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Member "memcached-1.6.15/vendor/lua/src/ldo.c" (1 Oct 2021, 32454 Bytes) of package /linux/www/memcached-1.6.15.tar.gz:


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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 {
   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 void luaD_tryfuncTM (lua_State *L, StkId func) {
  391   const TValue *tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);
  392   StkId p;
  393   if (l_unlikely(ttisnil(tm)))
  394     luaG_callerror(L, s2v(func));  /* nothing to call */
  395   for (p = L->top; p > func; p--)  /* open space for metamethod */
  396     setobjs2s(L, p, p-1);
  397   L->top++;  /* stack space pre-allocated by the caller */
  398   setobj2s(L, func, tm);  /* metamethod is the new function to be called */
  399 }
  400 
  401 
  402 /*
  403 ** Given 'nres' results at 'firstResult', move 'wanted' of them to 'res'.
  404 ** Handle most typical cases (zero results for commands, one result for
  405 ** expressions, multiple results for tail calls/single parameters)
  406 ** separated.
  407 */
  408 static void moveresults (lua_State *L, StkId res, int nres, int wanted) {
  409   StkId firstresult;
  410   int i;
  411   switch (wanted) {  /* handle typical cases separately */
  412     case 0:  /* no values needed */
  413       L->top = res;
  414       return;
  415     case 1:  /* one value needed */
  416       if (nres == 0)   /* no results? */
  417         setnilvalue(s2v(res));  /* adjust with nil */
  418       else  /* at least one result */
  419         setobjs2s(L, res, L->top - nres);  /* move it to proper place */
  420       L->top = res + 1;
  421       return;
  422     case LUA_MULTRET:
  423       wanted = nres;  /* we want all results */
  424       break;
  425     default:  /* two/more results and/or to-be-closed variables */
  426       if (hastocloseCfunc(wanted)) {  /* to-be-closed variables? */
  427         ptrdiff_t savedres = savestack(L, res);
  428         L->ci->callstatus |= CIST_CLSRET;  /* in case of yields */
  429         L->ci->u2.nres = nres;
  430         luaF_close(L, res, CLOSEKTOP, 1);
  431         L->ci->callstatus &= ~CIST_CLSRET;
  432         if (L->hookmask)  /* if needed, call hook after '__close's */
  433           rethook(L, L->ci, nres);
  434         res = restorestack(L, savedres);  /* close and hook can move stack */
  435         wanted = decodeNresults(wanted);
  436         if (wanted == LUA_MULTRET)
  437           wanted = nres;  /* we want all results */
  438       }
  439       break;
  440   }
  441   /* generic case */
  442   firstresult = L->top - nres;  /* index of first result */
  443   if (nres > wanted)  /* extra results? */
  444     nres = wanted;  /* don't need them */
  445   for (i = 0; i < nres; i++)  /* move all results to correct place */
  446     setobjs2s(L, res + i, firstresult + i);
  447   for (; i < wanted; i++)  /* complete wanted number of results */
  448     setnilvalue(s2v(res + i));
  449   L->top = res + wanted;  /* top points after the last result */
  450 }
  451 
  452 
  453 /*
  454 ** Finishes a function call: calls hook if necessary, moves current
  455 ** number of results to proper place, and returns to previous call
  456 ** info. If function has to close variables, hook must be called after
  457 ** that.
  458 */
  459 void luaD_poscall (lua_State *L, CallInfo *ci, int nres) {
  460   int wanted = ci->nresults;
  461   if (l_unlikely(L->hookmask && !hastocloseCfunc(wanted)))
  462     rethook(L, ci, nres);
  463   /* move results to proper place */
  464   moveresults(L, ci->func, nres, wanted);
  465   /* function cannot be in any of these cases when returning */
  466   lua_assert(!(ci->callstatus &
  467         (CIST_HOOKED | CIST_YPCALL | CIST_FIN | CIST_TRAN | CIST_CLSRET)));
  468   L->ci = ci->previous;  /* back to caller (after closing variables) */
  469 }
  470 
  471 
  472 
  473 #define next_ci(L)  (L->ci->next ? L->ci->next : luaE_extendCI(L))
  474 
  475 
  476 /*
  477 ** Prepare a function for a tail call, building its call info on top
  478 ** of the current call info. 'narg1' is the number of arguments plus 1
  479 ** (so that it includes the function itself).
