src/lj_debug.c

   1 /*
   2 ** Debugging and introspection.
   3 ** Copyright (C) 2005-2023 Mike Pall. See Copyright Notice in luajit.h
   4 */
   5
   6 #define lj_debug_c
   7 #define LUA_CORE
   8
   9 #include "lj_obj.h"
  10 #include "lj_err.h"
  11 #include "lj_debug.h"
  12 #include "lj_buf.h"
  13 #include "lj_tab.h"
  14 #include "lj_state.h"
  15 #include "lj_frame.h"
  16 #include "lj_bc.h"
  17 #include "lj_strfmt.h"
  18 #if LJ_HASJIT
  19 #include "lj_jit.h"
  20 #endif
  21
  22 /* -- Frames -------------------------------------------------------------- */
  23
  24 /* Get frame corresponding to a level. */
  25 cTValue *lj_debug_frame(lua_State *L, int level, int *size)
  26 {
  27   cTValue *frame, *nextframe, *bot = tvref(L->stack)+LJ_FR2;
  28   /* Traverse frames backwards. */
  29   for (nextframe = frame = L->base-1; frame > bot; ) {
  30     if (frame_gc(frame) == obj2gco(L))
  31       level++;  /* Skip dummy frames. See lj_err_optype_call(). */
  32     if (level-- == 0) {
  33       *size = (int)(nextframe - frame);
  34       return frame;  /* Level found. */
  35     }
  36     nextframe = frame;
  37     if (frame_islua(frame)) {
  38       frame = frame_prevl(frame);
  39     } else {
  40       if (frame_isvarg(frame))
  41         level++;  /* Skip vararg pseudo-frame. */
  42       frame = frame_prevd(frame);
  43     }
  44   }
  45   *size = level;
  46   return NULL;  /* Level not found. */
  47 }
  48
  49 /* Invalid bytecode position. */
  50 #define NO_BCPOS        (~(BCPos)0)
  51
  52 /* Return bytecode position for function/frame or NO_BCPOS. */
  53 static BCPos debug_framepc(lua_State *L, GCfunc *fn, cTValue *nextframe)
  54 {
  55   const BCIns *ins;
  56   GCproto *pt;
  57   BCPos pos;
  58   lj_assertL(fn->c.gct == ~LJ_TFUNC || fn->c.gct == ~LJ_TTHREAD,
  59              "function or frame expected");
  60   if (!isluafunc(fn)) {  /* Cannot derive a PC for non-Lua functions. */
  61     return NO_BCPOS;
  62   } else if (nextframe == NULL) {  /* Lua function on top. */
  63     void *cf = cframe_raw(L->cframe);
  64     if (cf == NULL || (char *)cframe_pc(cf) == (char *)cframe_L(cf))
  65       return NO_BCPOS;
  66     ins = cframe_pc(cf);  /* Only happens during error/hook handling. */
  67   } else {
  68     if (frame_islua(nextframe)) {
  69       ins = frame_pc(nextframe);
  70     } else if (frame_iscont(nextframe)) {
  71       ins = frame_contpc(nextframe);
  72     } else {
  73       /* Lua function below errfunc/gc/hook: find cframe to get the PC. */
  74       void *cf = cframe_raw(L->cframe);
  75       TValue *f = L->base-1;
  76       for (;;) {
  77         if (cf == NULL)
  78           return NO_BCPOS;
  79         while (cframe_nres(cf) < 0) {
  80           if (f >= restorestack(L, -cframe_nres(cf)))
  81             break;
  82           cf = cframe_raw(cframe_prev(cf));
  83           if (cf == NULL)
  84             return NO_BCPOS;
  85         }
  86         if (f < nextframe)
  87           break;
  88         if (frame_islua(f)) {
  89           f = frame_prevl(f);
  90         } else {
  91           if (frame_isc(f) || (frame_iscont(f) && frame_iscont_fficb(f)))
  92             cf = cframe_raw(cframe_prev(cf));
  93           f = frame_prevd(f);
  94         }
  95       }
  96       ins = cframe_pc(cf);
  97       if (!ins) return NO_BCPOS;
  98     }
  99   }
 100   pt = funcproto(fn);
 101   pos = proto_bcpos(pt, ins) - 1;
 102 #if LJ_HASJIT
 103   if (pos > pt->sizebc) {  /* Undo the effects of lj_trace_exit for JLOOP. */
