src/lj_err.c

   1 /*
   2 ** Error handling.
   3 ** Copyright (C) 2005-2023 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 ** The POSIX/x64 interpreter only saves r12/r13 for INT (e.g. PS4).
  61 */
  62
  63 #if defined(__GNUC__) && (LJ_TARGET_X64 || defined(LUAJIT_UNWIND_EXTERNAL)) && !LJ_NO_UNWIND
  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           hook_leave(G(L));  /* Assumes nobody uses coroutines inside hooks. */
 140           L->cframe = NULL;
 141           L->status = (uint8_t)errcode;
 142         }
 143         return cf;
 144       }
 145       if (errcode) {
 146         L->cframe = cframe_prev(cf);
 147         L->base = frame_prevd(frame) + 1;
 148         unwindstack(L, frame);
 149       }
 150       return cf;
 151     case FRAME_CONT:  /* Continuation frame. */
 152 #if LJ_HASFFI
 153       if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK)
 154         goto unwind_c;
 155 #endif
 156       /* fallthrough */
 157     case FRAME_VARG:  /* Vararg frame. */
 158       frame = frame_prevd(frame);
 159       break;
 160     case FRAME_PCALL:  /* FF pcall() frame. */
 161     case FRAME_PCALLH:  /* FF pcall() frame inside hook. */
 162       if (errcode) {
 163         if (errcode == LUA_YIELD) {
 164           frame = frame_prevd(frame);
 165           break;
 166         }
 167         if (frame_typep(frame) == FRAME_PCALL)
 168           hook_leave(G(L));
 169         L->cframe = cf;
 170         L->base = frame_prevd(frame) + 1;
 171         unwindstack(L, L->base);
 172       }
 173       return (void *)((intptr_t)cf | CFRAME_UNWIND_FF);
 174     }
 175   }
 176   /* No C frame. */
 177   if (errcode) {
 178     L->cframe = NULL;
 179     L->base = tvref(L->stack)+1;
 180     unwindstack(L, L->base);
 181     if (G(L)->panic)
 182       G(L)->panic(L);
 183     exit(EXIT_FAILURE);
 184   }
 185   return L;  /* Anything non-NULL will do. */
 186 }
 187
 188 /* -- External frame unwinding -------------------------------------------- */
 189
 190 #if defined(__GNUC__) && !LJ_NO_UNWIND && !LJ_ABI_WIN
 191
 192 /*
 193 ** We have to use our own definitions instead of the mandatory (!) unwind.h,
 194 ** since various OS, distros and compilers mess up the header installation.
 195 */
 196
 197 typedef struct _Unwind_Exception
 198 {
 199   uint64_t exclass;
 200   void (*excleanup)(int, struct _Unwind_Exception *);
 201   uintptr_t p1, p2;
 202 } __attribute__((__aligned__)) _Unwind_Exception;
 203
 204 typedef struct _Unwind_Context _Unwind_Context;
 205
 206 #define _URC_OK                 0
 207 #define _URC_FATAL_PHASE1_ERROR 3
 208 #define _URC_HANDLER_FOUND      6
 209 #define _URC_INSTALL_CONTEXT    7
 210 #define _URC_CONTINUE_UNWIND    8
 211 #define _URC_FAILURE            9
 212
 213 #if !LJ_TARGET_ARM
 214
 215 extern uintptr_t _Unwind_GetCFA(_Unwind_Context *);
 216 extern void _Unwind_SetGR(_Unwind_Context *, int, uintptr_t);
 217 extern void _Unwind_SetIP(_Unwind_Context *, uintptr_t);
 218 extern void _Unwind_DeleteException(_Unwind_Exception *);
 219 extern int _Unwind_RaiseException(_Unwind_Exception *);
 220
 221 #define _UA_SEARCH_PHASE        1
 222 #define _UA_CLEANUP_PHASE       2
 223 #define _UA_HANDLER_FRAME       4
 224 #define _UA_FORCE_UNWIND        8
 225
 226 #define LJ_UEXCLASS             0x4c55414a49543200ULL   /* LUAJIT2\0 */
 227 #define LJ_UEXCLASS_MAKE(c)     (LJ_UEXCLASS | (uint64_t)(c))