  480 */
  481 void luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func, int narg1) {
  482   Proto *p = clLvalue(s2v(func))->p;
  483   int fsize = p->maxstacksize;  /* frame size */
  484   int nfixparams = p->numparams;
  485   int i;
  486   for (i = 0; i < narg1; i++)  /* move down function and arguments */
  487     setobjs2s(L, ci->func + i, func + i);
  488   checkstackGC(L, fsize);
  489   func = ci->func;  /* moved-down function */
  490   for (; narg1 <= nfixparams; narg1++)
  491     setnilvalue(s2v(func + narg1));  /* complete missing arguments */
  492   ci->top = func + 1 + fsize;  /* top for new function */
  493   lua_assert(ci->top <= L->stack_last);
  494   ci->u.l.savedpc = p->code;  /* starting point */
  495   ci->callstatus |= CIST_TAIL;
  496   L->top = func + narg1;  /* set top */
  497 }
  498 
  499 
  500 /*
  501 ** Prepares the call to a function (C or Lua). For C functions, also do
  502 ** the call. The function to be called is at '*func'.  The arguments
  503 ** are on the stack, right after the function.  Returns the CallInfo
  504 ** to be executed, if it was a Lua function. Otherwise (a C function)
  505 ** returns NULL, with all the results on the stack, starting at the
  506 ** original function position.
  507 */
  508 CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
  509   lua_CFunction f;
  510  retry:
  511   switch (ttypetag(s2v(func))) {
  512     case LUA_VCCL:  /* C closure */
  513       f = clCvalue(s2v(func))->f;
  514       goto Cfunc;
  515     case LUA_VLCF:  /* light C function */
  516       f = fvalue(s2v(func));
  517      Cfunc: {
  518       int n;  /* number of returns */
  519       CallInfo *ci;
  520       checkstackGCp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
  521       L->ci = ci = next_ci(L);
  522       ci->nresults = nresults;
  523       ci->callstatus = CIST_C;
  524       ci->top = L->top + LUA_MINSTACK;
  525       ci->func = func;
  526       lua_assert(ci->top <= L->stack_last);
  527       if (l_unlikely(L->hookmask & LUA_MASKCALL)) {
  528         int narg = cast_int(L->top - func) - 1;
  529         luaD_hook(L, LUA_HOOKCALL, -1, 1, narg);
  530       }
  531       lua_unlock(L);
  532       n = (*f)(L);  /* do the actual call */
  533       lua_lock(L);
  534       api_checknelems(L, n);
  535       luaD_poscall(L, ci, n);
  536       return NULL;
  537     }
  538     case LUA_VLCL: {  /* Lua function */
  539       CallInfo *ci;
  540       Proto *p = clLvalue(s2v(func))->p;
  541       int narg = cast_int(L->top - func) - 1;  /* number of real arguments */
  542       int nfixparams = p->numparams;
  543       int fsize = p->maxstacksize;  /* frame size */
  544       checkstackGCp(L, fsize, func);
  545       L->ci = ci = next_ci(L);
  546       ci->nresults = nresults;
  547       ci->u.l.savedpc = p->code;  /* starting point */
  548       ci->top = func + 1 + fsize;
  549       ci->func = func;
  550       L->ci = ci;
  551       for (; narg < nfixparams; narg++)
  552         setnilvalue(s2v(L->top++));  /* complete missing arguments */
  553       lua_assert(ci->top <= L->stack_last);
  554       return ci;
  555     }
  556     default: {  /* not a function */
  557       checkstackGCp(L, 1, func);  /* space for metamethod */
  558       luaD_tryfuncTM(L, func);  /* try to get '__call' metamethod */
  559       goto retry;  /* try again with metamethod */
  560     }
  561   }
  562 }
  563 
  564 
  565 /*
  566 ** Call a function (C or Lua) through C. 'inc' can be 1 (increment
  567 ** number of recursive invocations in the C stack) or nyci (the same
  568 ** plus increment number of non-yieldable calls).
