mudgangster

Tiny, scriptable MUD client
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ldebug.cc (20399B)

      1 /*
      2 ** $Id: ldebug.c,v 2.121.1.2 2017/07/10 17:21:50 roberto Exp $
      3 ** Debug Interface
      4 ** See Copyright Notice in lua.h
      5 */
      6 
      7 #define ldebug_c
      8 #define LUA_CORE
      9 
     10 #include "lprefix.h"
     11 
     12 
     13 #include <stdarg.h>
     14 #include <stddef.h>
     15 #include <string.h>
     16 
     17 #include "lua.h"
     18 
     19 #include "lapi.h"
     20 #include "lcode.h"
     21 #include "ldebug.h"
     22 #include "ldo.h"
     23 #include "lfunc.h"
     24 #include "lobject.h"
     25 #include "lopcodes.h"
     26 #include "lstate.h"
     27 #include "lstring.h"
     28 #include "ltable.h"
     29 #include "ltm.h"
     30 #include "lvm.h"
     31 
     32 
     33 
     34 #define noLuaClosure(f)		((f) == NULL || (f)->c.tt == LUA_TCCL)
     35 
     36 
     37 /* Active Lua function (given call info) */
     38 #define ci_func(ci)		(clLvalue((ci)->func))
     39 
     40 
     41 static const char *funcnamefromcode (lua_State *L, CallInfo *ci,
     42                                     const char **name);
     43 
     44 
     45 static int currentpc (CallInfo *ci) {
     46   lua_assert(isLua(ci));
     47   return pcRel(ci->u.l.savedpc, ci_func(ci)->p);
     48 }
     49 
     50 
     51 static int currentline (CallInfo *ci) {
     52   return getfuncline(ci_func(ci)->p, currentpc(ci));
     53 }
     54 
     55 
     56 /*
     57 ** If function yielded, its 'func' can be in the 'extra' field. The
     58 ** next function restores 'func' to its correct value for debugging
     59 ** purposes. (It exchanges 'func' and 'extra'; so, when called again,
     60 ** after debugging, it also "re-restores" ** 'func' to its altered value.
     61 */
     62 static void swapextra (lua_State *L) {
     63   if (L->status == LUA_YIELD) {
     64     CallInfo *ci = L->ci;  /* get function that yielded */
     65     StkId temp = ci->func;  /* exchange its 'func' and 'extra' values */
     66     ci->func = restorestack(L, ci->extra);
     67     ci->extra = savestack(L, temp);
     68   }
     69 }
     70 
     71 
     72 /*
     73 ** This function can be called asynchronously (e.g. during a signal).
     74 ** Fields 'oldpc', 'basehookcount', and 'hookcount' (set by
     75 ** 'resethookcount') are for debug only, and it is no problem if they
     76 ** get arbitrary values (causes at most one wrong hook call). 'hookmask'
     77 ** is an atomic value. We assume that pointers are atomic too (e.g., gcc
     78 ** ensures that for all platforms where it runs). Moreover, 'hook' is
     79 ** always checked before being called (see 'luaD_hook').