 228 #define LJ_UEXCLASS_CHECK(cl)   (((cl) ^ LJ_UEXCLASS) <= 0xff)
 229 #define LJ_UEXCLASS_ERRCODE(cl) ((int)((cl) & 0xff))
 230
 231 /* DWARF2 personality handler referenced from interpreter .eh_frame. */
 232 LJ_FUNCA int lj_err_unwind_dwarf(int version, int actions,
 233   uint64_t uexclass, _Unwind_Exception *uex, _Unwind_Context *ctx)
 234 {
 235   void *cf;
 236   lua_State *L;
 237   if (version != 1)
 238     return _URC_FATAL_PHASE1_ERROR;
 239   UNUSED(uexclass);
 240   cf = (void *)_Unwind_GetCFA(ctx);
 241   L = cframe_L(cf);
 242   if ((actions & _UA_SEARCH_PHASE)) {
 243 #if LJ_UNWIND_EXT
 244     if (err_unwind(L, cf, 0) == NULL)
 245       return _URC_CONTINUE_UNWIND;
 246 #endif
 247     if (!LJ_UEXCLASS_CHECK(uexclass)) {
 248       setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
 249     }
 250     return _URC_HANDLER_FOUND;
 251   }
 252   if ((actions & _UA_CLEANUP_PHASE)) {
 253     int errcode;
 254     if (LJ_UEXCLASS_CHECK(uexclass)) {
 255       errcode = LJ_UEXCLASS_ERRCODE(uexclass);
 256     } else {
 257       if ((actions & _UA_HANDLER_FRAME))
 258         _Unwind_DeleteException(uex);
 259       errcode = LUA_ERRRUN;
 260     }
 261 #if LJ_UNWIND_EXT
 262     cf = err_unwind(L, cf, errcode);
 263     if ((actions & _UA_FORCE_UNWIND)) {
 264       return _URC_CONTINUE_UNWIND;
 265     } else if (cf) {
 266       _Unwind_SetGR(ctx, LJ_TARGET_EHRETREG, errcode);
 267       _Unwind_SetIP(ctx, (uintptr_t)(cframe_unwind_ff(cf) ?
 268                                      lj_vm_unwind_ff_eh :
 269                                      lj_vm_unwind_c_eh));
 270       return _URC_INSTALL_CONTEXT;
 271     }
 272 #if LJ_TARGET_X86ORX64
 273     else if ((actions & _UA_HANDLER_FRAME)) {
 274       /* Workaround for ancient libgcc bug. Still present in RHEL 5.5. :-/
 275       ** Real fix: http://gcc.gnu.org/viewcvs/trunk/gcc/unwind-dw2.c?r1=121165&r2=124837&pathrev=153877&diff_format=h
 276       */
 277       _Unwind_SetGR(ctx, LJ_TARGET_EHRETREG, errcode);
 278       _Unwind_SetIP(ctx, (uintptr_t)lj_vm_unwind_rethrow);
 279       return _URC_INSTALL_CONTEXT;
 280     }
 281 #endif
 282 #else
 283     /* This is not the proper way to escape from the unwinder. We get away with
 284     ** it on non-x64 because the interpreter restores all callee-saved regs.
 285     */
 286     lj_err_throw(L, errcode);
 287 #endif
 288   }
 289   return _URC_CONTINUE_UNWIND;
 290 }
 291
 292 #if LJ_UNWIND_EXT
 293 static __thread _Unwind_Exception static_uex;
 294
 295 /* Raise DWARF2 exception. */
 296 static void err_raise_ext(int errcode)
 297 {
 298   static_uex.exclass = LJ_UEXCLASS_MAKE(errcode);
 299   static_uex.excleanup = NULL;
 300   _Unwind_RaiseException(&static_uex);
 301 }
 302 #endif
 303
 304 #else
 305
 306 extern void _Unwind_DeleteException(void *);
 307 extern int __gnu_unwind_frame (void *, _Unwind_Context *);
 308 extern int _Unwind_VRS_Set(_Unwind_Context *, int, uint32_t, int, void *);
 309 extern int _Unwind_VRS_Get(_Unwind_Context *, int, uint32_t, int, void *);
 310
 311 static inline uint32_t _Unwind_GetGR(_Unwind_Context *ctx, int r)
 312 {
 313   uint32_t v;
 314   _Unwind_VRS_Get(ctx, 0, r, 0, &v);
 315   return v;
 316 }
 317
 318 static inline void _Unwind_SetGR(_Unwind_Context *ctx, int r, uint32_t v)
 319 {
 320   _Unwind_VRS_Set(ctx, 0, r, 0, &v);
 321 }
 322
