src/lj_err.c

   1 /*
   2 ** Error handling.
   3 ** Copyright (C) 2005-2012 Mike Pall. See Copyright Notice in luajit.h
   4 */
   5
   6 #define lj_err_c
   7 #define LUA_CORE
   8
   9 #include "lj_obj.h"
  10 #include "lj_err.h"
  11 #include "lj_debug.h"
  12 #include "lj_str.h"
  13 #include "lj_func.h"
  14 #include "lj_state.h"
  15 #include "lj_frame.h"
  16 #include "lj_ff.h"
  17 #include "lj_trace.h"
  18 #include "lj_vm.h"
  19
  20 /*
  21 ** LuaJIT can either use internal or external frame unwinding:
  22 **
  23 ** - Internal frame unwinding (INT) is free-standing and doesn't require
  24 **   any OS or library support.
  25 **
  26 ** - External frame unwinding (EXT) uses the system-provided unwind handler.
  27 **
  28 ** Pros and Cons:
  29 **
  30 ** - EXT requires unwind tables for *all* functions on the C stack between
  31 **   the pcall/catch and the error/throw. This is the default on x64,
  32 **   but needs to be manually enabled on x86/PPC for non-C++ code.
  33 **
  34 ** - INT is faster when actually throwing errors (but this happens rarely).
  35 **   Setting up error handlers is zero-cost in any case.
  36 **
  37 ** - EXT provides full interoperability with C++ exceptions. You can throw
  38 **   Lua errors or C++ exceptions through a mix of Lua frames and C++ frames.
  39 **   C++ destructors are called as needed. C++ exceptions caught by pcall
  40 **   are converted to the string "C++ exception". Lua errors can be caught
  41 **   with catch (...) in C++.
  42 **
  43 ** - INT has only limited support for automatically catching C++ exceptions
  44 **   on POSIX systems using DWARF2 stack unwinding. Other systems may use
  45 **   the wrapper function feature. Lua errors thrown through C++ frames
  46 **   cannot be caught by C++ code and C++ destructors are not run.
  47 **
  48 ** EXT is the default on x64 systems, INT is the default on all other systems.
  49 **
  50 ** EXT can be manually enabled on POSIX systems using GCC and DWARF2 stack
  51 ** unwinding with -DLUAJIT_UNWIND_EXTERNAL. *All* C code must be compiled
  52 ** with -funwind-tables (or -fexceptions). This includes LuaJIT itself (set
  53 ** TARGET_CFLAGS), all of your C/Lua binding code, all loadable C modules
  54 ** and all C libraries that have callbacks which may be used to call back
  55 ** into Lua. C++ code must *not* be compiled with -fno-exceptions.
  56 **
  57 ** EXT cannot be enabled on WIN32 since system exceptions use code-driven SEH.
  58 ** EXT is mandatory on WIN64 since the calling convention has an abundance
  59 ** of callee-saved registers (rbx, rbp, rsi, rdi, r12-r15, xmm6-xmm15).
  60 ** EXT is mandatory on POSIX/x64 since the interpreter doesn't save r12/r13.
  61 */
  62
  63 #if defined(__GNUC__) && (LJ_TARGET_X64 || defined(LUAJIT_UNWIND_EXTERNAL))
  64 #define LJ_UNWIND_EXT   1
  65 #elif LJ_TARGET_X64 && LJ_TARGET_WINDOWS
  66 #define LJ_UNWIND_EXT   1
  67 #endif
  68
  69 /* -- Error messages ------------------------------------------------------ */
  70
  71 /* Error message strings. */
  72 LJ_DATADEF const char *lj_err_allmsg =
  73 #define ERRDEF(name, msg)       msg "\0"
  74 #include "lj_errmsg.h"
  75 ;
  76
  77 /* -- Internal frame unwinding -------------------------------------------- */
  78
  79 /* Unwind Lua stack and move error message to new top. */
  80 LJ_NOINLINE static void unwindstack(lua_State *L, TValue *top)
  81 {
  82   lj_func_closeuv(L, top);
  83   if (top < L->top-1) {