     80 */
     81 LUA_API void lua_sethook (lua_State *L, lua_Hook func, int mask, int count) {
     82   if (func == NULL || mask == 0) {  /* turn off hooks? */
     83     mask = 0;
     84     func = NULL;
     85   }
     86   if (isLua(L->ci))
     87     L->oldpc = L->ci->u.l.savedpc;
     88   L->hook = func;
     89   L->basehookcount = count;
     90   resethookcount(L);
     91   L->hookmask = cast_byte(mask);
     92 }
     93 
     94 
     95 LUA_API lua_Hook lua_gethook (lua_State *L) {
     96   return L->hook;
     97 }
     98 
     99 
    100 LUA_API int lua_gethookmask (lua_State *L) {
    101   return L->hookmask;
    102 }
    103 
    104 
    105 LUA_API int lua_gethookcount (lua_State *L) {
    106   return L->basehookcount;
    107 }
    108 
    109 
    110 LUA_API int lua_getstack (lua_State *L, int level, lua_Debug *ar) {
    111   int status;
    112   CallInfo *ci;
    113   if (level < 0) return 0;  /* invalid (negative) level */
    114   lua_lock(L);
    115   for (ci = L->ci; level > 0 && ci != &L->base_ci; ci = ci->previous)
    116     level--;
    117   if (level == 0 && ci != &L->base_ci) {  /* level found? */
    118     status = 1;
    119     ar->i_ci = ci;
    120   }
    121   else status = 0;  /* no such level */
    122   lua_unlock(L);
    123   return status;
    124 }
    125 
    126 
    127 static const char *upvalname (Proto *p, int uv) {
    128   TString *s = check_exp(uv < p->sizeupvalues, p->upvalues[uv].name);
    129   if (s == NULL) return "?";
    130   else return getstr(s);
    131 }
    132 
    133 
    134 static const char *findvararg (CallInfo *ci, int n, StkId *pos) {
    135   int nparams = clLvalue(ci->func)->p->numparams;
    136   if (n >= cast_int(ci->u.l.base - ci->func) - nparams)
    137     return NULL;  /* no such vararg */
    138   else {
    139     *pos = ci->func + nparams + n;
    140     return "(*vararg)";  /* generic name for any vararg */
    141   }
    142 }
    143 
    144 
    145 static const char *findlocal (lua_State *L, CallInfo *ci, int n,
    146                               StkId *pos) {
    147   const char *name = NULL;
    148   StkId base;
    149   if (isLua(ci)) {
    150     if (n < 0)  /* access to vararg values? */
    151       return findvararg(ci, -n, pos);
    152     else {
    153       base = ci->u.l.base;
    154       name = luaF_getlocalname(ci_func(ci)->p, n, currentpc(ci));
    155     }
    156   }
    157   else
    158     base = ci->func + 1;
    159   if (name == NULL) {  /* no 'standard' name? */
    160     StkId limit = (ci == L->ci) ? L->top : ci->next->func;
    161     if (limit - base >= n && n > 0)  /* is 'n' inside 'ci' stack? */
    162       name = "(*temporary)";  /* generic name for any valid slot */
    163     else
    164       return NULL;  /* no name */
    165   }
    166   *pos = base + (n - 1);
    167   return name;
    168 }
    169 
    170 
    171 LUA_API const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n) {
    172   const char *name;
    173   lua_lock(L);
    174   swapextra(L);
    175   if (ar == NULL) {  /* information about non-active function? */
    176     if (!isLfunction(L->top - 1))  /* not a Lua function? */
    177       name = NULL;
    178     else  /* consider live variables at function start (parameters) */
    179       name = luaF_getlocalname(clLvalue(L->top - 1)->p, n, 0);
    180   }
    181   else {  /* active function; get information through 'ar' */
    182     StkId pos = NULL;  /* to avoid warnings */
    183     name = findlocal(L, ar->i_ci, n, &pos);
    184     if (name) {
    185       setobj2s(L, L->top, pos);
    186       api_incr_top(L);
    187     }
    188   }
    189   swapextra(L);
    190   lua_unlock(L);
    191   return name;
    192 }
    193 
    194 
    195 LUA_API const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n) {
    196   StkId pos = NULL;  /* to avoid warnings */
    197   const char *name;
    198   lua_lock(L);
    199   swapextra(L);
    200   name = findlocal(L, ar->i_ci, n, &pos);
    201   if (name) {
    202     setobjs2s(L, pos, L->top - 1);
    203     L->top--;  /* pop value */
    204   }
    205   swapextra(L);