 104     if (bc_isret(bc_op(ins[-1]))) {
 105       GCtrace *T = (GCtrace *)((char *)(ins-1) - offsetof(GCtrace, startins));
 106       pos = proto_bcpos(pt, mref(T->startpc, const BCIns));
 107     } else {
 108       pos = NO_BCPOS;  /* Punt in case of stack overflow for stitched trace. */
 109     }
 110   }
 111 #endif
 112   return pos;
 113 }
 114
 115 /* -- Line numbers -------------------------------------------------------- */
 116
 117 /* Get line number for a bytecode position. */
 118 BCLine LJ_FASTCALL lj_debug_line(GCproto *pt, BCPos pc)
 119 {
 120   const void *lineinfo = proto_lineinfo(pt);
 121   if (pc <= pt->sizebc && lineinfo) {
 122     BCLine first = pt->firstline;
 123     if (pc == pt->sizebc) return first + pt->numline;
 124     if (pc-- == 0) return first;
 125     if (pt->numline < 256)
 126       return first + (BCLine)((const uint8_t *)lineinfo)[pc];
 127     else if (pt->numline < 65536)
 128       return first + (BCLine)((const uint16_t *)lineinfo)[pc];
 129     else
 130       return first + (BCLine)((const uint32_t *)lineinfo)[pc];
 131   }
 132   return 0;
 133 }
 134
 135 /* Get line number for function/frame. */
 136 static BCLine debug_frameline(lua_State *L, GCfunc *fn, cTValue *nextframe)
 137 {
 138   BCPos pc = debug_framepc(L, fn, nextframe);
 139   if (pc != NO_BCPOS) {
 140     GCproto *pt = funcproto(fn);
 141     lj_assertL(pc <= pt->sizebc, "PC out of range");
 142     return lj_debug_line(pt, pc);
 143   }
 144   return -1;
 145 }
 146
 147 /* -- Variable names ------------------------------------------------------ */
 148
 149 /* Get name of a local variable from slot number and PC. */
 150 static const char *debug_varname(const GCproto *pt, BCPos pc, BCReg slot)
 151 {
 152   const char *p = (const char *)proto_varinfo(pt);
 153   if (p) {
 154     BCPos lastpc = 0;
 155     for (;;) {
 156       const char *name = p;
 157       uint32_t vn = *(const uint8_t *)p;
 158       BCPos startpc, endpc;
 159       if (vn < VARNAME__MAX) {
 160         if (vn == VARNAME_END) break;  /* End of varinfo. */
 161       } else {
 162         do { p++; } while (*(const uint8_t *)p);  /* Skip over variable name. */
 163       }
 164       p++;
 165       lastpc = startpc = lastpc + lj_buf_ruleb128(&p);
 166       if (startpc > pc) break;
 167       endpc = startpc + lj_buf_ruleb128(&p);
 168       if (pc < endpc && slot-- == 0) {
 169         if (vn < VARNAME__MAX) {
 170 #define VARNAMESTR(name, str)   str "\0"
 171           name = VARNAMEDEF(VARNAMESTR);
 172 #undef VARNAMESTR
 173           if (--vn) while (*name++ || --vn) ;
 174         }
 175         return name;
 176       }
 177     }
 178   }
 179   return NULL;
 180 }
 181
 182 /* Get name of local variable from 1-based slot number and function/frame. */
 183 static TValue *debug_localname(lua_State *L, const lua_Debug *ar,
 184                                const char **name, BCReg slot1)
 185 {
 186   uint32_t offset = (uint32_t)ar->i_ci & 0xffff;
 187   uint32_t size = (uint32_t)ar->i_ci >> 16;
 188   TValue *frame = tvref(L->stack) + offset;
 189   TValue *nextframe = size ? frame + size : NULL;
 190   GCfunc *fn = frame_func(frame);
 191   BCPos pc = debug_framepc(L, fn, nextframe);
 192   if (!nextframe) nextframe = L->top+LJ_FR2;
 193   if ((int)slot1 < 0) {  /* Negative slot number is for varargs. */
 194     if (pc != NO_BCPOS) {
 195       GCproto *pt = funcproto(fn);
 196       if ((pt->flags & PROTO_VARARG)) {
 197         slot1 = pt->numparams + (BCReg)(-(int)slot1);