  569 */
  570 static void ccall (lua_State *L, StkId func, int nResults, int inc) {
  571   CallInfo *ci;
  572   L->nCcalls += inc;
  573   if (l_unlikely(getCcalls(L) >= LUAI_MAXCCALLS))
  574     luaE_checkcstack(L);
  575   if ((ci = luaD_precall(L, func, nResults)) != NULL) {  /* Lua function? */
  576     ci->callstatus = CIST_FRESH;  /* mark that it is a "fresh" execute */
  577     luaV_execute(L, ci);  /* call it */
  578   }
  579   L->nCcalls -= inc;
  580 }
  581 
  582 
  583 /*
  584 ** External interface for 'ccall'
  585 */
  586 void luaD_call (lua_State *L, StkId func, int nResults) {
  587   ccall(L, func, nResults, 1);
  588 }
  589 
  590 
  591 /*
  592 ** Similar to 'luaD_call', but does not allow yields during the call.
  593 */
  594 void luaD_callnoyield (lua_State *L, StkId func, int nResults) {
  595   ccall(L, func, nResults, nyci);
  596 }
  597 
  598 
  599 /*
  600 ** Finish the job of 'lua_pcallk' after it was interrupted by an yield.
  601 ** (The caller, 'finishCcall', does the final call to 'adjustresults'.)
  602 ** The main job is to complete the 'luaD_pcall' called by 'lua_pcallk'.
  603 ** If a '__close' method yields here, eventually control will be back
  604 ** to 'finishCcall' (when that '__close' method finally returns) and
  605 ** 'finishpcallk' will run again and close any still pending '__close'
  606 ** methods. Similarly, if a '__close' method errs, 'precover' calls
  607 ** 'unroll' which calls ''finishCcall' and we are back here again, to
  608 ** close any pending '__close' methods.
  609 ** Note that, up to the call to 'luaF_close', the corresponding
  610 ** 'CallInfo' is not modified, so that this repeated run works like the
  611 ** first one (except that it has at least one less '__close' to do). In
  612 ** particular, field CIST_RECST preserves the error status across these
  613 ** multiple runs, changing only if there is a new error.
  614 */
  615 static int finishpcallk (lua_State *L,  CallInfo *ci) {
  616   int status = getcistrecst(ci);  /* get original status */
  617   if (l_likely(status == LUA_OK))  /* no error? */
  618     status = LUA_YIELD;  /* was interrupted by an yield */
  619   else {  /* error */
  620     StkId func = restorestack(L, ci->u2.funcidx);
  621     L->allowhook = getoah(ci->callstatus);  /* restore 'allowhook' */
  622     luaF_close(L, func, status, 1);  /* can yield or raise an error */
  623     func = restorestack(L, ci->u2.funcidx);  /* stack may be moved */
  624     luaD_seterrorobj(L, status, func);
  625     luaD_shrinkstack(L);   /* restore stack size in case of overflow */
  626     setcistrecst(ci, LUA_OK);  /* clear original status */
  627   }
  628   ci->callstatus &= ~CIST_YPCALL;
  629   L->errfunc = ci->u.c.old_errfunc;
  630   /* if it is here, there were errors or yields; unlike 'lua_pcallk',
  631      do not change status */
  632   return status;
  633 }
  634 
  635 
  636 /*
  637 ** Completes the execution of a C function interrupted by an yield.
  638 ** The interruption must have happened while the function was either
  639 ** closing its tbc variables in 'moveresults' or executing
  640 ** 'lua_callk'/'lua_pcallk'. In the first case, it just redoes
  641 ** 'luaD_poscall'. In the second case, the call to 'finishpcallk'
  642 ** finishes the interrupted execution of 'lua_pcallk'.  After that, it
  643 ** calls the continuation of the interrupted function and finally it
  644 ** completes the job of the 'luaD_call' that called the function.  In
  645 ** the call to 'adjustresults', we do not know the number of results
  646 ** of the function called by 'lua_callk'/'lua_pcallk', so we are
  647 ** conservative and use LUA_MULTRET (always adjust).
