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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. 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.