  84     copyTV(L, top, L->top-1);
  85     L->top = top+1;
  86   }
  87   lj_state_relimitstack(L);
  88 }
  89
  90 /* Unwind until stop frame. Optionally cleanup frames. */
  91 static void *err_unwind(lua_State *L, void *stopcf, int errcode)
  92 {
  93   TValue *frame = L->base-1;
  94   void *cf = L->cframe;
  95   while (cf) {
  96     int32_t nres = cframe_nres(cframe_raw(cf));
  97     if (nres < 0) {  /* C frame without Lua frame? */
  98       TValue *top = restorestack(L, -nres);
  99       if (frame < top) {  /* Frame reached? */
 100         if (errcode) {
 101           L->cframe = cframe_prev(cf);
 102           L->base = frame+1;
 103           unwindstack(L, top);
 104         }
 105         return cf;
 106       }
 107     }
 108     if (frame <= tvref(L->stack))
 109       break;
 110     switch (frame_typep(frame)) {
 111     case FRAME_LUA:  /* Lua frame. */
 112     case FRAME_LUAP:
 113       frame = frame_prevl(frame);
 114       break;
 115     case FRAME_C:  /* C frame. */
 116 #if LJ_HASFFI
 117     unwind_c:
 118 #endif
 119 #if LJ_UNWIND_EXT
 120       if (errcode) {
 121         L->cframe = cframe_prev(cf);
 122         L->base = frame_prevd(frame) + 1;
 123         unwindstack(L, frame);
 124       } else if (cf != stopcf) {
 125         cf = cframe_prev(cf);
 126         frame = frame_prevd(frame);
 127         break;
 128       }
 129       return NULL;  /* Continue unwinding. */
 130 #else
 131       UNUSED(stopcf);
 132       cf = cframe_prev(cf);
 133       frame = frame_prevd(frame);
 134       break;
 135 #endif
 136     case FRAME_CP:  /* Protected C frame. */
 137       if (cframe_canyield(cf)) {  /* Resume? */
 138         if (errcode) {
 139           L->cframe = NULL;
 140           L->status = (uint8_t)errcode;
 141         }
 142         return cf;
 143       }
 144       if (errcode) {
 145         L->cframe = cframe_prev(cf);
 146         L->base = frame_prevd(frame) + 1;
 147         unwindstack(L, frame);
 148       }
 149       return cf;
 150     case FRAME_CONT:  /* Continuation frame. */
 151 #if LJ_HASFFI
 152       if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK)
 153         goto unwind_c;
 154 #endif
 155     case FRAME_VARG:  /* Vararg frame. */
 156       frame = frame_prevd(frame);
 157       break;
 158     case FRAME_PCALL:  /* FF pcall() frame. */
 159     case FRAME_PCALLH:  /* FF pcall() frame inside hook. */
 160       if (errcode) {
 161         if (errcode == LUA_YIELD) {
 162           frame = frame_prevd(frame);
 163           break;
 164         }
 165         if (frame_typep(frame) == FRAME_PCALL)
 166           hook_leave(G(L));
 167         L->cframe = cf;
 168         L->base = frame_prevd(frame) + 1;
 169         unwindstack(L, L->base);
 170       }
 171       return (void *)((intptr_t)cf | CFRAME_UNWIND_FF);
 172     }
 173   }
 174   /* No C frame. */
 175   if (errcode) {
 176     L->cframe = NULL;
 177     L->base = tvref(L->stack)+1;
 178     unwindstack(L, L->base);
 179     if (G(L)->panic)
 180       G(L)->panic(L);
 181     exit(EXIT_FAILURE);
 182   }
 183   return L;  /* Anything non-NULL will do. */
 184 }
 185
 186 /* -- External frame unwinding -------------------------------------------- */
 187
 188 #if defined(__GNUC__) && !defined(LUAJIT_NO_UNWIND)
 189
 190 /*
 191 ** We have to use our own definitions instead of the mandatory (!) unwind.h,
 192 ** since various OS, distros and compilers mess up the header installation.