  648 */
  649 static void finishCcall (lua_State *L, CallInfo *ci) {
  650   int n;  /* actual number of results from C function */
  651   if (ci->callstatus & CIST_CLSRET) {  /* was returning? */
  652     lua_assert(hastocloseCfunc(ci->nresults));
  653     n = ci->u2.nres;  /* just redo 'luaD_poscall' */
  654     /* don't need to reset CIST_CLSRET, as it will be set again anyway */
  655   }
  656   else {
  657     int status = LUA_YIELD;  /* default if there were no errors */
  658     /* must have a continuation and must be able to call it */
  659     lua_assert(ci->u.c.k != NULL && yieldable(L));
  660     if (ci->callstatus & CIST_YPCALL)   /* was inside a 'lua_pcallk'? */
  661       status = finishpcallk(L, ci);  /* finish it */
  662     adjustresults(L, LUA_MULTRET);  /* finish 'lua_callk' */
  663     lua_unlock(L);
  664     n = (*ci->u.c.k)(L, status, ci->u.c.ctx);  /* call continuation */
  665     lua_lock(L);
  666     api_checknelems(L, n);
  667   }
  668   luaD_poscall(L, ci, n);  /* finish 'luaD_call' */
  669 }
  670 
  671 
  672 /*
  673 ** Executes "full continuation" (everything in the stack) of a
  674 ** previously interrupted coroutine until the stack is empty (or another
  675 ** interruption long-jumps out of the loop).
  676 */
  677 static void unroll (lua_State *L, void *ud) {
  678   CallInfo *ci;
  679   UNUSED(ud);
  680   while ((ci = L->ci) != &L->base_ci) {  /* something in the stack */
  681     if (!isLua(ci))  /* C function? */
  682       finishCcall(L, ci);  /* complete its execution */
  683     else {  /* Lua function */
  684       luaV_finishOp(L);  /* finish interrupted instruction */
  685       luaV_execute(L, ci);  /* execute down to higher C 'boundary' */
  686     }
  687   }
  688 }
  689 
  690 
  691 /*
  692 ** Try to find a suspended protected call (a "recover point") for the
  693 ** given thread.
  694 */
  695 static CallInfo *findpcall (lua_State *L) {
  696   CallInfo *ci;
  697   for (ci = L->ci; ci != NULL; ci = ci->previous) {  /* search for a pcall */
  698     if (ci->callstatus & CIST_YPCALL)
  699       return ci;
  700   }
  701   return NULL;  /* no pending pcall */
  702 }
  703 
  704 
  705 /*
  706 ** Signal an error in the call to 'lua_resume', not in the execution
  707 ** of the coroutine itself. (Such errors should not be handled by any
  708 ** coroutine error handler and should not kill the coroutine.)
  709 */
  710 static int resume_error (lua_State *L, const char *msg, int narg) {
  711   L->top -= narg;  /* remove args from the stack */
  712   setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
  713   api_incr_top(L);
  714   lua_unlock(L);
  715   return LUA_ERRRUN;
  716 }
  717 
  718 
  719 /*
  720 ** Do the work for 'lua_resume' in protected mode. Most of the work
  721 ** depends on the status of the coroutine: initial state, suspended
  722 ** inside a hook, or regularly suspended (optionally with a continuation
  723 ** function), plus erroneous cases: non-suspended coroutine or dead
  724 ** coroutine.
  725 */
  726 static void resume (lua_State *L, void *ud) {
  727   int n = *(cast(int*, ud));  /* number of arguments */
  728   StkId firstArg = L->top - n;  /* first argument */
  729   CallInfo *ci = L->ci;
  730   if (L->status == LUA_OK)  /* starting a coroutine? */
  731     ccall(L, firstArg - 1, LUA_MULTRET, 1);  /* just call its body */
  732   else {  /* resuming from previous yield */
  733     lua_assert(L->status == LUA_YIELD);
  734     L->status = LUA_OK;  /* mark that it is running (again) */
  735     luaE_incCstack(L);  /* control the C stack */
  736     if (isLua(ci)) {  /* yielded inside a hook? */
  737       L->top = firstArg;  /* discard arguments */
  738       luaV_execute(L, ci);  /* just continue running Lua code */
  739     }
  740     else {  /* 'common' yield */
  741       if (ci->u.c.k != NULL) {  /* does it have a continuation function? */
  742         lua_unlock(L);
  743         n = (*ci->u.c.k)(L, LUA_YIELD, ci->u.c.ctx); /* call continuation */
  744         lua_lock(L);
  745         api_checknelems(L, n);
  746       }
  747       luaD_poscall(L, ci, n);  /* finish 'luaD_call' */
  748     }
  749     unroll(L, NULL);  /* run continuation */
  750   }
  751 }
  752 
  753 
  754 /*
  755 ** Unrolls a coroutine in protected mode while there are recoverable
  756 ** errors, that is, errors inside a protected call. (Any error
  757 ** interrupts 'unroll', and this loop protects it again so it can
  758 ** continue.) Stops with a normal end (status == LUA_OK), an yield
  759 ** (status == LUA_YIELD), or an unprotected error ('findpcall' doesn't
  760 ** find a recover point).
