text: /*
  ** $Id: ldo.c,v 2.38.1.4 2012/01/18 02:27:10 roberto Exp $
  ** Stack and Call structure of Lua
  ** See Copyright Notice in lua.h
  */
  
  
  #include <setjmp.h>
  #include <stdlib.h>
  #include <string.h>
  
  #define ldo_c
  #define LUA_CORE
  
  #include "lua.h"
  
  #include "ldebug.h"
  #include "ldo.h"
  #include "lfunc.h"
  #include "lgc.h"
  #include "lmem.h"
  #include "lobject.h"
  #include "lopcodes.h"
  #include "lparser.h"
  #include "lstate.h"
  #include "lstring.h"
  #include "ltable.h"
  #include "ltm.h"
  #include "lundump.h"
  #include "lvm.h"
  #include "lzio.h"
  
  
  
  
  /*
  ** {======================================================
  ** Error-recovery functions
  ** =======================================================
  */
  
  
  /* chain list of long jump buffers */
  struct lua_longjmp {
    struct lua_longjmp *previous;
    luai_jmpbuf b;
    volatile int status;  /* error code */
  };
  
  
  void luaD_seterrorobj (lua_State *L, int errcode, StkId oldtop) {
    switch (errcode) {
      case LUA_ERRMEM: {
        setsvalue2s(L, oldtop, luaS_newliteral(L, MEMERRMSG));
        break;
      }
      case LUA_ERRERR: {
        setsvalue2s(L, oldtop, luaS_newliteral(L, "error in error handling"));
        break;
      }
      case LUA_ERRSYNTAX:
      case LUA_ERRRUN: {
        setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
        break;
      }
    }
    L->top = oldtop + 1;
  }
  
  
  static void restore_stack_limit (lua_State *L) {
    lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK - 1);
    if (L->size_ci > LUAI_MAXCALLS) {  /* there was an overflow? */
      int inuse = cast_int(L->ci - L->base_ci);
      if (inuse + 1 < LUAI_MAXCALLS)  /* can `undo' overflow? */
        luaD_reallocCI(L, LUAI_MAXCALLS);
    }
  }
  
  
  static void resetstack (lua_State *L, int status) {
    L->ci = L->base_ci;
    L->base = L->ci->base;
    luaF_close(L, L->base);  /* close eventual pending closures */
    luaD_seterrorobj(L, status, L->base);
    L->nCcalls = L->baseCcalls;
    L->allowhook = 1;
    restore_stack_limit(L);
    L->errfunc = 0;
    L->errorJmp = NULL;
  }
  
  
  void luaD_throw (lua_State *L, int errcode) {
    if (L->errorJmp) {
      L->errorJmp->status = errcode;
      LUAI_THROW(L, L->errorJmp);
    }
    else {
      L->status = cast_byte(errcode);
      if (G(L)->panic) {
        resetstack(L, errcode);
        lua_unlock(L);
        G(L)->panic(L);
      }
      exit(EXIT_FAILURE);
    }
  }
  
  
  int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
    struct lua_longjmp lj;
    lj.status = 0;
    lj.previous = L->errorJmp;  /* chain new error handler */
    L->errorJmp = &lj;
    LUAI_TRY(L, &lj,
      (*f)(L, ud);
    );
    L->errorJmp = lj.previous;  /* restore old error handler */
    return lj.status;
  }
  
  /* }====================================================== */
  
  
  static void correctstack (lua_State *L, TValue *oldstack) {
    CallInfo *ci;
    GCObject *up;
    L->top = (L->top - oldstack) + L->stack;
    for (up = L->openupval; up != NULL; up = up->gch.next)
      gco2uv(up)->v = (gco2uv(up)->v - oldstack) + L->stack;
    for (ci = L->base_ci; ci <= L->ci; ci++) {
      ci->top = (ci->top - oldstack) + L->stack;
      ci->base = (ci->base - oldstack) + L->stack;
      ci->func = (ci->func - oldstack) + L->stack;
    }
    L->base = (L->base - oldstack) + L->stack;
  }
  
  
  void luaD_reallocstack (lua_State *L, int newsize) {
    TValue *oldstack = L->stack;
    int realsize = newsize + 1 + EXTRA_STACK;
    lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK - 1);
    luaM_reallocvector(L, L->stack, L->stacksize, realsize, TValue);
    L->stacksize = realsize;
    L->stack_last = L->stack+newsize;
    correctstack(L, oldstack);
  }
  
  
  void luaD_reallocCI (lua_State *L, int newsize) {
    CallInfo *oldci = L->base_ci;
    luaM_reallocvector(L, L->base_ci, L->size_ci, newsize, CallInfo);
    L->size_ci = newsize;
    L->ci = (L->ci - oldci) + L->base_ci;
    L->end_ci = L->base_ci + L->size_ci - 1;
  }
  