 193 */
 194
 195 typedef struct _Unwind_Exception
 196 {
 197   uint64_t exclass;
 198   void (*excleanup)(int, struct _Unwind_Exception);
 199   uintptr_t p1, p2;
 200 } __attribute__((__aligned__)) _Unwind_Exception;
 201
 202 typedef struct _Unwind_Context _Unwind_Context;
 203
 204 #define _URC_OK                 0
 205 #define _URC_FATAL_PHASE1_ERROR 3
 206 #define _URC_HANDLER_FOUND      6
 207 #define _URC_INSTALL_CONTEXT    7
 208 #define _URC_CONTINUE_UNWIND    8
 209 #define _URC_FAILURE            9
 210
 211 #if !LJ_TARGET_ARM
 212
 213 extern uintptr_t _Unwind_GetCFA(_Unwind_Context *);
 214 extern void _Unwind_SetGR(_Unwind_Context *, int, uintptr_t);
 215 extern void _Unwind_SetIP(_Unwind_Context *, uintptr_t);
 216 extern void _Unwind_DeleteException(_Unwind_Exception *);
 217 extern int _Unwind_RaiseException(_Unwind_Exception *);
 218
 219 #define _UA_SEARCH_PHASE        1
 220 #define _UA_CLEANUP_PHASE       2
 221 #define _UA_HANDLER_FRAME       4
 222 #define _UA_FORCE_UNWIND        8
 223
 224 #define LJ_UEXCLASS             0x4c55414a49543200ULL   /* LUAJIT2\0 */
 225 #define LJ_UEXCLASS_MAKE(c)     (LJ_UEXCLASS | (uint64_t)(c))
 226 #define LJ_UEXCLASS_CHECK(cl)   (((cl) ^ LJ_UEXCLASS) <= 0xff)
 227 #define LJ_UEXCLASS_ERRCODE(cl) ((int)((cl) & 0xff))
 228
 229 /* DWARF2 personality handler referenced from interpreter .eh_frame. */
 230 LJ_FUNCA int lj_err_unwind_dwarf(int version, int actions,
 231   uint64_t uexclass, _Unwind_Exception *uex, _Unwind_Context *ctx)
 232 {
 233   void *cf;
 234   lua_State *L;
 235   if (version != 1)
 236     return _URC_FATAL_PHASE1_ERROR;
 237   UNUSED(uexclass);
 238   cf = (void *)_Unwind_GetCFA(ctx);
 239   L = cframe_L(cf);
 240   if ((actions & _UA_SEARCH_PHASE)) {
 241 #if LJ_UNWIND_EXT
 242     if (err_unwind(L, cf, 0) == NULL)
 243       return _URC_CONTINUE_UNWIND;
 244 #endif
 245     if (!LJ_UEXCLASS_CHECK(uexclass)) {
 246       setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
 247     }
 248     return _URC_HANDLER_FOUND;
 249   }
 250   if ((actions & _UA_CLEANUP_PHASE)) {
 251     int errcode;
 252     if (LJ_UEXCLASS_CHECK(uexclass)) {
 253       errcode = LJ_UEXCLASS_ERRCODE(uexclass);
 254     } else {
 255       if ((actions & _UA_HANDLER_FRAME))
 256         _Unwind_DeleteException(uex);
 257       errcode = LUA_ERRRUN;
 258     }
 259 #if LJ_UNWIND_EXT
 260     cf = err_unwind(L, cf, errcode);
 261     if ((actions & _UA_FORCE_UNWIND)) {
 262       return _URC_CONTINUE_UNWIND;
 263     } else if (cf) {
 264       _Unwind_SetGR(ctx, LJ_TARGET_EHRETREG, errcode);
 265       _Unwind_SetIP(ctx, (uintptr_t)(cframe_unwind_ff(cf) ?
 266                                      lj_vm_unwind_ff_eh :
 267                                      lj_vm_unwind_c_eh));
 268       return _URC_INSTALL_CONTEXT;
 269     }
 270 #if LJ_TARGET_X86ORX64
 271     else if ((actions & _UA_HANDLER_FRAME)) {
 272       /* Workaround for ancient libgcc bug. Still present in RHEL 5.5. :-/
 273       ** Real fix: http://gcc.gnu.org/viewcvs/trunk/gcc/unwind-dw2.c?r1=121165&r2=124837&pathrev=153877&diff_format=h
 274       */
 275       _Unwind_SetGR(ctx, LJ_TARGET_EHRETREG, errcode);
 276       _Unwind_SetIP(ctx, (uintptr_t)lj_vm_unwind_rethrow);
 277       return _URC_INSTALL_CONTEXT;
 278     }
 279 #endif
 280 #else
 281     /* This is not the proper way to escape from the unwinder. We get away with
 282     ** it on non-x64 because the interpreter restores all callee-saved regs.
