src/lua/ldo.c

   1 /*
   2 ** $Id: ldo.c,v 2.38.1.3 2008/01/18 22:31:22 roberto Exp $
   3 ** Stack and Call structure of Lua
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7
   8 #include <setjmp.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11
  12 #define ldo_c
  13 #define LUA_CORE
  14
  15 #include "lua.h"
  16
  17 #include "ldebug.h"
  18 #include "ldo.h"
  19 #include "lfunc.h"
  20 #include "lgc.h"
  21 #include "lmem.h"
  22 #include "lobject.h"
  23 #include "lopcodes.h"
  24 #include "lparser.h"
  25 #include "lstate.h"
  26 #include "lstring.h"
  27 #include "ltable.h"
  28 #include "ltm.h"
  29 #include "lundump.h"
  30 #include "lvm.h"
  31 #include "lzio.h"
  32
  33
  34
  35
  36 /*
  37 ** {======================================================
  38 ** Error-recovery functions
  39 ** =======================================================
  40 */
  41
  42
  43 /* chain list of long jump buffers */
  44 struct lua_longjmp {
  45   struct lua_longjmp *previous;
  46   luai_jmpbuf b;
  47   volatile int status;  /* error code */
  48 };
  49
  50
  51 void luaD_seterrorobj (lua_State *L, int errcode, StkId oldtop) {
  52   switch (errcode) {
  53     case LUA_ERRMEM: {
  54       setsvalue2s(L, oldtop, luaS_newliteral(L, MEMERRMSG));
  55       break;
  56     }
  57     case LUA_ERRERR: {
  58       setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
  59       break;
  60     }
  61     case LUA_ERRSYNTAX:
  62     case LUA_ERRRUN: {
  63       setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
  64       break;
  65     }
  66   }
  67   L->top = oldtop + 1;
  68 }
  69
  70
  71 static void restore_stack_limit (lua_State *L) {
  72   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK - 1);
  73   if (L->size_ci > LUAI_MAXCALLS) {  /* there was an overflow? */
  74     int inuse = cast_int(L->ci - L->base_ci);
  75     if (inuse + 1 < LUAI_MAXCALLS)  /* can `undo' overflow? */
  76       luaD_reallocCI(L, LUAI_MAXCALLS);
  77   }
  78 }
  79
  80
  81 static void resetstack (lua_State *L, int status) {
  82   L->ci = L->base_ci;
  83   L->base = L->ci->base;
  84   luaF_close(L, L->base);  /* close eventual pending closures */
  85   luaD_seterrorobj(L, status, L->base);
  86   L->nCcalls = L->baseCcalls;
  87   L->allowhook = 1;
  88   restore_stack_limit(L);
  89   L->errfunc = 0;
  90   L->errorJmp = NULL;
  91 }
  92
  93
  94 void luaD_throw (lua_State *L, int errcode) {
  95   if (L->errorJmp) {
  96     L->errorJmp->status = errcode;
  97     LUAI_THROW(L, L->errorJmp);
  98   }
  99   else {
 100     L->status = cast_byte(errcode);
 101     if (G(L)->panic) {
 102       resetstack(L, errcode);
 103       lua_unlock(L);
 104       G(L)->panic(L);
 105     }
 106     exit(EXIT_FAILURE);
 107   }
 108 }
 109
 110
 111 int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 112   struct lua_longjmp lj;
 113   lj.status = 0;
 114   lj.previous = L->errorJmp;  /* chain new error handler */
 115   L->errorJmp = &lj;
 116   LUAI_TRY(L, &lj,
 117     (*f)(L, ud);
 118   );
 119   L->errorJmp = lj.previous;  /* restore old error handler */
 120   return lj.status;
 121 }
 122
 123 /* }====================================================== */
 124
 125
 126 static void correctstack (lua_State *L, TValue *oldstack) {
 127   CallInfo *ci;
 128   GCObject *up;
 129   L->top = (L->top - oldstack) + L->stack;
 130   for (up = L->openupval; up != NULL; up = up->gch.next)