    206   lua_unlock(L);
    207   return name;
    208 }
    209 
    210 
    211 static void funcinfo (lua_Debug *ar, Closure *cl) {
    212   if (noLuaClosure(cl)) {
    213     ar->source = "=[C]";
    214     ar->linedefined = -1;
    215     ar->lastlinedefined = -1;
    216     ar->what = "C";
    217   }
    218   else {
    219     Proto *p = cl->l.p;
    220     ar->source = p->source ? getstr(p->source) : "=?";
    221     ar->linedefined = p->linedefined;
    222     ar->lastlinedefined = p->lastlinedefined;
    223     ar->what = (ar->linedefined == 0) ? "main" : "Lua";
    224   }
    225   luaO_chunkid(ar->short_src, ar->source, LUA_IDSIZE);
    226 }
    227 
    228 
    229 static void collectvalidlines (lua_State *L, Closure *f) {
    230   if (noLuaClosure(f)) {
    231     setnilvalue(L->top);
    232     api_incr_top(L);
    233   }
    234   else {
    235     int i;
    236     TValue v;
    237     int *lineinfo = f->l.p->lineinfo;
    238     Table *t = luaH_new(L);  /* new table to store active lines */
    239     sethvalue(L, L->top, t);  /* push it on stack */
    240     api_incr_top(L);
    241     setbvalue(&v, 1);  /* boolean 'true' to be the value of all indices */
    242     for (i = 0; i < f->l.p->sizelineinfo; i++)  /* for all lines with code */
    243       luaH_setint(L, t, lineinfo[i], &v);  /* table[line] = true */
    244   }
    245 }
    246 
    247 
    248 static const char *getfuncname (lua_State *L, CallInfo *ci, const char **name) {
    249   if (ci == NULL)  /* no 'ci'? */
    250     return NULL;  /* no info */
    251   else if (ci->callstatus & CIST_FIN) {  /* is this a finalizer? */
    252     *name = "__gc";
    253     return "metamethod";  /* report it as such */
    254   }
    255   /* calling function is a known Lua function? */
    256   else if (!(ci->callstatus & CIST_TAIL) && isLua(ci->previous))
    257     return funcnamefromcode(L, ci->previous, name);
    258   else return NULL;  /* no way to find a name */
    259 }
    260 
    261 
    262 static int auxgetinfo (lua_State *L, const char *what, lua_Debug *ar,
    263                        Closure *f, CallInfo *ci) {
    264   int status = 1;
    265   for (; *what; what++) {
    266     switch (*what) {
    267       case 'S': {
    268         funcinfo(ar, f);
    269         break;
    270       }
    271       case 'l': {
    272         ar->currentline = (ci && isLua(ci)) ? currentline(ci) : -1;
    273         break;
    274       }
    275       case 'u': {
    276         ar->nups = (f == NULL) ? 0 : f->c.nupvalues;
    277         if (noLuaClosure(f)) {
    278           ar->isvararg = 1;
    279           ar->nparams = 0;
    280         }
    281         else {
    282           ar->isvararg = f->l.p->is_vararg;
    283           ar->nparams = f->l.p->numparams;
    284         }
    285         break;
    286       }
    287       case 't': {
    288         ar->istailcall = (ci) ? ci->callstatus & CIST_TAIL : 0;
    289         break;
    290       }
    291       case 'n': {
    292         ar->namewhat = getfuncname(L, ci, &ar->name);
    293         if (ar->namewhat == NULL) {
    294           ar->namewhat = "";  /* not found */
    295           ar->name = NULL;
    296         }
    297         break;
    298       }
    299       case 'L':
    300       case 'f':  /* handled by lua_getinfo */
    301         break;
    302       default: status = 0;  /* invalid option */
    303     }
    304   }
    305   return status;
    306 }
    307 
    308 
    309 LUA_API int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar) {
    310   int status;
    311   Closure *cl;
    312   CallInfo *ci;
    313   StkId func;
    314   lua_lock(L);
    315   swapextra(L);
    316   if (*what == '>') {
    317     ci = NULL;
    318     func = L->top - 1;
    319     api_check(L, ttisfunction(func), "function expected");
    320     what++;  /* skip the '>' */
    321     L->top--;  /* pop function */
    322   }
    323   else {
    324     ci = ar->i_ci;
    325     func = ci->func;
    326     lua_assert(ttisfunction(ci->func));
    327   }
    328   cl = ttisclosure(func) ? clvalue(func) : NULL;
    329   status = auxgetinfo(L, what, ar, cl, ci);