 283     */
 284     lj_err_throw(L, errcode);
 285 #endif
 286   }
 287   return _URC_CONTINUE_UNWIND;
 288 }
 289
 290 #if LJ_UNWIND_EXT
 291 #if LJ_TARGET_OSX || defined(__OpenBSD__)
 292 /* Sorry, no thread safety for OSX. Complain to Apple, not me. */
 293 static _Unwind_Exception static_uex;
 294 #else
 295 static __thread _Unwind_Exception static_uex;
 296 #endif
 297
 298 /* Raise DWARF2 exception. */
 299 static void err_raise_ext(int errcode)
 300 {
 301   static_uex.exclass = LJ_UEXCLASS_MAKE(errcode);
 302   static_uex.excleanup = NULL;
 303   _Unwind_RaiseException(&static_uex);
 304 }
 305 #endif
 306
 307 #else
 308
 309 extern void _Unwind_DeleteException(void *);
 310 extern int __gnu_unwind_frame (void *, _Unwind_Context *);
 311 extern int _Unwind_VRS_Set(_Unwind_Context *, int, uint32_t, int, void *);
 312 extern int _Unwind_VRS_Get(_Unwind_Context *, int, uint32_t, int, void *);
 313
 314 static inline uint32_t _Unwind_GetGR(_Unwind_Context *ctx, int r)
 315 {
 316   uint32_t v;
 317   _Unwind_VRS_Get(ctx, 0, r, 0, &v);
 318   return v;
 319 }
 320
 321 static inline void _Unwind_SetGR(_Unwind_Context *ctx, int r, uint32_t v)
 322 {
 323   _Unwind_VRS_Set(ctx, 0, r, 0, &v);
 324 }
 325
 326 #define _US_VIRTUAL_UNWIND_FRAME        0
 327 #define _US_UNWIND_FRAME_STARTING       1
 328 #define _US_ACTION_MASK                 3
 329 #define _US_FORCE_UNWIND                8
 330
 331 /* ARM unwinder personality handler referenced from interpreter .ARM.extab. */
 332 LJ_FUNCA int lj_err_unwind_arm(int state, void *ucb, _Unwind_Context *ctx)
 333 {
 334   void *cf = (void *)_Unwind_GetGR(ctx, 13);
 335   lua_State *L = cframe_L(cf);
 336   if ((state & _US_ACTION_MASK) == _US_VIRTUAL_UNWIND_FRAME) {
 337     setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
 338     return _URC_HANDLER_FOUND;
 339   }
 340   if ((state&(_US_ACTION_MASK|_US_FORCE_UNWIND)) == _US_UNWIND_FRAME_STARTING) {
 341     _Unwind_DeleteException(ucb);
 342     _Unwind_SetGR(ctx, 15, (uint32_t)(void *)lj_err_throw);
 343     _Unwind_SetGR(ctx, 0, (uint32_t)L);
 344     _Unwind_SetGR(ctx, 1, (uint32_t)LUA_ERRRUN);
 345     return _URC_INSTALL_CONTEXT;
 346   }
 347   if (__gnu_unwind_frame(ucb, ctx) != _URC_OK)
 348     return _URC_FAILURE;
 349   return _URC_CONTINUE_UNWIND;
 350 }
 351
 352 #endif
 353
 354 #elif LJ_TARGET_X64 && LJ_TARGET_WINDOWS
 355
 356 /*
 357 ** Someone in Redmond owes me several days of my life. A lot of this is
 358 ** undocumented or just plain wrong on MSDN. Some of it can be gathered
 359 ** from 3rd party docs or must be found by trial-and-error. They really
 360 ** don't want you to write your own language-specific exception handler
 361 ** or to interact gracefully with MSVC. :-(
 362 **
 363 ** Apparently MSVC doesn't call C++ destructors for foreign exceptions
 364 ** unless you compile your C++ code with /EHa. Unfortunately this means
 365 ** catch (...) also catches things like access violations. The use of
 366 ** _set_se_translator doesn't really help, because it requires /EHa, too.