  761 */
  762 static int precover (lua_State *L, int status) {
  763   CallInfo *ci;
  764   while (errorstatus(status) && (ci = findpcall(L)) != NULL) {
  765     L->ci = ci;  /* go down to recovery functions */
  766     setcistrecst(ci, status);  /* status to finish 'pcall' */
  767     status = luaD_rawrunprotected(L, unroll, NULL);
  768   }
  769   return status;
  770 }
  771 
  772 
  773 LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
  774                                       int *nresults) {
  775   int status;
  776   lua_lock(L);
  777   if (L->status == LUA_OK) {  /* may be starting a coroutine */
  778     if (L->ci != &L->base_ci)  /* not in base level? */
  779       return resume_error(L, "cannot resume non-suspended coroutine", nargs);
  780     else if (L->top - (L->ci->func + 1) == nargs)  /* no function? */
  781       return resume_error(L, "cannot resume dead coroutine", nargs);
  782   }
  783   else if (L->status != LUA_YIELD)  /* ended with errors? */
  784     return resume_error(L, "cannot resume dead coroutine", nargs);
  785   L->nCcalls = (from) ? getCcalls(from) : 0;
  786   luai_userstateresume(L, nargs);
  787   api_checknelems(L, (L->status == LUA_OK) ? nargs + 1 : nargs);
  788   status = luaD_rawrunprotected(L, resume, &nargs);
  789    /* continue running after recoverable errors */
  790   status = precover(L, status);
  791   if (l_likely(!errorstatus(status)))
  792     lua_assert(status == L->status);  /* normal end or yield */
  793   else {  /* unrecoverable error */
  794     L->status = cast_byte(status);  /* mark thread as 'dead' */
  795     luaD_seterrorobj(L, status, L->top);  /* push error message */
  796     L->ci->top = L->top;
  797   }
  798   *nresults = (status == LUA_YIELD) ? L->ci->u2.nyield
  799                                     : cast_int(L->top - (L->ci->func + 1));
  800   lua_unlock(L);
  801   return status;
  802 }
  803 
  804 
  805 LUA_API int lua_isyieldable (lua_State *L) {
  806   return yieldable(L);
  807 }
  808 
  809 
  810 LUA_API int lua_yieldk (lua_State *L, int nresults, lua_KContext ctx,
  811                         lua_KFunction k) {
  812   CallInfo *ci;
  813   luai_userstateyield(L, nresults);
  814   lua_lock(L);
  815   ci = L->ci;
  816   api_checknelems(L, nresults);
  817   if (l_unlikely(!yieldable(L))) {
  818     if (L != G(L)->mainthread)
  819       luaG_runerror(L, "attempt to yield across a C-call boundary");
  820     else
  821       luaG_runerror(L, "attempt to yield from outside a coroutine");
  822   }
  823   L->status = LUA_YIELD;
  824   ci->u2.nyield = nresults;  /* save number of results */
  825   if (isLua(ci)) {  /* inside a hook? */
  826     lua_assert(!isLuacode(ci));
  827     api_check(L, nresults == 0, "hooks cannot yield values");
  828     api_check(L, k == NULL, "hooks cannot continue after yielding");
  829   }
  830   else {
  831     if ((ci->u.c.k = k) != NULL)  /* is there a continuation? */
  832       ci->u.c.ctx = ctx;  /* save context */
  833     luaD_throw(L, LUA_YIELD);
  834   }
  835   lua_assert(ci->callstatus & CIST_HOOKED);  /* must be inside a hook */
  836   lua_unlock(L);
  837   return 0;  /* return to 'luaD_hook' */
  838 }
  839 
  840 
  841 /*
  842 ** Auxiliary structure to call 'luaF_close' in protected mode.
  843 */
  844 struct CloseP {
  845   StkId level;
  846   int status;
  847 };
  848 
  849 
  850 /*
  851 ** Auxiliary function to call 'luaF_close' in protected mode.