 198         if (frame_isvarg(frame)) {  /* Vararg frame has been set up? (pc!=0) */
 199           nextframe = frame;
 200           frame = frame_prevd(frame);
 201         }
 202         if (frame + slot1+LJ_FR2 < nextframe) {
 203           *name = "(*vararg)";
 204           return frame+slot1;
 205         }
 206       }
 207     }
 208     return NULL;
 209   }
 210   if (pc != NO_BCPOS &&
 211       (*name = debug_varname(funcproto(fn), pc, slot1-1)) != NULL)
 212     ;
 213   else if (slot1 > 0 && frame + slot1+LJ_FR2 < nextframe)
 214     *name = "(*temporary)";
 215   return frame+slot1;
 216 }
 217
 218 /* Get name of upvalue. */
 219 const char *lj_debug_uvname(GCproto *pt, uint32_t idx)
 220 {
 221   const uint8_t *p = proto_uvinfo(pt);
 222   lj_assertX(idx < pt->sizeuv, "bad upvalue index");
 223   if (!p) return "";
 224   if (idx) while (*p++ || --idx) ;
 225   return (const char *)p;
 226 }
 227
 228 /* Get name and value of upvalue. */
 229 const char *lj_debug_uvnamev(cTValue *o, uint32_t idx, TValue **tvp, GCobj **op)
 230 {
 231   if (tvisfunc(o)) {
 232     GCfunc *fn = funcV(o);
 233     if (isluafunc(fn)) {
 234       GCproto *pt = funcproto(fn);
 235       if (idx < pt->sizeuv) {
 236         GCobj *uvo = gcref(fn->l.uvptr[idx]);
 237         *tvp = uvval(&uvo->uv);
 238         *op = uvo;
 239         return lj_debug_uvname(pt, idx);
 240       }
 241     } else {
 242       if (idx < fn->c.nupvalues) {
 243         *tvp = &fn->c.upvalue[idx];
 244         *op = obj2gco(fn);
 245         return "";
 246       }
 247     }
 248   }
 249   return NULL;
 250 }
 251
 252 /* Deduce name of an object from slot number and PC. */
 253 const char *lj_debug_slotname(GCproto *pt, const BCIns *ip, BCReg slot,
 254                               const char **name)
 255 {
 256   const char *lname;
 257 restart:
 258   lname = debug_varname(pt, proto_bcpos(pt, ip), slot);
 259   if (lname != NULL) { *name = lname; return "local"; }
 260   while (--ip > proto_bc(pt)) {
 261     BCIns ins = *ip;
 262     BCOp op = bc_op(ins);
 263     BCReg ra = bc_a(ins);
 264     if (bcmode_a(op) == BCMbase) {
 265       if (slot >= ra && (op != BC_KNIL || slot <= bc_d(ins)))
 266         return NULL;
 267     } else if (bcmode_a(op) == BCMdst && ra == slot) {
 268       switch (bc_op(ins)) {
 269       case BC_MOV:
 270         if (ra == slot) { slot = bc_d(ins); goto restart; }
 271         break;
 272       case BC_GGET:
 273         *name = strdata(gco2str(proto_kgc(pt, ~(ptrdiff_t)bc_d(ins))));
 274         return "global";
 275       case BC_TGETS:
 276         *name = strdata(gco2str(proto_kgc(pt, ~(ptrdiff_t)bc_c(ins))));
 277         if (ip > proto_bc(pt)) {
 278           BCIns insp = ip[-1];
 279           if (bc_op(insp) == BC_MOV && bc_a(insp) == ra+1+LJ_FR2 &&
 280               bc_d(insp) == bc_b(ins))
 281             return "method";
 282         }
 283         return "field";
 284       case BC_UGET:
 285         *name = lj_debug_uvname(pt, bc_d(ins));
 286         return "upvalue";
 287       default:
 288         return NULL;
 289       }
 290     }
 291   }
 292   return NULL;
 293 }
 294
 295 /* Deduce function name from caller of a frame. */
 296 const char *lj_debug_funcname(lua_State *L, cTValue *frame, const char **name)
 297 {
 298   cTValue *pframe;
 299   GCfunc *fn;
 300   BCPos pc;
 301   if (frame <= tvref(L->stack)+LJ_FR2)
 302     return NULL;
 303   if (frame_isvarg(frame))
 304     frame = frame_prevd(frame);
 305   pframe = frame_prev(frame);
 306   fn = frame_func(pframe);
 307   pc = debug_framepc(L, fn, frame);