 367 */
 368
 369 #define WIN32_LEAN_AND_MEAN
 370 #include <windows.h>
 371
 372 /* Taken from: http://www.nynaeve.net/?p=99 */
 373 typedef struct UndocumentedDispatcherContext {
 374   ULONG64 ControlPc;
 375   ULONG64 ImageBase;
 376   PRUNTIME_FUNCTION FunctionEntry;
 377   ULONG64 EstablisherFrame;
 378   ULONG64 TargetIp;
 379   PCONTEXT ContextRecord;
 380   PEXCEPTION_ROUTINE LanguageHandler;
 381   PVOID HandlerData;
 382   PUNWIND_HISTORY_TABLE HistoryTable;
 383   ULONG ScopeIndex;
 384   ULONG Fill0;
 385 } UndocumentedDispatcherContext;
 386
 387 #ifdef _MSC_VER
 388 /* Another wild guess. */
 389 extern __DestructExceptionObject(EXCEPTION_RECORD *rec, int nothrow);
 390 #endif
 391
 392 #define LJ_MSVC_EXCODE          ((DWORD)0xe06d7363)
 393
 394 #define LJ_EXCODE               ((DWORD)0xe24c4a00)
 395 #define LJ_EXCODE_MAKE(c)       (LJ_EXCODE | (DWORD)(c))
 396 #define LJ_EXCODE_CHECK(cl)     (((cl) ^ LJ_EXCODE) <= 0xff)
 397 #define LJ_EXCODE_ERRCODE(cl)   ((int)((cl) & 0xff))
 398
 399 /* Win64 exception handler for interpreter frame. */
 400 LJ_FUNCA EXCEPTION_DISPOSITION lj_err_unwind_win64(EXCEPTION_RECORD *rec,
 401   void *cf, CONTEXT *ctx, UndocumentedDispatcherContext *dispatch)
 402 {
 403   lua_State *L = cframe_L(cf);
 404   int errcode = LJ_EXCODE_CHECK(rec->ExceptionCode) ?
 405                 LJ_EXCODE_ERRCODE(rec->ExceptionCode) : LUA_ERRRUN;
 406   if ((rec->ExceptionFlags & 6)) {  /* EH_UNWINDING|EH_EXIT_UNWIND */
 407     /* Unwind internal frames. */
 408     err_unwind(L, cf, errcode);
 409   } else {
 410     void *cf2 = err_unwind(L, cf, 0);
 411     if (cf2) {  /* We catch it, so start unwinding the upper frames. */
 412       if (rec->ExceptionCode == LJ_MSVC_EXCODE) {
 413 #ifdef _MSC_VER
 414         __DestructExceptionObject(rec, 1);
 415 #endif
 416         setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
 417       } else if (!LJ_EXCODE_CHECK(rec->ExceptionCode)) {
 418         /* Don't catch access violations etc. */
 419         return ExceptionContinueSearch;
 420       }
 421       /* Unwind the stack and call all handlers for all lower C frames
 422       ** (including ourselves) again with EH_UNWINDING set. Then set
 423       ** rsp = cf, rax = errcode and jump to the specified target.
 424       */
 425       RtlUnwindEx(cf, (void *)((cframe_unwind_ff(cf2) && errcode != LUA_YIELD) ?
 426                                lj_vm_unwind_ff_eh :
 427                                lj_vm_unwind_c_eh),
 428                   rec, (void *)errcode, ctx, dispatch->HistoryTable);
 429       /* RtlUnwindEx should never return. */
 430     }
 431   }
 432   return ExceptionContinueSearch;
 433 }
 434
 435 /* Raise Windows exception. */
 436 static void err_raise_ext(int errcode)
 437 {
 438   RaiseException(LJ_EXCODE_MAKE(errcode), 1 /* EH_NONCONTINUABLE */, 0, NULL);
 439 }
 440
 441 #endif
 442
 443 /* -- Error handling ------------------------------------------------------ */
 444
 445 /* Throw error. Find catch frame, unwind stack and continue. */
 446 LJ_NOINLINE void LJ_FASTCALL lj_err_throw(lua_State *L, int errcode)
 447 {
 448   global_State *g = G(L);
 449   lj_trace_abort(g);
 450   setgcrefnull(g->jit_L);
 451   L->status = 0;
 452 #if LJ_UNWIND_EXT
 453   err_raise_ext(errcode);
 454   /*
 455   ** A return from this function signals a corrupt C stack that cannot be
 456   ** unwound. We have no choice but to call the panic function and exit.
 457   **
 458   ** Usually this is caused by a C function without unwind information.
 459   ** This should never happen on x64, but may happen if you've manually
 460   ** enabled LUAJIT_UNWIND_EXTERNAL and forgot to recompile *every*
 461   ** non-C++ file with -funwind-tables.