 131     gco2uv(up)->v = (gco2uv(up)->v - oldstack) + L->stack;
 132   for (ci = L->base_ci; ci <= L->ci; ci++) {
 133     ci->top = (ci->top - oldstack) + L->stack;
 134     ci->base = (ci->base - oldstack) + L->stack;
 135     ci->func = (ci->func - oldstack) + L->stack;
 136   }
 137   L->base = (L->base - oldstack) + L->stack;
 138 }
 139
 140
 141 void luaD_reallocstack (lua_State *L, int newsize) {
 142   TValue *oldstack = L->stack;
 143   int realsize = newsize + 1 + EXTRA_STACK;
 144   lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK - 1);
 145   luaM_reallocvector(L, L->stack, L->stacksize, realsize, TValue);
 146   L->stacksize = realsize;
 147   L->stack_last = L->stack+newsize;
 148   correctstack(L, oldstack);
 149 }
 150
 151
 152 void luaD_reallocCI (lua_State *L, int newsize) {
 153   CallInfo *oldci = L->base_ci;
 154   luaM_reallocvector(L, L->base_ci, L->size_ci, newsize, CallInfo);
 155   L->size_ci = newsize;
 156   L->ci = (L->ci - oldci) + L->base_ci;
 157   L->end_ci = L->base_ci + L->size_ci - 1;
 158 }
 159
 160
 161 void luaD_growstack (lua_State *L, int n) {
 162   if (n <= L->stacksize)  /* double size is enough? */
 163     luaD_reallocstack(L, 2*L->stacksize);
 164   else
 165     luaD_reallocstack(L, L->stacksize + n);
 166 }
 167
 168
 169 static CallInfo *growCI (lua_State *L) {
 170   if (L->size_ci > LUAI_MAXCALLS)  /* overflow while handling overflow? */
 171     luaD_throw(L, LUA_ERRERR);
 172   else {
 173     luaD_reallocCI(L, 2*L->size_ci);
 174     if (L->size_ci > LUAI_MAXCALLS)
 175       luaG_runerror(L, "stack overflow");
 176   }
 177   return ++L->ci;
 178 }
 179
 180
 181 void luaD_callhook (lua_State *L, int event, int line) {
 182   lua_Hook hook = L->hook;
 183   if (hook && L->allowhook) {
 184     ptrdiff_t top = savestack(L, L->top);
 185     ptrdiff_t ci_top = savestack(L, L->ci->top);
 186     lua_Debug ar;
 187     ar.event = event;
 188     ar.currentline = line;
 189     if (event == LUA_HOOKTAILRET)
 190       ar.i_ci = 0;  /* tail call; no debug information about it */
 191     else
 192       ar.i_ci = cast_int(L->ci - L->base_ci);
 193     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 194     L->ci->top = L->top + LUA_MINSTACK;
 195     lua_assert(L->ci->top <= L->stack_last);
 196     L->allowhook = 0;  /* cannot call hooks inside a hook */
 197     lua_unlock(L);
 198     (*hook)(L, &ar);
 199     lua_lock(L);
 200     lua_assert(!L->allowhook);
 201     L->allowhook = 1;
 202     L->ci->top = restorestack(L, ci_top);
 203     L->top = restorestack(L, top);
 204   }
 205 }
 206
 207
 208 static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
 209   int i;
 210   int nfixargs = p->numparams;
 211   Table *htab = NULL;
 212   StkId base, fixed;
 213   for (; actual < nfixargs; ++actual)
 214     setnilvalue(L->top++);
 215 #if defined(LUA_COMPAT_VARARG)
 216   if (p->is_vararg & VARARG_NEEDSARG) { /* compat. with old-style vararg? */
 217     int nvar = actual - nfixargs;  /* number of extra arguments */
 218     lua_assert(p->is_vararg & VARARG_HASARG);
 219     luaC_checkGC(L);
 220     htab = luaH_new(L, nvar, 1);  /* create `arg' table */
 221     for (i=0; i<nvar; i++)  /* put extra arguments into `arg' table */
 222       setobj2n(L, luaH_setnum(L, htab, i+1), L->top - nvar + i);
 223     /* store counter in field `n' */
 224     setnvalue(luaH_setstr(L, htab, luaS_newliteral(L, "n")), cast_num(nvar));