    330   if (strchr(what, 'f')) {
    331     setobjs2s(L, L->top, func);
    332     api_incr_top(L);
    333   }
    334   swapextra(L);  /* correct before option 'L', which can raise a mem. error */
    335   if (strchr(what, 'L'))
    336     collectvalidlines(L, cl);
    337   lua_unlock(L);
    338   return status;
    339 }
    340 
    341 
    342 /*
    343 ** {======================================================
    344 ** Symbolic Execution
    345 ** =======================================================
    346 */
    347 
    348 static const char *getobjname (Proto *p, int lastpc, int reg,
    349                                const char **name);
    350 
    351 
    352 /*
    353 ** find a "name" for the RK value 'c'
    354 */
    355 static void kname (Proto *p, int pc, int c, const char **name) {
    356   if (ISK(c)) {  /* is 'c' a constant? */
    357     TValue *kvalue = &p->k[INDEXK(c)];
    358     if (ttisstring(kvalue)) {  /* literal constant? */
    359       *name = svalue(kvalue);  /* it is its own name */
    360       return;
    361     }
    362     /* else no reasonable name found */
    363   }
    364   else {  /* 'c' is a register */
    365     const char *what = getobjname(p, pc, c, name); /* search for 'c' */
    366     if (what && *what == 'c') {  /* found a constant name? */
    367       return;  /* 'name' already filled */
    368     }
    369     /* else no reasonable name found */
    370   }
    371   *name = "?";  /* no reasonable name found */
    372 }
    373 
    374 
    375 static int filterpc (int pc, int jmptarget) {
    376   if (pc < jmptarget)  /* is code conditional (inside a jump)? */
    377     return -1;  /* cannot know who sets that register */
    378   else return pc;  /* current position sets that register */
    379 }
    380 
    381 
    382 /*
    383 ** try to find last instruction before 'lastpc' that modified register 'reg'
    384 */
    385 static int findsetreg (Proto *p, int lastpc, int reg) {
    386   int pc;
    387   int setreg = -1;  /* keep last instruction that changed 'reg' */
    388   int jmptarget = 0;  /* any code before this address is conditional */
    389   for (pc = 0; pc < lastpc; pc++) {
    390     Instruction i = p->code[pc];
    391     OpCode op = GET_OPCODE(i);
    392     int a = GETARG_A(i);
    393     switch (op) {
    394       case OP_LOADNIL: {
    395         int b = GETARG_B(i);
    396         if (a <= reg && reg <= a + b)  /* set registers from 'a' to 'a+b' */
    397           setreg = filterpc(pc, jmptarget);
    398         break;
    399       }
    400       case OP_TFORCALL: {
    401         if (reg >= a + 2)  /* affect all regs above its base */
    402           setreg = filterpc(pc, jmptarget);
    403         break;
    404       }
    405       case OP_CALL:
    406       case OP_TAILCALL: {
    407         if (reg >= a)  /* affect all registers above base */
    408           setreg = filterpc(pc, jmptarget);
    409         break;
    410       }
    411       case OP_JMP: {
    412         int b = GETARG_sBx(i);
    413         int dest = pc + 1 + b;
    414         /* jump is forward and do not skip 'lastpc'? */
    415         if (pc < dest && dest <= lastpc) {
    416           if (dest > jmptarget)
    417             jmptarget = dest;  /* update 'jmptarget' */
    418         }
    419         break;
    420       }
    421       default:
    422         if (testAMode(op) && reg == a)  /* any instruction that set A */
    423           setreg = filterpc(pc, jmptarget);
    424         break;
    425     }
    426   }
    427   return setreg;
    428 }
    429 
    430 
    431 static const char *getobjname (Proto *p, int lastpc, int reg,
    432                                const char **name) {
    433   int pc;
    434   *name = luaF_getlocalname(p, reg + 1, lastpc);
    435   if (*name)  /* is a local? */
    436     return "local";
    437   /* else try symbolic execution */
    438   pc = findsetreg(p, lastpc, reg);
    439   if (pc != -1) {  /* could find instruction? */
    440     Instruction i = p->code[pc];
    441     OpCode op = GET_OPCODE(i);
    442     switch (op) {
    443       case OP_MOVE: {
