */
824    status = precover(L, status);
825    if (l_likely(!errorstatus(status)))
826      lua_assert(status == L->status);  /* normal end or yield */
827    else {  /* unrecoverable error */
828      L->status = cast_byte(status);  /* mark thread as 'dead' */
829      luaD_seterrorobj(L, status, L->top);  /* push error message */
830      L->ci->top = L->top;
831    }
832    *nresults = (status == LUA_YIELD) ? L->ci->u2.nyield
833                                      : cast_int(L->top - (L->ci->func + 1));
834    lua_unlock(L);
835    return status;
836  }
837  
838  
839  LUA_API int lua_isyieldable (lua_State *L) {
840    return yieldable(L);
841  }
842  
843  
844  LUA_API int lua_yieldk (lua_State *L, int nresults, lua_KContext ctx,
845                          lua_KFunction k) {
846    CallInfo *ci;
847    luai_userstateyield(L, nresults);
848    lua_lock(L);
849    ci = L->ci;
850    api_checknelems(L, nresults);
851    if (l_unlikely(!yieldable(L))) {
852      if (L != G(L)->mainthread)
853        luaG_runerror(L, "attempt to yield across a C-call boundary");
854      else
855        luaG_runerror(L, "attempt to yield from outside a coroutine");
856    }
857    L->status = LUA_YIELD;
858    ci->u2.nyield = nresults;  /* save number of results */
859    if (isLua(ci)) {  /* inside a hook? */
860      lua_assert(!isLuacode(ci));
861      api_check(L, nresults == 0, "hooks cannot yield values");
862      api_check(L, k == NULL, "hooks cannot continue after yielding");
863    }
864    else {
865      if ((ci->u.c.k = k) != NULL)  /* is there a continuation? */
866        ci->u.c.ctx = ctx;  /* save context */
867      luaD_throw(L, LUA_YIELD);
868    }
869    lua_assert(ci->callstatus & CIST_HOOKED);  /* must be inside a hook */
870    lua_unlock(L);
871    return 0;  /* return to 'luaD_hook' */
872  }
873  
874  
875  /*
876  ** Auxiliary structure to call 'luaF_close' in protected mode.
877  */
878  struct CloseP {
879    StkId level;
880    int status;
881  };
882  
883  
884  /*
885  ** Auxiliary function to call 'luaF_close' in protected mode.
886  */
887  static void closepaux (lua_State *L, void *ud) {
888    struct CloseP *pcl = cast(struct CloseP *, ud);
889    luaF_close(L, pcl->level, pcl->status, 0);
890  }
891  
892  
893  /*
894  ** Calls 'luaF_close' in protected mode. Return the original status
895  ** or, in case of errors, the new status.
896  */
897  int luaD_closeprotected (lua_State *L, ptrdiff_t level, int status) {
898    CallInfo *old_ci = L->ci;
899    lu_byte old_allowhooks = L->allowhook;
900    for (;;) {  /* keep closing upvalues until no more errors */
901      struct CloseP pcl;
902      pcl.level = restorestack(L, level); pcl.status = status;
903      status = luaD_rawrunprotected(L, &closepaux, &pcl);
904      if (l_likely(status == LUA_OK))  /* no more errors? */
905        return pcl.status;
906      else {  /* an error occurred; restore saved state and repeat */
907        L->ci = old_ci;
908        L->allowhook = old_allowhooks;
909      }
910    }
911  }
912  
913  
914  /*
915  ** Call the C function 'func' in protected mode, restoring basic
916  ** thread information ('allowhook', etc.) and in particular
917  ** its stack level in case of errors.
918  */
919  int luaD_pcall (lua_State *L, Pfunc func, void *u,
920                  ptrdiff_t old_top, ptrdiff_t ef) {
921    int status;
922    CallInfo *old_ci = L->ci;
923    lu_byte old_allowhooks = L->allowhook;
924    ptrdiff_t old_errfunc = L->errfunc;
925    L->errfunc = ef;
926    status = luaD_rawrunprotected(L, func, u);
927    if (l_unlikely(status != LUA_OK)) {  /* an error occurred? */
928      L->ci = old_ci;
929      L->allowhook = old_allowhooks;
930      status = luaD_closeprotected(L, old_top, status);
931      luaD_seterrorobj(L, status, restorestack(L, old_top));
932      luaD_shrinkstack(L);   /* restore stack size in case of overflow */
933    }
934    L->errfunc = old_errfunc;
935    return status;
936  }
937  
938  
939  
940  /*
941  ** Execute a protected parser.
942  */
943  struct SParser {  /* data to 'f_parser' */
944    ZIO *z;
945    Mbuffer buff;  /* dynamic structure used by the scanner */
946    Dyndata dyd;  /* dynamic structures used by the parser */
947    const char *mode;
948    const char *name;
949  };
950  
951  
952  static void checkmode (lua_State *L, const char *mode, const char *x) {
953    if (mode && strchr(mode, x[0]) == NULL) {
954      luaO_pushfstring(L,
955         "attempt to load a %s chunk (mode is '%s')", x, mode);
956      luaD_throw(L, LUA_ERRSYNTAX);
957    }
958  }
959  
960  
961  static void f_parser (lua_State *L, void *ud) {
962    LClosure *cl;
963    struct SParser *p = cast(struct SParser *, ud);
964    int c = zgetc(p->z);  /* read first character */
965    if (c == LUA_SIGNATURE[0]) {
966      checkmode(L, p->mode, "binary");
967      cl = luaU_undump(L, p->z, p->name);
968    }
969    else {
970      checkmode(L, p->mode, "text");
971      cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
972    }
973    lua_assert(cl->nupvalues == cl->p->sizeupvalues);
974    luaF_initupvals(L, cl);
975  }
976  
977  
978  int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
979                                          const char *mode) {
980    struct SParser p;
981    int status;
982    incnny(L);  /* cannot yield during parsing */
983    p.z = z; p.name = name; p.mode = mode;
984    p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
985    p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
986    p.dyd.label.arr = NULL; p.dyd.label.size = 0;
987    luaZ_initbuffer(L, &p.buff);
988    status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
989    luaZ_freebuffer(L, &p.buff);
990    luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
991    luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
992    luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
993    decnny(L);
994    return status;
995  }
996  
997  
998