 462   */
 463   if (G(L)->panic)
 464     G(L)->panic(L);
 465 #else
 466   {
 467     void *cf = err_unwind(L, NULL, errcode);
 468     if (cframe_unwind_ff(cf))
 469       lj_vm_unwind_ff(cframe_raw(cf));
 470     else
 471       lj_vm_unwind_c(cframe_raw(cf), errcode);
 472   }
 473 #endif
 474   exit(EXIT_FAILURE);
 475 }
 476
 477 /* Return string object for error message. */
 478 LJ_NOINLINE GCstr *lj_err_str(lua_State *L, ErrMsg em)
 479 {
 480   return lj_str_newz(L, err2msg(em));
 481 }
 482
 483 /* Out-of-memory error. */
 484 LJ_NOINLINE void lj_err_mem(lua_State *L)
 485 {
 486   if (L->status == LUA_ERRERR+1)  /* Don't touch the stack during lua_open. */
 487     lj_vm_unwind_c(L->cframe, LUA_ERRMEM);
 488   L->top = L->base;
 489   setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRMEM));
 490   lj_err_throw(L, LUA_ERRMEM);
 491 }
 492
 493 /* Find error function for runtime errors. Requires an extra stack traversal. */
 494 static ptrdiff_t finderrfunc(lua_State *L)
 495 {
 496   cTValue *frame = L->base-1, *bot = tvref(L->stack);
 497   void *cf = L->cframe;
 498   while (frame > bot) {
 499     lua_assert(cf != NULL);
 500     while (cframe_nres(cframe_raw(cf)) < 0) {  /* cframe without frame? */
 501       if (frame >= restorestack(L, -cframe_nres(cf)))
 502         break;
 503       if (cframe_errfunc(cf) >= 0)  /* Error handler not inherited (-1)? */
 504         return cframe_errfunc(cf);
 505       cf = cframe_prev(cf);  /* Else unwind cframe and continue searching. */
 506       if (cf == NULL)
 507         return 0;
 508     }
 509     switch (frame_typep(frame)) {
 510     case FRAME_LUA:
 511     case FRAME_LUAP:
 512       frame = frame_prevl(frame);
 513       break;
 514     case FRAME_C:
 515       cf = cframe_prev(cf);
 516       /* fallthrough */
 517     case FRAME_CONT:
 518 #if LJ_HASFFI
 519       if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK)
 520         cf = cframe_prev(cf);
 521 #endif
 522     case FRAME_VARG:
 523       frame = frame_prevd(frame);
 524       break;
 525     case FRAME_CP:
 526       if (cframe_canyield(cf)) return 0;
 527       if (cframe_errfunc(cf) >= 0)
 528         return cframe_errfunc(cf);
 529       frame = frame_prevd(frame);
 530       break;
 531     case FRAME_PCALL:
 532     case FRAME_PCALLH:
 533       if (frame_ftsz(frame) >= (ptrdiff_t)(2*sizeof(TValue)))  /* xpcall? */
 534         return savestack(L, frame-1);  /* Point to xpcall's errorfunc. */
 535       return 0;
 536     default:
 537       lua_assert(0);
 538       return 0;
 539     }
 540   }
 541   return 0;
 542 }
 543
 544 /* Runtime error. */
 545 LJ_NOINLINE void lj_err_run(lua_State *L)
 546 {
 547   ptrdiff_t ef = finderrfunc(L);
 548   if (ef) {
 549     TValue *errfunc = restorestack(L, ef);
 550     TValue *top = L->top;
 551     lj_trace_abort(G(L));
 552     if (!tvisfunc(errfunc) || L->status == LUA_ERRERR) {
 553       setstrV(L, top-1, lj_err_str(L, LJ_ERR_ERRERR));
 554       lj_err_throw(L, LUA_ERRERR);
 555     }
 556     L->status = LUA_ERRERR;
 557     copyTV(L, top, top-1);
 558     copyTV(L, top-1, errfunc);
 559     L->top = top+1;
 560     lj_vm_call(L, top, 1+1);  /* Stack: |errfunc|msg| -> |msg| */
 561   }
 562   lj_err_throw(L, LUA_ERRRUN);