    444         int b = GETARG_B(i);  /* move from 'b' to 'a' */
    445         if (b < GETARG_A(i))
    446           return getobjname(p, pc, b, name);  /* get name for 'b' */
    447         break;
    448       }
    449       case OP_GETTABUP:
    450       case OP_GETTABLE: {
    451         int k = GETARG_C(i);  /* key index */
    452         int t = GETARG_B(i);  /* table index */
    453         const char *vn = (op == OP_GETTABLE)  /* name of indexed variable */
    454                          ? luaF_getlocalname(p, t + 1, pc)
    455                          : upvalname(p, t);
    456         kname(p, pc, k, name);
    457         return (vn && strcmp(vn, LUA_ENV) == 0) ? "global" : "field";
    458       }
    459       case OP_GETUPVAL: {
    460         *name = upvalname(p, GETARG_B(i));
    461         return "upvalue";
    462       }
    463       case OP_LOADK:
    464       case OP_LOADKX: {
    465         int b = (op == OP_LOADK) ? GETARG_Bx(i)
    466                                  : GETARG_Ax(p->code[pc + 1]);
    467         if (ttisstring(&p->k[b])) {
    468           *name = svalue(&p->k[b]);
    469           return "constant";
    470         }
    471         break;
    472       }
    473       case OP_SELF: {
    474         int k = GETARG_C(i);  /* key index */
    475         kname(p, pc, k, name);
    476         return "method";
    477       }
    478       default: break;  /* go through to return NULL */
    479     }
    480   }
    481   return NULL;  /* could not find reasonable name */
    482 }
    483 
    484 
    485 /*
    486 ** Try to find a name for a function based on the code that called it.
    487 ** (Only works when function was called by a Lua function.)
    488 ** Returns what the name is (e.g., "for iterator", "method",
    489 ** "metamethod") and sets '*name' to point to the name.
    490 */
    491 static const char *funcnamefromcode (lua_State *L, CallInfo *ci,
    492                                      const char **name) {
    493   TMS tm = (TMS)0;  /* (initial value avoids warnings) */
    494   Proto *p = ci_func(ci)->p;  /* calling function */
    495   int pc = currentpc(ci);  /* calling instruction index */
    496   Instruction i = p->code[pc];  /* calling instruction */
    497   if (ci->callstatus & CIST_HOOKED) {  /* was it called inside a hook? */
    498     *name = "?";
    499     return "hook";
    500   }
    501   switch (GET_OPCODE(i)) {
    502     case OP_CALL:
    503     case OP_TAILCALL:
    504       return getobjname(p, pc, GETARG_A(i), name);  /* get function name */
    505     case OP_TFORCALL: {  /* for iterator */
    506       *name = "for iterator";
    507        return "for iterator";
    508     }
    509     /* other instructions can do calls through metamethods */
    510     case OP_SELF: case OP_GETTABUP: case OP_GETTABLE:
    511       tm = TM_INDEX;
    512       break;
    513     case OP_SETTABUP: case OP_SETTABLE:
    514       tm = TM_NEWINDEX;
    515       break;
    516     case OP_ADD: case OP_SUB: case OP_MUL: case OP_MOD:
    517     case OP_POW: case OP_DIV: case OP_IDIV: case OP_BAND:
    518     case OP_BOR: case OP_BXOR: case OP_SHL: case OP_SHR: {
    519       int offset = cast_int(GET_OPCODE(i)) - cast_int(OP_ADD);  /* ORDER OP */
    520       tm = cast(TMS, offset + cast_int(TM_ADD));  /* ORDER TM */
    521       break;
    522     }
    523     case OP_UNM: tm = TM_UNM; break;
    524     case OP_BNOT: tm = TM_BNOT; break;
    525     case OP_LEN: tm = TM_LEN; break;
    526     case OP_CONCAT: tm = TM_CONCAT; break;
    527     case OP_EQ: tm = TM_EQ; break;
    528     case OP_LT: tm = TM_LT; break;
    529     case OP_LE: tm = TM_LE; break;
    530     default:
    531       return NULL;  /* cannot find a reasonable name */
    532   }
    533   *name = getstr(G(L)->tmname[tm]);
    534   return "metamethod";
    535 }
    536 
    537 /* }====================================================== */
    538 
    539 
    540 
    541 /*
    542 ** The subtraction of two potentially unrelated pointers is
    543 ** not ISO C, but it should not crash a program; the subsequent
    544 ** checks are ISO C and ensure a correct result.