 225   }
 226 #endif
 227   /* move fixed parameters to final position */
 228   fixed = L->top - actual;  /* first fixed argument */
 229   base = L->top;  /* final position of first argument */
 230   for (i=0; i<nfixargs; i++) {
 231     setobjs2s(L, L->top++, fixed+i);
 232     setnilvalue(fixed+i);
 233   }
 234   /* add `arg' parameter */
 235   if (htab) {
 236     sethvalue(L, L->top++, htab);
 237     lua_assert(iswhite(obj2gco(htab)));
 238   }
 239   return base;
 240 }
 241
 242
 243 static StkId tryfuncTM (lua_State *L, StkId func) {
 244   const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
 245   StkId p;
 246   ptrdiff_t funcr = savestack(L, func);
 247   if (!ttisfunction(tm))
 248     luaG_typeerror(L, func, "call");
 249   /* Open a hole inside the stack at `func' */
 250   for (p = L->top; p > func; p--) setobjs2s(L, p, p-1);
 251   incr_top(L);
 252   func = restorestack(L, funcr);  /* previous call may change stack */
 253   setobj2s(L, func, tm);  /* tag method is the new function to be called */
 254   return func;
 255 }
 256
 257
 258
 259 #define inc_ci(L) \
 260   ((L->ci == L->end_ci) ? growCI(L) : \
 261    (condhardstacktests(luaD_reallocCI(L, L->size_ci)), ++L->ci))
 262
 263
 264 int luaD_precall (lua_State *L, StkId func, int nresults) {
 265   LClosure *cl;
 266   ptrdiff_t funcr;
 267   if (!ttisfunction(func)) /* `func' is not a function? */
 268     func = tryfuncTM(L, func);  /* check the `function' tag method */
 269   funcr = savestack(L, func);
 270   cl = &clvalue(func)->l;
 271   L->ci->savedpc = L->savedpc;
 272   if (!cl->isC) {  /* Lua function? prepare its call */
 273     CallInfo *ci;
 274     StkId st, base;
 275     Proto *p = cl->p;
 276     luaD_checkstack(L, p->maxstacksize);
 277     func = restorestack(L, funcr);
 278     if (!p->is_vararg) {  /* no varargs? */
 279       base = func + 1;
 280       if (L->top > base + p->numparams)
 281         L->top = base + p->numparams;
 282     }
 283     else {  /* vararg function */
 284       int nargs = cast_int(L->top - func) - 1;
 285       base = adjust_varargs(L, p, nargs);
 286       func = restorestack(L, funcr);  /* previous call may change the stack */
 287     }
 288     ci = inc_ci(L);  /* now `enter' new function */
 289     ci->func = func;
 290     L->base = ci->base = base;
 291     ci->top = L->base + p->maxstacksize;
 292     lua_assert(ci->top <= L->stack_last);
 293     L->savedpc = p->code;  /* starting point */
 294     ci->tailcalls = 0;
 295     ci->nresults = nresults;
 296     for (st = L->top; st < ci->top; st++)
 297       setnilvalue(st);
 298     L->top = ci->top;
 299     if (L->hookmask & LUA_MASKCALL) {
 300       L->savedpc++;  /* hooks assume 'pc' is already incremented */
 301       luaD_callhook(L, LUA_HOOKCALL, -1);
 302       L->savedpc--;  /* correct 'pc' */
 303     }
 304     return PCRLUA;
 305   }
 306   else {  /* if is a C function, call it */
 307     CallInfo *ci;
 308     int n;
 309     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
 310     ci = inc_ci(L);  /* now `enter' new function */
 311     ci->func = restorestack(L, funcr);
 312     L->base = ci->base = ci->func + 1;
 313     ci->top = L->top + LUA_MINSTACK;
 314     lua_assert(ci->top <= L->stack_last);
 315     ci->nresults = nresults;
 316     if (L->hookmask & LUA_MASKCALL)
 317       luaD_callhook(L, LUA_HOOKCALL, -1);
 318     lua_unlock(L);