  852 */
  853 static void closepaux (lua_State *L, void *ud) {
  854   struct CloseP *pcl = cast(struct CloseP *, ud);
  855   luaF_close(L, pcl->level, pcl->status, 0);
  856 }
  857 
  858 
  859 /*
  860 ** Calls 'luaF_close' in protected mode. Return the original status
  861 ** or, in case of errors, the new status.
  862 */
  863 int luaD_closeprotected (lua_State *L, ptrdiff_t level, int status) {
  864   CallInfo *old_ci = L->ci;
  865   lu_byte old_allowhooks = L->allowhook;
  866   for (;;) {  /* keep closing upvalues until no more errors */
  867     struct CloseP pcl;
  868     pcl.level = restorestack(L, level); pcl.status = status;
  869     status = luaD_rawrunprotected(L, &closepaux, &pcl);
  870     if (l_likely(status == LUA_OK))  /* no more errors? */
  871       return pcl.status;
  872     else {  /* an error occurred; restore saved state and repeat */
  873       L->ci = old_ci;
  874       L->allowhook = old_allowhooks;
  875     }
  876   }
  877 }
  878 
  879 
  880 /*
  881 ** Call the C function 'func' in protected mode, restoring basic
  882 ** thread information ('allowhook', etc.) and in particular
  883 ** its stack level in case of errors.
  884 */
  885 int luaD_pcall (lua_State *L, Pfunc func, void *u,
  886                 ptrdiff_t old_top, ptrdiff_t ef) {
  887   int status;
  888   CallInfo *old_ci = L->ci;
  889   lu_byte old_allowhooks = L->allowhook;
  890   ptrdiff_t old_errfunc = L->errfunc;
  891   L->errfunc = ef;
  892   status = luaD_rawrunprotected(L, func, u);
  893   if (l_unlikely(status != LUA_OK)) {  /* an error occurred? */
  894     L->ci = old_ci;
  895     L->allowhook = old_allowhooks;
  896     status = luaD_closeprotected(L, old_top, status);
  897     luaD_seterrorobj(L, status, restorestack(L, old_top));
  898     luaD_shrinkstack(L);   /* restore stack size in case of overflow */
  899   }
  900   L->errfunc = old_errfunc;
  901   return status;
  902 }
  903 
  904 
  905 
  906 /*
  907 ** Execute a protected parser.
  908 */
  909 struct SParser {  /* data to 'f_parser' */
  910   ZIO *z;
  911   Mbuffer buff;  /* dynamic structure used by the scanner */
  912   Dyndata dyd;  /* dynamic structures used by the parser */
  913   const char *mode;
  914   const char *name;
  915 };
  916 
  917 
  918 static void checkmode (lua_State *L, const char *mode, const char *x) {
  919   if (mode && strchr(mode, x[0]) == NULL) {
  920     luaO_pushfstring(L,
  921        "attempt to load a %s chunk (mode is '%s')", x, mode);
  922     luaD_throw(L, LUA_ERRSYNTAX);
  923   }
  924 }
  925 
  926 
  927 static void f_parser (lua_State *L, void *ud) {
  928   LClosure *cl;
  929   struct SParser *p = cast(struct SParser *, ud);
  930   int c = zgetc(p->z);  /* read first character */
  931   if (c == LUA_SIGNATURE[0]) {
  932     checkmode(L, p->mode, "binary");
  933     cl = luaU_undump(L, p->z, p->name);
  934   }
  935   else {
  936     checkmode(L, p->mode, "text");
  937     cl = luaY_parser(L, p->z, &p->buff, &p->dyd, p->name, c);
  938   }
  939   lua_assert(cl->nupvalues == cl->p->sizeupvalues);
  940   luaF_initupvals(L, cl);
  941 }
  942 
  943 
  944 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
  945                                         const char *mode) {
  946   struct SParser p;
  947   int status;
  948   incnny(L);  /* cannot yield during parsing */
  949   p.z = z; p.name = name; p.mode = mode;
  950   p.dyd.actvar.arr = NULL; p.dyd.actvar.size = 0;
  951   p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
  952   p.dyd.label.arr = NULL; p.dyd.label.size = 0;
  953   luaZ_initbuffer(L, &p.buff);
  954   status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
  955   luaZ_freebuffer(L, &p.buff);
  956   luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
  957   luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
  958   luaM_freearray(L, p.dyd.label.arr, p.dyd.label.size);
  959   decnny(L);
  960   return status;
  961 }
  962 
  963