 563 }
 564
 565 /* Formatted runtime error message. */
 566 LJ_NORET LJ_NOINLINE static void err_msgv(lua_State *L, ErrMsg em, ...)
 567 {
 568   const char *msg;
 569   va_list argp;
 570   va_start(argp, em);
 571   if (curr_funcisL(L)) L->top = curr_topL(L);
 572   msg = lj_str_pushvf(L, err2msg(em), argp);
 573   va_end(argp);
 574   lj_debug_addloc(L, msg, L->base-1, NULL);
 575   lj_err_run(L);
 576 }
 577
 578 /* Non-vararg variant for better calling conventions. */
 579 LJ_NOINLINE void lj_err_msg(lua_State *L, ErrMsg em)
 580 {
 581   err_msgv(L, em);
 582 }
 583
 584 /* Lexer error. */
 585 LJ_NOINLINE void lj_err_lex(lua_State *L, GCstr *src, const char *tok,
 586                             BCLine line, ErrMsg em, va_list argp)
 587 {
 588   char buff[LUA_IDSIZE];
 589   const char *msg;
 590   lj_debug_shortname(buff, src);
 591   msg = lj_str_pushvf(L, err2msg(em), argp);
 592   msg = lj_str_pushf(L, "%s:%d: %s", buff, line, msg);
 593   if (tok)
 594     lj_str_pushf(L, err2msg(LJ_ERR_XNEAR), msg, tok);
 595   lj_err_throw(L, LUA_ERRSYNTAX);
 596 }
 597
 598 /* Typecheck error for operands. */
 599 LJ_NOINLINE void lj_err_optype(lua_State *L, cTValue *o, ErrMsg opm)
 600 {
 601   const char *tname = typename(o);
 602   const char *opname = err2msg(opm);
 603   if (curr_funcisL(L)) {
 604     GCproto *pt = curr_proto(L);
 605     const BCIns *pc = cframe_Lpc(L) - 1;
 606     const char *oname = NULL;
 607     const char *kind = lj_debug_slotname(pt, pc, (BCReg)(o-L->base), &oname);
 608     if (kind)
 609       err_msgv(L, LJ_ERR_BADOPRT, opname, kind, oname, tname);
 610   }
 611   err_msgv(L, LJ_ERR_BADOPRV, opname, tname);
 612 }
 613
 614 /* Typecheck error for ordered comparisons. */
 615 LJ_NOINLINE void lj_err_comp(lua_State *L, cTValue *o1, cTValue *o2)
 616 {
 617   const char *t1 = typename(o1);
 618   const char *t2 = typename(o2);
 619   err_msgv(L, t1 == t2 ? LJ_ERR_BADCMPV : LJ_ERR_BADCMPT, t1, t2);
 620   /* This assumes the two "boolean" entries are commoned by the C compiler. */
 621 }
 622
 623 /* Typecheck error for __call. */
 624 LJ_NOINLINE void lj_err_optype_call(lua_State *L, TValue *o)
 625 {
 626   /* Gross hack if lua_[p]call or pcall/xpcall fail for a non-callable object:
 627   ** L->base still points to the caller. So add a dummy frame with L instead
 628   ** of a function. See lua_getstack().
 629   */
 630   const BCIns *pc = cframe_Lpc(L);
 631   if (((ptrdiff_t)pc & FRAME_TYPE) != FRAME_LUA) {
 632     const char *tname = typename(o);
 633     setframe_pc(o, pc);
 634     setframe_gc(o, obj2gco(L));
 635     L->top = L->base = o+1;
 636     err_msgv(L, LJ_ERR_BADCALL, tname);
 637   }
 638   lj_err_optype(L, o, LJ_ERR_OPCALL);
 639 }
 640
 641 /* Error in context of caller. */
 642 LJ_NOINLINE void lj_err_callermsg(lua_State *L, const char *msg)
 643 {
 644   TValue *frame = L->base-1;
 645   TValue *pframe = NULL;
 646   if (frame_islua(frame)) {
 647     pframe = frame_prevl(frame);
 648   } else if (frame_iscont(frame)) {
 649 #if LJ_HASFFI
 650     if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK) {
 651       pframe = frame;
 652       frame = NULL;
 653     } else
 654 #endif
 655     {
 656       pframe = frame_prevd(frame);
 657 #if LJ_HASFFI
 658       /* Remove frame for FFI metamethods. */
 659       if (frame_func(frame)->c.ffid >= FF_ffi_meta___index &&
 660           frame_func(frame)->c.ffid <= FF_ffi_meta___tostring) {
 661         L->base = pframe+1;
 662         L->top = frame;
 663       }
 664 #endif
 665     }
 666   }
 667   lj_debug_addloc(L, msg, pframe, frame);
 668   lj_err_run(L);