    545 */
    546 static int isinstack (CallInfo *ci, const TValue *o) {
    547   ptrdiff_t i = o - ci->u.l.base;
    548   return (0 <= i && i < (ci->top - ci->u.l.base) && ci->u.l.base + i == o);
    549 }
    550 
    551 
    552 /*
    553 ** Checks whether value 'o' came from an upvalue. (That can only happen
    554 ** with instructions OP_GETTABUP/OP_SETTABUP, which operate directly on
    555 ** upvalues.)
    556 */
    557 static const char *getupvalname (CallInfo *ci, const TValue *o,
    558                                  const char **name) {
    559   LClosure *c = ci_func(ci);
    560   int i;
    561   for (i = 0; i < c->nupvalues; i++) {
    562     if (c->upvals[i]->v == o) {
    563       *name = upvalname(c->p, i);
    564       return "upvalue";
    565     }
    566   }
    567   return NULL;
    568 }
    569 
    570 
    571 static const char *varinfo (lua_State *L, const TValue *o) {
    572   const char *name = NULL;  /* to avoid warnings */
    573   CallInfo *ci = L->ci;
    574   const char *kind = NULL;
    575   if (isLua(ci)) {
    576     kind = getupvalname(ci, o, &name);  /* check whether 'o' is an upvalue */
    577     if (!kind && isinstack(ci, o))  /* no? try a register */
    578       kind = getobjname(ci_func(ci)->p, currentpc(ci),
    579                         cast_int(o - ci->u.l.base), &name);
    580   }
    581   return (kind) ? luaO_pushfstring(L, " (%s '%s')", kind, name) : "";
    582 }
    583 
    584 
    585 l_noret luaG_typeerror (lua_State *L, const TValue *o, const char *op) {
    586   const char *t = luaT_objtypename(L, o);
    587   luaG_runerror(L, "attempt to %s a %s value%s", op, t, varinfo(L, o));
    588 }
    589 
    590 
    591 l_noret luaG_concaterror (lua_State *L, const TValue *p1, const TValue *p2) {
    592   if (ttisstring(p1) || cvt2str(p1)) p1 = p2;
    593   luaG_typeerror(L, p1, "concatenate");
    594 }
    595 
    596 
    597 l_noret luaG_opinterror (lua_State *L, const TValue *p1,
    598                          const TValue *p2, const char *msg) {
    599   lua_Number temp;
    600   if (!tonumber(p1, &temp))  /* first operand is wrong? */
    601     p2 = p1;  /* now second is wrong */
    602   luaG_typeerror(L, p2, msg);
    603 }
    604 
    605 
    606 /*
    607 ** Error when both values are convertible to numbers, but not to integers
    608 */
    609 l_noret luaG_tointerror (lua_State *L, const TValue *p1, const TValue *p2) {
    610   lua_Integer temp;
    611   if (!tointeger(p1, &temp))
    612     p2 = p1;
    613   luaG_runerror(L, "number%s has no integer representation", varinfo(L, p2));
    614 }
    615 
    616 
    617 l_noret luaG_ordererror (lua_State *L, const TValue *p1, const TValue *p2) {
    618   const char *t1 = luaT_objtypename(L, p1);
    619   const char *t2 = luaT_objtypename(L, p2);
    620   if (strcmp(t1, t2) == 0)
    621     luaG_runerror(L, "attempt to compare two %s values", t1);
    622   else
    623     luaG_runerror(L, "attempt to compare %s with %s", t1, t2);
    624 }
    625 
    626 
    627 /* add src:line information to 'msg' */
    628 const char *luaG_addinfo (lua_State *L, const char *msg, TString *src,