 323 #define _US_VIRTUAL_UNWIND_FRAME        0
 324 #define _US_UNWIND_FRAME_STARTING       1
 325 #define _US_ACTION_MASK                 3
 326 #define _US_FORCE_UNWIND                8
 327
 328 /* ARM unwinder personality handler referenced from interpreter .ARM.extab. */
 329 LJ_FUNCA int lj_err_unwind_arm(int state, void *ucb, _Unwind_Context *ctx)
 330 {
 331   void *cf = (void *)_Unwind_GetGR(ctx, 13);
 332   lua_State *L = cframe_L(cf);
 333   if ((state & _US_ACTION_MASK) == _US_VIRTUAL_UNWIND_FRAME) {
 334     setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
 335     return _URC_HANDLER_FOUND;
 336   }
 337   if ((state&(_US_ACTION_MASK|_US_FORCE_UNWIND)) == _US_UNWIND_FRAME_STARTING) {
 338     _Unwind_DeleteException(ucb);
 339     _Unwind_SetGR(ctx, 15, (uint32_t)(void *)lj_err_throw);
 340     _Unwind_SetGR(ctx, 0, (uint32_t)L);
 341     _Unwind_SetGR(ctx, 1, (uint32_t)LUA_ERRRUN);
 342     return _URC_INSTALL_CONTEXT;
 343   }
 344   if (__gnu_unwind_frame(ucb, ctx) != _URC_OK)
 345     return _URC_FAILURE;
 346   return _URC_CONTINUE_UNWIND;
 347 }
 348
 349 #endif
 350
 351 #elif LJ_TARGET_X64 && LJ_ABI_WIN
 352
 353 /*
 354 ** Someone in Redmond owes me several days of my life. A lot of this is
 355 ** undocumented or just plain wrong on MSDN. Some of it can be gathered
 356 ** from 3rd party docs or must be found by trial-and-error. They really
 357 ** don't want you to write your own language-specific exception handler
 358 ** or to interact gracefully with MSVC. :-(
 359 **
 360 ** Apparently MSVC doesn't call C++ destructors for foreign exceptions
 361 ** unless you compile your C++ code with /EHa. Unfortunately this means
 362 ** catch (...) also catches things like access violations. The use of
 363 ** _set_se_translator doesn't really help, because it requires /EHa, too.
 364 */
 365
 366 #define WIN32_LEAN_AND_MEAN
 367 #include <windows.h>
 368
 369 /* Taken from: http://www.nynaeve.net/?p=99 */
 370 typedef struct UndocumentedDispatcherContext {
 371   ULONG64 ControlPc;
 372   ULONG64 ImageBase;
 373   PRUNTIME_FUNCTION FunctionEntry;
 374   ULONG64 EstablisherFrame;
 375   ULONG64 TargetIp;
 376   PCONTEXT ContextRecord;
 377   void (*LanguageHandler)(void);
 378   PVOID HandlerData;
 379   PUNWIND_HISTORY_TABLE HistoryTable;
 380   ULONG ScopeIndex;
 381   ULONG Fill0;
 382 } UndocumentedDispatcherContext;
 383
 384 /* Another wild guess. */
 385 extern void __DestructExceptionObject(EXCEPTION_RECORD *rec, int nothrow);
 386
 387 #ifdef MINGW_SDK_INIT
 388 /* Workaround for broken MinGW64 declaration. */
 389 VOID RtlUnwindEx_FIXED(PVOID,PVOID,PVOID,PVOID,PVOID,PVOID) asm("RtlUnwindEx");
 390 #define RtlUnwindEx RtlUnwindEx_FIXED
 391 #endif
 392
 393 #define LJ_MSVC_EXCODE          ((DWORD)0xe06d7363)
 394 #define LJ_GCC_EXCODE           ((DWORD)0x20474343)
 395
 396 #define LJ_EXCODE               ((DWORD)0xe24c4a00)
 397 #define LJ_EXCODE_MAKE(c)       (LJ_EXCODE | (DWORD)(c))
 398 #define LJ_EXCODE_CHECK(cl)     (((cl) ^ LJ_EXCODE) <= 0xff)
 399 #define LJ_EXCODE_ERRCODE(cl)   ((int)((cl) & 0xff))
 400
 401 /* Win64 exception handler for interpreter frame. */
 402 LJ_FUNCA EXCEPTION_DISPOSITION lj_err_unwind_win64(EXCEPTION_RECORD *rec,
 403   void *cf, CONTEXT *ctx, UndocumentedDispatcherContext *dispatch)
 404 {
 405   lua_State *L = cframe_L(cf);
 406   int errcode = LJ_EXCODE_CHECK(rec->ExceptionCode) ?