 669 }
 670
 671 /* Formatted error in context of caller. */
 672 LJ_NOINLINE void lj_err_callerv(lua_State *L, ErrMsg em, ...)
 673 {
 674   const char *msg;
 675   va_list argp;
 676   va_start(argp, em);
 677   msg = lj_str_pushvf(L, err2msg(em), argp);
 678   va_end(argp);
 679   lj_err_callermsg(L, msg);
 680 }
 681
 682 /* Error in context of caller. */
 683 LJ_NOINLINE void lj_err_caller(lua_State *L, ErrMsg em)
 684 {
 685   lj_err_callermsg(L, err2msg(em));
 686 }
 687
 688 /* Argument error message. */
 689 LJ_NORET LJ_NOINLINE static void err_argmsg(lua_State *L, int narg,
 690                                             const char *msg)
 691 {
 692   const char *fname = "?";
 693   const char *ftype = lj_debug_funcname(L, L->base - 1, &fname);
 694   if (narg < 0 && narg > LUA_REGISTRYINDEX)
 695     narg = (int)(L->top - L->base) + narg + 1;
 696   if (ftype && ftype[3] == 'h' && --narg == 0)  /* Check for "method". */
 697     msg = lj_str_pushf(L, err2msg(LJ_ERR_BADSELF), fname, msg);
 698   else
 699     msg = lj_str_pushf(L, err2msg(LJ_ERR_BADARG), narg, fname, msg);
 700   lj_err_callermsg(L, msg);
 701 }
 702
 703 /* Formatted argument error. */
 704 LJ_NOINLINE void lj_err_argv(lua_State *L, int narg, ErrMsg em, ...)
 705 {
 706   const char *msg;
 707   va_list argp;
 708   va_start(argp, em);
 709   msg = lj_str_pushvf(L, err2msg(em), argp);
 710   va_end(argp);
 711   err_argmsg(L, narg, msg);
 712 }
 713
 714 /* Argument error. */
 715 LJ_NOINLINE void lj_err_arg(lua_State *L, int narg, ErrMsg em)
 716 {
 717   err_argmsg(L, narg, err2msg(em));
 718 }
 719
 720 /* Typecheck error for arguments. */
 721 LJ_NOINLINE void lj_err_argtype(lua_State *L, int narg, const char *xname)
 722 {
 723   TValue *o = narg < 0 ? L->top + narg : L->base + narg-1;
 724   const char *tname = o < L->top ? typename(o) : lj_obj_typename[0];
 725   const char *msg = lj_str_pushf(L, err2msg(LJ_ERR_BADTYPE), xname, tname);
 726   err_argmsg(L, narg, msg);
 727 }
 728
 729 /* Typecheck error for arguments. */
 730 LJ_NOINLINE void lj_err_argt(lua_State *L, int narg, int tt)
 731 {
 732   lj_err_argtype(L, narg, lj_obj_typename[tt+1]);
 733 }
 734
 735 /* -- Public error handling API ------------------------------------------- */
 736
 737 LUA_API lua_CFunction lua_atpanic(lua_State *L, lua_CFunction panicf)
 738 {
 739   lua_CFunction old = G(L)->panic;
 740   G(L)->panic = panicf;
 741   return old;
 742 }
 743
 744 /* Forwarders for the public API (C calling convention and no LJ_NORET). */
 745 LUA_API int lua_error(lua_State *L)
 746 {
 747   lj_err_run(L);
 748   return 0;  /* unreachable */
 749 }
 750
 751 LUALIB_API int luaL_argerror(lua_State *L, int narg, const char *msg)
 752 {
 753   err_argmsg(L, narg, msg);
 754   return 0;  /* unreachable */
 755 }
 756
 757 LUALIB_API int luaL_typerror(lua_State *L, int narg, const char *xname)
 758 {
 759   lj_err_argtype(L, narg, xname);
 760   return 0;  /* unreachable */
 761 }
 762
 763 LUALIB_API void luaL_where(lua_State *L, int level)
 764 {
 765   int size;
 766   cTValue *frame = lj_debug_frame(L, level, &size);
 767   lj_debug_addloc(L, "", frame, size ? frame+size : NULL);
 768 }
 769
 770 LUALIB_API int luaL_error(lua_State *L, const char *fmt, ...)
 771 {
 772   const char *msg;
 773   va_list argp;
 774   va_start(argp, fmt);
 775   msg = lj_str_pushvf(L, fmt, argp);
 776   va_end(argp);
 777   lj_err_callermsg(L, msg);
 778   return 0;  /* unreachable */
 779 }
 780