  
  void luaD_growstack (lua_State *L, int n) {
    if (n <= L->stacksize)  /* double size is enough? */
      luaD_reallocstack(L, 2*L->stacksize);
    else
      luaD_reallocstack(L, L->stacksize + n);
  }
  
  
  static CallInfo *growCI (lua_State *L) {
    if (L->size_ci > LUAI_MAXCALLS)  /* overflow while handling overflow? */
      luaD_throw(L, LUA_ERRERR);
    else {
      luaD_reallocCI(L, 2*L->size_ci);
      if (L->size_ci > LUAI_MAXCALLS)
        luaG_runerror(L, "stack overflow");
    }
    return ++L->ci;
  }
  
  
  void luaD_callhook (lua_State *L, int event, int line) {
    lua_Hook hook = L->hook;
    if (hook && L->allowhook) {
      ptrdiff_t top = savestack(L, L->top);
      ptrdiff_t ci_top = savestack(L, L->ci->top);
      lua_Debug ar;
      ar.event = event;
      ar.currentline = line;
      if (event == LUA_HOOKTAILRET)
        ar.i_ci = 0;  /* tail call; no debug information about it */
      else
        ar.i_ci = cast_int(L->ci - L->base_ci);
      luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
      L->ci->top = L->top + LUA_MINSTACK;
      lua_assert(L->ci->top <= L->stack_last);
      L->allowhook = 0;  /* cannot call hooks inside a hook */
      lua_unlock(L);
      (*hook)(L, &ar);
      lua_lock(L);
      lua_assert(!L->allowhook);
      L->allowhook = 1;
      L->ci->top = restorestack(L, ci_top);
      L->top = restorestack(L, top);
    }
  }
  
  
  static StkId adjust_varargs (lua_State *L, Proto *p, int actual) {
    int i;
    int nfixargs = p->numparams;
    Table *htab = NULL;
    StkId base, fixed;
    for (; actual < nfixargs; ++actual)
      setnilvalue(L->top++);
  #if defined(LUA_COMPAT_VARARG)
    if (p->is_vararg & VARARG_NEEDSARG) { /* compat. with old-style vararg? */
      int nvar = actual - nfixargs;  /* number of extra arguments */
      lua_assert(p->is_vararg & VARARG_HASARG);
      luaC_checkGC(L);
      luaD_checkstack(L, p->maxstacksize);
      htab = luaH_new(L, nvar, 1);  /* create `arg' table */
      for (i=0; i<nvar; i++)  /* put extra arguments into `arg' table */
        setobj2n(L, luaH_setnum(L, htab, i+1), L->top - nvar + i);
      /* store counter in field `n' */
      setnvalue(luaH_setstr(L, htab, luaS_newliteral(L, "n")), cast_num(nvar));
    }
  #endif
    /* move fixed parameters to final position */
    fixed = L->top - actual;  /* first fixed argument */
    base = L->top;  /* final position of first argument */
    for (i=0; i<nfixargs; i++) {
      setobjs2s(L, L->top++, fixed+i);
      setnilvalue(fixed+i);
    }
    /* add `arg' parameter */
    if (htab) {
      sethvalue(L, L->top++, htab);
      lua_assert(iswhite(obj2gco(htab)));
    }
    return base;
  }
  
  
  static StkId tryfuncTM (lua_State *L, StkId func) {
    const TValue *tm = luaT_gettmbyobj(L, func, TM_CALL);
    StkId p;
    ptrdiff_t funcr = savestack(L, func);
    if (!ttisfunction(tm))
      luaG_typeerror(L, func, "call");
    /* Open a hole inside the stack at `func' */
    for (p = L->top; p > func; p--) setobjs2s(L, p, p-1);
    incr_top(L);
    func = restorestack(L, funcr);  /* previous call may change stack */
    setobj2s(L, func, tm);  /* tag method is the new function to be called */
    return func;
  }
  
  
  