 319     n = (*curr_func(L)->c.f)(L);  /* do the actual call */
 320     lua_lock(L);
 321     if (n < 0)  /* yielding? */
 322       return PCRYIELD;
 323     else {
 324       luaD_poscall(L, L->top - n);
 325       return PCRC;
 326     }
 327   }
 328 }
 329
 330
 331 static StkId callrethooks (lua_State *L, StkId firstResult) {
 332   ptrdiff_t fr = savestack(L, firstResult);  /* next call may change stack */
 333   luaD_callhook(L, LUA_HOOKRET, -1);
 334   if (f_isLua(L->ci)) {  /* Lua function? */
 335     while ((L->hookmask & LUA_MASKRET) && L->ci->tailcalls--) /* tail calls */
 336       luaD_callhook(L, LUA_HOOKTAILRET, -1);
 337   }
 338   return restorestack(L, fr);
 339 }
 340
 341
 342 int luaD_poscall (lua_State *L, StkId firstResult) {
 343   StkId res;
 344   int wanted, i;
 345   CallInfo *ci;
 346   if (L->hookmask & LUA_MASKRET)
 347     firstResult = callrethooks(L, firstResult);
 348   ci = L->ci--;
 349   res = ci->func;  /* res == final position of 1st result */
 350   wanted = ci->nresults;
 351   L->base = (ci - 1)->base;  /* restore base */
 352   L->savedpc = (ci - 1)->savedpc;  /* restore savedpc */
 353   /* move results to correct place */
 354   for (i = wanted; i != 0 && firstResult < L->top; i--)
 355     setobjs2s(L, res++, firstResult++);
 356   while (i-- > 0)
 357     setnilvalue(res++);
 358   L->top = res;
 359   return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
 360 }
 361
 362
 363 /*
 364 ** Call a function (C or Lua). The function to be called is at *func.
 365 ** The arguments are on the stack, right after the function.
 366 ** When returns, all the results are on the stack, starting at the original
 367 ** function position.
 368 */
 369 void luaD_call (lua_State *L, StkId func, int nResults) {
 370   if (++L->nCcalls >= LUAI_MAXCCALLS) {
 371     if (L->nCcalls == LUAI_MAXCCALLS)
 372       luaG_runerror(L, "C stack overflow");
 373     else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
 374       luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
 375   }
 376   if (luaD_precall(L, func, nResults) == PCRLUA)  /* is a Lua function? */
 377     luaV_execute(L, 1);  /* call it */
 378   L->nCcalls--;
 379   luaC_checkGC(L);
 380 }
 381
 382
 383 static void resume (lua_State *L, void *ud) {
 384   StkId firstArg = cast(StkId, ud);
 385   CallInfo *ci = L->ci;
 386   if (L->status == 0) {  /* start coroutine? */
 387     lua_assert(ci == L->base_ci && firstArg > L->base);
 388     if (luaD_precall(L, firstArg - 1, LUA_MULTRET) != PCRLUA)
 389       return;
 390   }
 391   else {  /* resuming from previous yield */
 392     lua_assert(L->status == LUA_YIELD);
 393     L->status = 0;
 394     if (!f_isLua(ci)) {  /* `common' yield? */
 395       /* finish interrupted execution of `OP_CALL' */
 396       lua_assert(GET_OPCODE(*((ci-1)->savedpc - 1)) == OP_CALL ||
 397                  GET_OPCODE(*((ci-1)->savedpc - 1)) == OP_TAILCALL);
 398       if (luaD_poscall(L, firstArg))  /* complete it... */
 399         L->top = L->ci->top;  /* and correct top if not multiple results */
 400     }
 401     else  /* yielded inside a hook: just continue its execution */
 402       L->base = L->ci->base;
 403   }
 404   luaV_execute(L, cast_int(L->ci - L->base_ci));
 405 }
 406
 407
 408 static int resume_error (lua_State *L, const char *msg) {
 409   L->top = L->ci->base;
 410   setsvalue2s(L, L->top, luaS_new(L, msg));
 411   incr_top(L);