 308   if (pc != NO_BCPOS) {
 309     GCproto *pt = funcproto(fn);
 310     const BCIns *ip = &proto_bc(pt)[check_exp(pc < pt->sizebc, pc)];
 311     MMS mm = bcmode_mm(bc_op(*ip));
 312     if (mm == MM_call) {
 313       BCReg slot = bc_a(*ip);
 314       if (bc_op(*ip) == BC_ITERC) slot -= 3;
 315       return lj_debug_slotname(pt, ip, slot, name);
 316     } else if (mm != MM__MAX) {
 317       *name = strdata(mmname_str(G(L), mm));
 318       return "metamethod";
 319     }
 320   }
 321   return NULL;
 322 }
 323
 324 /* -- Source code locations ----------------------------------------------- */
 325
 326 /* Generate shortened source name. */
 327 void lj_debug_shortname(char *out, GCstr *str, BCLine line)
 328 {
 329   const char *src = strdata(str);
 330   if (*src == '=') {
 331     strncpy(out, src+1, LUA_IDSIZE);  /* Remove first char. */
 332     out[LUA_IDSIZE-1] = '\0';  /* Ensures null termination. */
 333   } else if (*src == '@') {  /* Output "source", or "...source". */
 334     size_t len = str->len-1;
 335     src++;  /* Skip the `@' */
 336     if (len >= LUA_IDSIZE) {
 337       src += len-(LUA_IDSIZE-4);  /* Get last part of file name. */
 338       *out++ = '.'; *out++ = '.'; *out++ = '.';
 339     }
 340     strcpy(out, src);
 341   } else {  /* Output [string "string"] or [builtin:name]. */
 342     size_t len;  /* Length, up to first control char. */
 343     for (len = 0; len < LUA_IDSIZE-12; len++)
 344       if (((const unsigned char *)src)[len] < ' ') break;
 345     strcpy(out, line == ~(BCLine)0 ? "[builtin:" : "[string \""); out += 9;
 346     if (src[len] != '\0') {  /* Must truncate? */
 347       if (len > LUA_IDSIZE-15) len = LUA_IDSIZE-15;
 348       strncpy(out, src, len); out += len;
 349       strcpy(out, "..."); out += 3;
 350     } else {
 351       strcpy(out, src); out += len;
 352     }
 353     strcpy(out, line == ~(BCLine)0 ? "]" : "\"]");
 354   }
 355 }
 356
 357 /* Add current location of a frame to error message. */
 358 void lj_debug_addloc(lua_State *L, const char *msg,
 359                      cTValue *frame, cTValue *nextframe)
 360 {
 361   if (frame) {
 362     GCfunc *fn = frame_func(frame);
 363     if (isluafunc(fn)) {
 364       BCLine line = debug_frameline(L, fn, nextframe);
 365       if (line >= 0) {
 366         GCproto *pt = funcproto(fn);
 367         char buf[LUA_IDSIZE];
 368         lj_debug_shortname(buf, proto_chunkname(pt), pt->firstline);
 369         lj_strfmt_pushf(L, "%s:%d: %s", buf, line, msg);
 370         return;
 371       }
 372     }
 373   }
 374   lj_strfmt_pushf(L, "%s", msg);
 375 }
 376
 377 /* Push location string for a bytecode position to Lua stack. */
 378 void lj_debug_pushloc(lua_State *L, GCproto *pt, BCPos pc)
 379 {
 380   GCstr *name = proto_chunkname(pt);
 381   const char *s = strdata(name);
 382   MSize i, len = name->len;
 383   BCLine line = lj_debug_line(pt, pc);
 384   if (pt->firstline == ~(BCLine)0) {
 385     lj_strfmt_pushf(L, "builtin:%s", s);
 386   } else if (*s == '@') {
 387     s++; len--;
 388     for (i = len; i > 0; i--)
 389       if (s[i] == '/' || s[i] == '\\') {
 390         s += i+1;
 391         break;
 392       }
 393     lj_strfmt_pushf(L, "%s:%d", s, line);
 394   } else if (len > 40) {
 395     lj_strfmt_pushf(L, "%p:%d", pt, line);
 396   } else if (*s == '=') {
 397     lj_strfmt_pushf(L, "%s:%d", s+1, line);
 398   } else {
 399     lj_strfmt_pushf(L, "\"%s\":%d", s, line);
 400   }
 401 }
 402
 403 /* -- Public debug API ---------------------------------------------------- */