 407                 LJ_EXCODE_ERRCODE(rec->ExceptionCode) : LUA_ERRRUN;
 408   if ((rec->ExceptionFlags & 6)) {  /* EH_UNWINDING|EH_EXIT_UNWIND */
 409     /* Unwind internal frames. */
 410     err_unwind(L, cf, errcode);
 411   } else {
 412     void *cf2 = err_unwind(L, cf, 0);
 413     if (cf2) {  /* We catch it, so start unwinding the upper frames. */
 414       if (rec->ExceptionCode == LJ_MSVC_EXCODE ||
 415           rec->ExceptionCode == LJ_GCC_EXCODE) {
 416 #if LJ_TARGET_WINDOWS
 417         __DestructExceptionObject(rec, 1);
 418 #endif
 419         setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
 420       } else if (!LJ_EXCODE_CHECK(rec->ExceptionCode)) {
 421         /* Don't catch access violations etc. */
 422         return ExceptionContinueSearch;
 423       }
 424       /* Unwind the stack and call all handlers for all lower C frames
 425       ** (including ourselves) again with EH_UNWINDING set. Then set
 426       ** rsp = cf, rax = errcode and jump to the specified target.
 427       */
 428       RtlUnwindEx(cf, (void *)((cframe_unwind_ff(cf2) && errcode != LUA_YIELD) ?
 429                                lj_vm_unwind_ff_eh :
 430                                lj_vm_unwind_c_eh),
 431                   rec, (void *)(uintptr_t)errcode, ctx, dispatch->HistoryTable);
 432       /* RtlUnwindEx should never return. */
 433     }
 434   }
 435   return ExceptionContinueSearch;
 436 }
 437
 438 /* Raise Windows exception. */
 439 static void err_raise_ext(int errcode)
 440 {
 441   RaiseException(LJ_EXCODE_MAKE(errcode), 1 /* EH_NONCONTINUABLE */, 0, NULL);
 442 }
 443
 444 #endif
 445
 446 /* -- Error handling ------------------------------------------------------ */
 447
 448 /* Throw error. Find catch frame, unwind stack and continue. */
 449 LJ_NOINLINE void LJ_FASTCALL lj_err_throw(lua_State *L, int errcode)
 450 {
 451   global_State *g = G(L);
 452   lj_trace_abort(g);
 453   setgcrefnull(g->jit_L);
 454   L->status = 0;
 455 #if LJ_UNWIND_EXT
 456   err_raise_ext(errcode);
 457   /*
 458   ** A return from this function signals a corrupt C stack that cannot be
 459   ** unwound. We have no choice but to call the panic function and exit.
 460   **
 461   ** Usually this is caused by a C function without unwind information.
 462   ** This should never happen on x64, but may happen if you've manually
 463   ** enabled LUAJIT_UNWIND_EXTERNAL and forgot to recompile *every*
 464   ** non-C++ file with -funwind-tables.