  #define inc_ci(L) \
    ((L->ci == L->end_ci) ? growCI(L) : \
     (condhardstacktests(luaD_reallocCI(L, L->size_ci)), ++L->ci))
  
  
  int luaD_precall (lua_State *L, StkId func, int nresults) {
    LClosure *cl;
    ptrdiff_t funcr;
    if (!ttisfunction(func)) /* `func' is not a function? */
      func = tryfuncTM(L, func);  /* check the `function' tag method */
    funcr = savestack(L, func);
    cl = &clvalue(func)->l;
    L->ci->savedpc = L->savedpc;
    if (!cl->isC) {  /* Lua function? prepare its call */
      CallInfo *ci;
      StkId st, base;
      Proto *p = cl->p;
      luaD_checkstack(L, p->maxstacksize);
      func = restorestack(L, funcr);
      if (!p->is_vararg) {  /* no varargs? */
        base = func + 1;
        if (L->top > base + p->numparams)
          L->top = base + p->numparams;
      }
      else {  /* vararg function */
        int nargs = cast_int(L->top - func) - 1;
        base = adjust_varargs(L, p, nargs);
        func = restorestack(L, funcr);  /* previous call may change the stack */
      }
      ci = inc_ci(L);  /* now `enter' new function */
      ci->func = func;
      L->base = ci->base = base;
      ci->top = L->base + p->maxstacksize;
      lua_assert(ci->top <= L->stack_last);
      L->savedpc = p->code;  /* starting point */
      ci->tailcalls = 0;
      ci->nresults = nresults;
      for (st = L->top; st < ci->top; st++)
        setnilvalue(st);
      L->top = ci->top;
      if (L->hookmask & LUA_MASKCALL) {
        L->savedpc++;  /* hooks assume 'pc' is already incremented */
        luaD_callhook(L, LUA_HOOKCALL, -1);
        L->savedpc--;  /* correct 'pc' */
      }
      return PCRLUA;
    }
    else {  /* if is a C function, call it */
      CallInfo *ci;
      int n;
      luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
      ci = inc_ci(L);  /* now `enter' new function */
      ci->func = restorestack(L, funcr);
      L->base = ci->base = ci->func + 1;
      ci->top = L->top + LUA_MINSTACK;
      lua_assert(ci->top <= L->stack_last);
      ci->nresults = nresults;
      if (L->hookmask & LUA_MASKCALL)
        luaD_callhook(L, LUA_HOOKCALL, -1);
      lua_unlock(L);
      n = (*curr_func(L)->c.f)(L);  /* do the actual call */
      lua_lock(L);
      if (n < 0)  /* yielding? */
        return PCRYIELD;
      else {
        luaD_poscall(L, L->top - n);
        return PCRC;
      }
    }
  }
  
  
  static StkId callrethooks (lua_State *L, StkId firstResult) {
    ptrdiff_t fr = savestack(L, firstResult);  /* next call may change stack */
    luaD_callhook(L, LUA_HOOKRET, -1);
    if (f_isLua(L->ci)) {  /* Lua function? */
      while ((L->hookmask & LUA_MASKRET) && L->ci->tailcalls--) /* tail calls */
        luaD_callhook(L, LUA_HOOKTAILRET, -1);
    }
    return restorestack(L, fr);
  }
  
  
  int luaD_poscall (lua_State *L, StkId firstResult) {
    StkId res;
    int wanted, i;
    CallInfo *ci;
    if (L->hookmask & LUA_MASKRET)
      firstResult = callrethooks(L, firstResult);
    ci = L->ci--;
    res = ci->func;  /* res == final position of 1st result */
    wanted = ci->nresults;
    L->base = (ci - 1)->base;  /* restore base */
    L->savedpc = (ci - 1)->savedpc;  /* restore savedpc */
    /* move results to correct place */
    for (i = wanted; i != 0 && firstResult < L->top; i--)
      setobjs2s(L, res++, firstResult++);
    while (i-- > 0)
      setnilvalue(res++);
    L->top = res;
    return (wanted - LUA_MULTRET);  /* 0 iff wanted == LUA_MULTRET */
  }
  
  
  /*
  ** Call a function (C or Lua). The function to be called is at *func.
  ** The arguments are on the stack, right after the function.
  ** When returns, all the results are on the stack, starting at the original
  ** function position.
  */ 
  void luaD_call (lua_State *L, StkId func, int nResults) {
    if (++L->nCcalls >= LUAI_MAXCCALLS) {
      if (L->nCcalls == LUAI_MAXCCALLS)
        luaG_runerror(L, "C stack overflow");
      else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
        luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
    }
    if (luaD_precall(L, func, nResults) == PCRLUA)  /* is a Lua function? */
      luaV_execute(L, 1);  /* call it */
    L->nCcalls--;
    luaC_checkGC(L);
  }
  