 412   lua_unlock(L);
 413   return LUA_ERRRUN;
 414 }
 415
 416
 417 LUA_API int lua_resume (lua_State *L, int nargs) {
 418   int status;
 419   lua_lock(L);
 420   if (L->status != LUA_YIELD && (L->status != 0 || L->ci != L->base_ci))
 421       return resume_error(L, "cannot resume non-suspended coroutine");
 422   if (L->nCcalls >= LUAI_MAXCCALLS)
 423     return resume_error(L, "C stack overflow");
 424   luai_userstateresume(L, nargs);
 425   lua_assert(L->errfunc == 0);
 426   L->baseCcalls = ++L->nCcalls;
 427   status = luaD_rawrunprotected(L, resume, L->top - nargs);
 428   if (status != 0) {  /* error? */
 429     L->status = cast_byte(status);  /* mark thread as `dead' */
 430     luaD_seterrorobj(L, status, L->top);
 431     L->ci->top = L->top;
 432   }
 433   else {
 434     lua_assert(L->nCcalls == L->baseCcalls);
 435     status = L->status;
 436   }
 437   --L->nCcalls;
 438   lua_unlock(L);
 439   return status;
 440 }
 441
 442
 443 LUA_API int lua_yield (lua_State *L, int nresults) {
 444   luai_userstateyield(L, nresults);
 445   lua_lock(L);
 446   if (L->nCcalls > L->baseCcalls)
 447     luaG_runerror(L, "attempt to yield across metamethod/C-call boundary");
 448   L->base = L->top - nresults;  /* protect stack slots below */
 449   L->status = LUA_YIELD;
 450   lua_unlock(L);
 451   return -1;
 452 }
 453
 454
 455 int luaD_pcall (lua_State *L, Pfunc func, void *u,
 456                 ptrdiff_t old_top, ptrdiff_t ef) {
 457   int status;
 458   unsigned short oldnCcalls = L->nCcalls;
 459   ptrdiff_t old_ci = saveci(L, L->ci);
 460   lu_byte old_allowhooks = L->allowhook;
 461   ptrdiff_t old_errfunc = L->errfunc;
 462   L->errfunc = ef;
 463   status = luaD_rawrunprotected(L, func, u);
 464   if (status != 0) {  /* an error occurred? */
 465     StkId oldtop = restorestack(L, old_top);
 466     luaF_close(L, oldtop);  /* close eventual pending closures */
 467     luaD_seterrorobj(L, status, oldtop);
 468     L->nCcalls = oldnCcalls;
 469     L->ci = restoreci(L, old_ci);
 470     L->base = L->ci->base;
 471     L->savedpc = L->ci->savedpc;
 472     L->allowhook = old_allowhooks;
 473     restore_stack_limit(L);
 474   }
 475   L->errfunc = old_errfunc;
 476   return status;
 477 }
 478
 479
 480
 481 /*
 482 ** Execute a protected parser.
 483 */
 484 struct SParser {  /* data to `f_parser' */
 485   ZIO *z;
 486   Mbuffer buff;  /* buffer to be used by the scanner */
 487   const char *name;
 488 };
 489
 490 static void f_parser (lua_State *L, void *ud) {
 491   int i;
 492   Proto *tf;
 493   Closure *cl;
 494   struct SParser *p = cast(struct SParser *, ud);
 495   int c = luaZ_lookahead(p->z);
 496   luaC_checkGC(L);
 497   tf = ((c == LUA_SIGNATURE[0]) ? luaU_undump : luaY_parser)(L, p->z,
 498                                                              &p->buff, p->name);
 499   cl = luaF_newLclosure(L, tf->nups, hvalue(gt(L)));
 500   cl->l.p = tf;
 501   for (i = 0; i < tf->nups; i++)  /* initialize eventual upvalues */
 502     cl->l.upvals[i] = luaF_newupval(L);
 503   setclvalue(L, L->top, cl);
 504   incr_top(L);
 505 }
 506
 507
 508 int luaD_protectedparser (lua_State *L, ZIO *z, const char *name) {
 509   struct SParser p;
 510   int status;
 511   p.z = z; p.name = name;
 512   luaZ_initbuffer(L, &p.buff);
 513   status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
 514   luaZ_freebuffer(L, &p.buff);
 515   return status;
 516 }
 517
 518