 404
 405 /* lua_getupvalue() and lua_setupvalue() are in lj_api.c. */
 406
 407 LUA_API const char *lua_getlocal(lua_State *L, const lua_Debug *ar, int n)
 408 {
 409   const char *name = NULL;
 410   if (ar) {
 411     TValue *o = debug_localname(L, ar, &name, (BCReg)n);
 412     if (name) {
 413       copyTV(L, L->top, o);
 414       incr_top(L);
 415     }
 416   } else if (tvisfunc(L->top-1) && isluafunc(funcV(L->top-1))) {
 417     name = debug_varname(funcproto(funcV(L->top-1)), 0, (BCReg)n-1);
 418   }
 419   return name;
 420 }
 421
 422 LUA_API const char *lua_setlocal(lua_State *L, const lua_Debug *ar, int n)
 423 {
 424   const char *name = NULL;
 425   TValue *o = debug_localname(L, ar, &name, (BCReg)n);
 426   if (name)
 427     copyTV(L, o, L->top-1);
 428   L->top--;
 429   return name;
 430 }
 431
 432 int lj_debug_getinfo(lua_State *L, const char *what, lj_Debug *ar, int ext)
 433 {
 434   int opt_f = 0, opt_L = 0;
 435   TValue *frame = NULL;
 436   TValue *nextframe = NULL;
 437   GCfunc *fn;
 438   if (*what == '>') {
 439     TValue *func = L->top - 1;
 440     if (!tvisfunc(func)) return 0;
 441     fn = funcV(func);
 442     L->top--;
 443     what++;
 444   } else {
 445     uint32_t offset = (uint32_t)ar->i_ci & 0xffff;
 446     uint32_t size = (uint32_t)ar->i_ci >> 16;
 447     lj_assertL(offset != 0, "bad frame offset");
 448     frame = tvref(L->stack) + offset;
 449     if (size) nextframe = frame + size;
 450     lj_assertL(frame <= tvref(L->maxstack) &&
 451                (!nextframe || nextframe <= tvref(L->maxstack)),
 452                "broken frame chain");
 453     fn = frame_func(frame);
 454     lj_assertL(fn->c.gct == ~LJ_TFUNC, "bad frame function");
 455   }
 456   for (; *what; what++) {
 457     if (*what == 'S') {
 458       if (isluafunc(fn)) {
 459         GCproto *pt = funcproto(fn);
 460         BCLine firstline = pt->firstline;
 461         GCstr *name = proto_chunkname(pt);
 462         ar->source = strdata(name);
 463         lj_debug_shortname(ar->short_src, name, pt->firstline);
 464         ar->linedefined = (int)firstline;
 465         ar->lastlinedefined = (int)(firstline + pt->numline);
 466         ar->what = (firstline || !pt->numline) ? "Lua" : "main";
 467       } else {
 468         ar->source = "=[C]";
 469         ar->short_src[0] = '[';
 470         ar->short_src[1] = 'C';
 471         ar->short_src[2] = ']';
 472         ar->short_src[3] = '\0';
 473         ar->linedefined = -1;
 474         ar->lastlinedefined = -1;
 475         ar->what = "C";
 476       }
 477     } else if (*what == 'l') {
 478       ar->currentline = frame ? debug_frameline(L, fn, nextframe) : -1;
 479     } else if (*what == 'u') {
 480       ar->nups = fn->c.nupvalues;
 481       if (ext) {
 482         if (isluafunc(fn)) {
 483           GCproto *pt = funcproto(fn);
 484           ar->nparams = pt->numparams;
 485           ar->isvararg = !!(pt->flags & PROTO_VARARG);
 486         } else {
 487           ar->nparams = 0;
 488           ar->isvararg = 1;
 489         }
 490       }
 491     } else if (*what == 'n') {
 492       ar->namewhat = frame ? lj_debug_funcname(L, frame, &ar->name) : NULL;
 493       if (ar->namewhat == NULL) {
 494         ar->namewhat = "";
 495         ar->name = NULL;
 496       }
 497     } else if (*what == 'f') {
 498       opt_f = 1;
 499     } else if (*what == 'L') {
 500       opt_L = 1;
 501     } else {
 502       return 0;  /* Bad option. */
 503     }
 504   }
 505   if (opt_f) {
 506     setfuncV(L, L->top, fn);