  
  static void resume (lua_State *L, void *ud) {
    StkId firstArg = cast(StkId, ud);
    CallInfo *ci = L->ci;
    if (L->status == 0) {  /* start coroutine? */
      lua_assert(ci == L->base_ci && firstArg > L->base);
      if (luaD_precall(L, firstArg - 1, LUA_MULTRET) != PCRLUA)
        return;
    }
    else {  /* resuming from previous yield */
      lua_assert(L->status == LUA_YIELD);
      L->status = 0;
      if (!f_isLua(ci)) {  /* `common' yield? */
        /* finish interrupted execution of `OP_CALL' */
        lua_assert(GET_OPCODE(*((ci-1)->savedpc - 1)) == OP_CALL ||
                   GET_OPCODE(*((ci-1)->savedpc - 1)) == OP_TAILCALL);
        if (luaD_poscall(L, firstArg))  /* complete it... */
          L->top = L->ci->top;  /* and correct top if not multiple results */
      }
      else  /* yielded inside a hook: just continue its execution */
        L->base = L->ci->base;
    }
    luaV_execute(L, cast_int(L->ci - L->base_ci));
  }
  
  
  static int resume_error (lua_State *L, const char *msg) {
    L->top = L->ci->base;
    setsvalue2s(L, L->top, luaS_new(L, msg));
    incr_top(L);
    lua_unlock(L);
    return LUA_ERRRUN;
  }
  
  
  LUA_API int lua_resume (lua_State *L, int nargs) {
    int status;
    lua_lock(L);
    if (L->status != LUA_YIELD && (L->status != 0 || L->ci != L->base_ci))
        return resume_error(L, "cannot resume non-suspended coroutine");
    if (L->nCcalls >= LUAI_MAXCCALLS)
      return resume_error(L, "C stack overflow");
    luai_userstateresume(L, nargs);
    lua_assert(L->errfunc == 0);
    L->baseCcalls = ++L->nCcalls;
    status = luaD_rawrunprotected(L, resume, L->top - nargs);
    if (status != 0) {  /* error? */
      L->status = cast_byte(status);  /* mark thread as `dead' */
      luaD_seterrorobj(L, status, L->top);
      L->ci->top = L->top;
    }
    else {
      lua_assert(L->nCcalls == L->baseCcalls);
      status = L->status;
    }
    --L->nCcalls;
    lua_unlock(L);
    return status;
  }
  
  
  LUA_API int lua_yield (lua_State *L, int nresults) {
    luai_userstateyield(L, nresults);
    lua_lock(L);
    if (L->nCcalls > L->baseCcalls)
      luaG_runerror(L, "attempt to yield across metamethod/C-call boundary");
    L->base = L->top - nresults;  /* protect stack slots below */
    L->status = LUA_YIELD;
    lua_unlock(L);
    return -1;
  }
  
  
  int luaD_pcall (lua_State *L, Pfunc func, void *u,
                  ptrdiff_t old_top, ptrdiff_t ef) {
    int status;
    unsigned short oldnCcalls = L->nCcalls;
    ptrdiff_t old_ci = saveci(L, L->ci);
    lu_byte old_allowhooks = L->allowhook;
    ptrdiff_t old_errfunc = L->errfunc;
    L->errfunc = ef;
    status = luaD_rawrunprotected(L, func, u);
    if (status != 0) {  /* an error occurred? */
      StkId oldtop = restorestack(L, old_top);
      luaF_close(L, oldtop);  /* close eventual pending closures */
      luaD_seterrorobj(L, status, oldtop);
      L->nCcalls = oldnCcalls;
      L->ci = restoreci(L, old_ci);
      L->base = L->ci->base;
      L->savedpc = L->ci->savedpc;
      L->allowhook = old_allowhooks;
      restore_stack_limit(L);
    }
    L->errfunc = old_errfunc;
    return status;
  }
  
  
  
  /*
  ** Execute a protected parser.
  */
  struct SParser {  /* data to `f_parser' */
    ZIO *z;
    Mbuffer buff;  /* buffer to be used by the scanner */
    const char *name;
  };
  
  static void f_parser (lua_State *L, void *ud) {
    int i;
    Proto *tf;
    Closure *cl;
    struct SParser *p = cast(struct SParser *, ud);
    int c = luaZ_lookahead(p->z);
    luaC_checkGC(L);
    tf = ((c == LUA_SIGNATURE[0]) ? luaU_undump : luaY_parser)(L, p->z,
                                                               &p->buff, p->name);
    cl = luaF_newLclosure(L, tf->nups, hvalue(gt(L)));
    cl->l.p = tf;
    for (i = 0; i < tf->nups; i++)  /* initialize eventual upvalues */
      cl->l.upvals[i] = luaF_newupval(L);
    setclvalue(L, L->top, cl);
    incr_top(L);
  }
  
  
  int luaD_protectedparser (lua_State *L, ZIO *z, const char *name) {
    struct SParser p;
    int status;
    p.z = z; p.name = name;
    luaZ_initbuffer(L, &p.buff);
    status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
    luaZ_freebuffer(L, &p.buff);
    return status;
  }
  
  
  