    629                                         int line) {
    630   char buff[LUA_IDSIZE];
    631   if (src)
    632     luaO_chunkid(buff, getstr(src), LUA_IDSIZE);
    633   else {  /* no source available; use "?" instead */
    634     buff[0] = '?'; buff[1] = '\0';
    635   }
    636   return luaO_pushfstring(L, "%s:%d: %s", buff, line, msg);
    637 }
    638 
    639 
    640 l_noret luaG_errormsg (lua_State *L) {
    641   if (L->errfunc != 0) {  /* is there an error handling function? */
    642     StkId errfunc = restorestack(L, L->errfunc);
    643     setobjs2s(L, L->top, L->top - 1);  /* move argument */
    644     setobjs2s(L, L->top - 1, errfunc);  /* push function */
    645     L->top++;  /* assume EXTRA_STACK */
    646     luaD_callnoyield(L, L->top - 2, 1);  /* call it */
    647   }
    648   luaD_throw(L, LUA_ERRRUN);
    649 }
    650 
    651 
    652 l_noret luaG_runerror (lua_State *L, const char *fmt, ...) {
    653   CallInfo *ci = L->ci;
    654   const char *msg;
    655   va_list argp;
    656   luaC_checkGC(L);  /* error message uses memory */
    657   va_start(argp, fmt);
    658   msg = luaO_pushvfstring(L, fmt, argp);  /* format message */
    659   va_end(argp);
    660   if (isLua(ci))  /* if Lua function, add source:line information */
    661     luaG_addinfo(L, msg, ci_func(ci)->p->source, currentline(ci));
    662   luaG_errormsg(L);
    663 }
    664 
    665 
    666 void luaG_traceexec (lua_State *L) {
    667   CallInfo *ci = L->ci;
    668   lu_byte mask = L->hookmask;
    669   int counthook = (--L->hookcount == 0 && (mask & LUA_MASKCOUNT));
    670   if (counthook)
    671     resethookcount(L);  /* reset count */
    672   else if (!(mask & LUA_MASKLINE))
    673     return;  /* no line hook and count != 0; nothing to be done */
    674   if (ci->callstatus & CIST_HOOKYIELD) {  /* called hook last time? */
    675     ci->callstatus &= ~CIST_HOOKYIELD;  /* erase mark */
    676     return;  /* do not call hook again (VM yielded, so it did not move) */
    677   }
    678   if (counthook)
    679     luaD_hook(L, LUA_HOOKCOUNT, -1);  /* call count hook */
    680   if (mask & LUA_MASKLINE) {
    681     Proto *p = ci_func(ci)->p;
    682     int npc = pcRel(ci->u.l.savedpc, p);
    683     int newline = getfuncline(p, npc);
    684     if (npc == 0 ||  /* call linehook when enter a new function, */
    685         ci->u.l.savedpc <= L->oldpc ||  /* when jump back (loop), or when */
    686         newline != getfuncline(p, pcRel(L->oldpc, p)))  /* enter a new line */
    687       luaD_hook(L, LUA_HOOKLINE, newline);  /* call line hook */
    688   }
    689   L->oldpc = ci->u.l.savedpc;
    690   if (L->status == LUA_YIELD) {  /* did hook yield? */
    691     if (counthook)
    692       L->hookcount = 1;  /* undo decrement to zero */
    693     ci->u.l.savedpc--;  /* undo increment (resume will increment it again) */
    694     ci->callstatus |= CIST_HOOKYIELD;  /* mark that it yielded */
    695     ci->func = L->top - 1;  /* protect stack below results */
    696     luaD_throw(L, LUA_YIELD);
    697   }
    698 }
    699