 507     incr_top(L);
 508   }
 509   if (opt_L) {
 510     if (isluafunc(fn)) {
 511       GCtab *t = lj_tab_new(L, 0, 0);
 512       GCproto *pt = funcproto(fn);
 513       const void *lineinfo = proto_lineinfo(pt);
 514       if (lineinfo) {
 515         BCLine first = pt->firstline;
 516         int sz = pt->numline < 256 ? 1 : pt->numline < 65536 ? 2 : 4;
 517         MSize i, szl = pt->sizebc-1;
 518         for (i = 0; i < szl; i++) {
 519           BCLine line = first +
 520             (sz == 1 ? (BCLine)((const uint8_t *)lineinfo)[i] :
 521              sz == 2 ? (BCLine)((const uint16_t *)lineinfo)[i] :
 522              (BCLine)((const uint32_t *)lineinfo)[i]);
 523           setboolV(lj_tab_setint(L, t, line), 1);
 524         }
 525       }
 526       settabV(L, L->top, t);
 527     } else {
 528       setnilV(L->top);
 529     }
 530     incr_top(L);
 531   }
 532   return 1;  /* Ok. */
 533 }
 534
 535 LUA_API int lua_getinfo(lua_State *L, const char *what, lua_Debug *ar)
 536 {
 537   return lj_debug_getinfo(L, what, (lj_Debug *)ar, 0);
 538 }
 539
 540 LUA_API int lua_getstack(lua_State *L, int level, lua_Debug *ar)
 541 {
 542   int size;
 543   cTValue *frame = lj_debug_frame(L, level, &size);
 544   if (frame) {
 545     ar->i_ci = (size << 16) + (int)(frame - tvref(L->stack));
 546     return 1;
 547   } else {
 548     ar->i_ci = level - size;
 549     return 0;
 550   }
 551 }
 552
 553 #if LJ_HASPROFILE
 554 /* Put the chunkname into a buffer. */
 555 static int debug_putchunkname(SBuf *sb, GCproto *pt, int pathstrip)
 556 {
 557   GCstr *name = proto_chunkname(pt);
 558   const char *p = strdata(name);
 559   if (pt->firstline == ~(BCLine)0) {
 560     lj_buf_putmem(sb, "[builtin:", 9);
 561     lj_buf_putstr(sb, name);
 562     lj_buf_putb(sb, ']');
 563     return 0;
 564   }
 565   if (*p == '=' || *p == '@') {
 566     MSize len = name->len-1;
 567     p++;
 568     if (pathstrip) {
 569       int i;
 570       for (i = len-1; i >= 0; i--)
 571         if (p[i] == '/' || p[i] == '\\') {
 572           len -= i+1;
 573           p = p+i+1;
 574           break;
 575         }
 576     }
 577     lj_buf_putmem(sb, p, len);
 578   } else {
 579     lj_buf_putmem(sb, "[string]", 8);
 580   }
 581   return 1;
 582 }
 583
 584 /* Put a compact stack dump into a buffer. */
 585 void lj_debug_dumpstack(lua_State *L, SBuf *sb, const char *fmt, int depth)
 586 {
 587   int level = 0, dir = 1, pathstrip = 1;
 588   MSize lastlen = 0;
 589   if (depth < 0) { level = ~depth; depth = dir = -1; }  /* Reverse frames. */
 590   while (level != depth) {  /* Loop through all frame. */
 591     int size;
 592     cTValue *frame = lj_debug_frame(L, level, &size);
 593     if (frame) {
 594       cTValue *nextframe = size ? frame+size : NULL;
 595       GCfunc *fn = frame_func(frame);
 596       const uint8_t *p = (const uint8_t *)fmt;
 597       int c;
 598       while ((c = *p++)) {
 599         switch (c) {
 600         case 'p':  /* Preserve full path. */
 601           pathstrip = 0;
 602           break;
 603         case 'F': case 'f': {  /* Dump function name. */
 604           const char *name;
 605           const char *what = lj_debug_funcname(L, frame, &name);
 606           if (what) {
 607             if (c == 'F' && isluafunc(fn)) {  /* Dump module:name for 'F'. */
 608               GCproto *pt = funcproto(fn);
 609               if (pt->firstline != ~(BCLine)0) {  /* Not a bytecode builtin. */
 610                 debug_putchunkname(sb, pt, pathstrip);
 611                 lj_buf_putb(sb, ':');
 612               }
 613             }
 614             lj_buf_putmem(sb, name, (MSize)strlen(name));
 615             break;
 616           }  /* else: can't derive a name, dump module:line. */
 617           }
 618           /* fallthrough */
 619         case 'l':  /* Dump module:line. */
 620           if (isluafunc(fn)) {
 621             GCproto *pt = funcproto(fn);
 622             if (debug_putchunkname(sb, pt, pathstrip)) {
 623               /* Regular Lua function. */
 624               BCLine line = c == 'l' ? debug_frameline(L, fn, nextframe) :
 625                                        pt->firstline;
 626               lj_buf_putb(sb, ':');
 627               lj_strfmt_putint(sb, line >= 0 ? line : pt->firstline);
 628             }
 629           } else if (isffunc(fn)) {  /* Dump numbered builtins. */
 630             lj_buf_putmem(sb, "[builtin#", 9);
 631             lj_strfmt_putint(sb, fn->c.ffid);
 632             lj_buf_putb(sb, ']');
 633           } else {  /* Dump C function address. */
 634             lj_buf_putb(sb, '@');
 635             lj_strfmt_putptr(sb, fn->c.f);
 636           }
 637           break;
 638         case 'Z':  /* Zap trailing separator. */
 639           lastlen = sbuflen(sb);
 640           break;
 641         default:
 642           lj_buf_putb(sb, c);
 643           break;
 644         }
 645       }
 646     } else if (dir == 1) {
 647       break;
 648     } else {
 649       level -= size;  /* Reverse frame order: quickly skip missing level. */
 650     }
 651     level += dir;
 652   }
 653   if (lastlen)
 654     sb->w = sb->b + lastlen;  /* Zap trailing separator. */
 655 }
 656 #endif
 657
 658 /* Number of frames for the leading and trailing part of a traceback. */
 659 #define TRACEBACK_LEVELS1       12
 660 #define TRACEBACK_LEVELS2       10
 661
 662 LUALIB_API void luaL_traceback (lua_State *L, lua_State *L1, const char *msg,
 663                                 int level)
 664 {
 665   int top = (int)(L->top - L->base);
 666   int lim = TRACEBACK_LEVELS1;
 667   lua_Debug ar;
 668   if (msg) lua_pushfstring(L, "%s\n", msg);
 669   lua_pushliteral(L, "stack traceback:");
 670   while (lua_getstack(L1, level++, &ar)) {
 671     GCfunc *fn;
 672     if (level > lim) {
 673       if (!lua_getstack(L1, level + TRACEBACK_LEVELS2, &ar)) {
 674         level--;
 675       } else {
 676         lua_pushliteral(L, "\n\t...");
 677         lua_getstack(L1, -10, &ar);
 678         level = ar.i_ci - TRACEBACK_LEVELS2;
 679       }
 680       lim = 2147483647;
 681       continue;
 682     }
 683     lua_getinfo(L1, "Snlf", &ar);
 684     fn = funcV(L1->top-1); L1->top--;
 685     if (isffunc(fn) && !*ar.namewhat)
 686       lua_pushfstring(L, "\n\t[builtin#%d]:", fn->c.ffid);
 687     else
 688       lua_pushfstring(L, "\n\t%s:", ar.short_src);
 689     if (ar.currentline > 0)
 690       lua_pushfstring(L, "%d:", ar.currentline);
 691     if (*ar.namewhat) {
 692       lua_pushfstring(L, " in function " LUA_QS, ar.name);
 693     } else {
 694       if (*ar.what == 'm') {
 695         lua_pushliteral(L, " in main chunk");
 696       } else if (*ar.what == 'C') {
 697         lua_pushfstring(L, " at %p", fn->c.f);
 698       } else {
 699         lua_pushfstring(L, " in function <%s:%d>",
 700                         ar.short_src, ar.linedefined);
 701       }
 702     }
 703     if ((int)(L->top - L->base) - top >= 15)
 704       lua_concat(L, (int)(L->top - L->base) - top);
 705   }
 706   lua_concat(L, (int)(L->top - L->base) - top);
 707 }
 708