 465   */
 466   if (G(L)->panic)
 467     G(L)->panic(L);
 468 #else
 469   {
 470     void *cf = err_unwind(L, NULL, errcode);
 471     if (cframe_unwind_ff(cf))
 472       lj_vm_unwind_ff(cframe_raw(cf));
 473     else
 474       lj_vm_unwind_c(cframe_raw(cf), errcode);
 475   }
 476 #endif
 477   exit(EXIT_FAILURE);
 478 }
 479
 480 /* Return string object for error message. */
 481 LJ_NOINLINE GCstr *lj_err_str(lua_State *L, ErrMsg em)
 482 {
 483   return lj_str_newz(L, err2msg(em));
 484 }
 485
 486 /* Out-of-memory error. */
 487 LJ_NOINLINE void lj_err_mem(lua_State *L)
 488 {
 489   if (L->status == LUA_ERRERR+1)  /* Don't touch the stack during lua_open. */
 490     lj_vm_unwind_c(L->cframe, LUA_ERRMEM);
 491   if (curr_funcisL(L)) {
 492     L->top = curr_topL(L);
 493     if (LJ_UNLIKELY(L->top > tvref(L->maxstack))) {
 494       /* The current Lua frame violates the stack. Replace it with a dummy. */
 495       L->top = L->base;
 496       setframe_gc(L->base - 1, obj2gco(L));
 497     }
 498   }
 499   setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRMEM));
 500   lj_err_throw(L, LUA_ERRMEM);
 501 }
 502
 503 /* Find error function for runtime errors. Requires an extra stack traversal. */
 504 static ptrdiff_t finderrfunc(lua_State *L)
 505 {
 506   cTValue *frame = L->base-1, *bot = tvref(L->stack);
 507   void *cf = L->cframe;
 508   while (frame > bot && cf) {
 509     while (cframe_nres(cframe_raw(cf)) < 0) {  /* cframe without frame? */
 510       if (frame >= restorestack(L, -cframe_nres(cf)))
 511         break;
 512       if (cframe_errfunc(cf) >= 0)  /* Error handler not inherited (-1)? */
 513         return cframe_errfunc(cf);
 514       cf = cframe_prev(cf);  /* Else unwind cframe and continue searching. */
 515       if (cf == NULL)
 516         return 0;
 517     }
 518     switch (frame_typep(frame)) {
 519     case FRAME_LUA:
 520     case FRAME_LUAP:
 521       frame = frame_prevl(frame);
 522       break;
 523     case FRAME_C:
 524       cf = cframe_prev(cf);
 525       /* fallthrough */
 526     case FRAME_VARG:
 527       frame = frame_prevd(frame);
 528       break;
 529     case FRAME_CONT:
 530 #if LJ_HASFFI
 531       if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK)
 532         cf = cframe_prev(cf);
 533 #endif
 534       frame = frame_prevd(frame);
 535       break;
 536     case FRAME_CP:
 537       if (cframe_canyield(cf)) return 0;
 538       if (cframe_errfunc(cf) >= 0)
 539         return cframe_errfunc(cf);
 540       cf = cframe_prev(cf);
 541       frame = frame_prevd(frame);
 542       break;
 543     case FRAME_PCALL:
 544     case FRAME_PCALLH:
 545       if (frame_ftsz(frame) >= (ptrdiff_t)(2*sizeof(TValue)))  /* xpcall? */
 546         return savestack(L, frame-1);  /* Point to xpcall's errorfunc. */
 547       return 0;
 548     default:
 549       lua_assert(0);
 550       return 0;
 551     }
 552   }
 553   return 0;
 554 }
 555
 556 /* Runtime error. */
 557 LJ_NOINLINE void LJ_FASTCALL lj_err_run(lua_State *L)
 558 {
 559   ptrdiff_t ef = finderrfunc(L);
 560   if (ef) {
 561     TValue *errfunc, *top;
 562     lj_state_checkstack(L, LUA_MINSTACK * 2);  /* Might raise new error. */
 563     lj_trace_abort(G(L));
 564     errfunc = restorestack(L, ef);
 565     top = L->top;
 566     if (!tvisfunc(errfunc) || L->status == LUA_ERRERR) {
 567       setstrV(L, top-1, lj_err_str(L, LJ_ERR_ERRERR));
 568       lj_err_throw(L, LUA_ERRERR);
 569     }
 570     L->status = LUA_ERRERR;
 571     copyTV(L, top, top-1);
 572     copyTV(L, top-1, errfunc);
 573     L->top = top+1;
 574     lj_vm_call(L, top, 1+1);  /* Stack: |errfunc|msg| -> |msg| */
 575   }
 576   lj_err_throw(L, LUA_ERRRUN);
 577 }
 578
 579 /* Stack overflow error. */
 580 void LJ_FASTCALL lj_err_stkov(lua_State *L)
 581 {
 582   lj_debug_addloc(L, err2msg(LJ_ERR_STKOV), L->base-1, NULL);
 583   lj_err_run(L);
 584 }
 585
 586 /* Formatted runtime error message. */
 587 LJ_NORET LJ_NOINLINE static void err_msgv(lua_State *L, ErrMsg em, ...)
 588 {
 589   const char *msg;
 590   va_list argp;
 591   va_start(argp, em);
 592   if (curr_funcisL(L)) L->top = curr_topL(L);
 593   msg = lj_str_pushvf(L, err2msg(em), argp);
 594   va_end(argp);
 595   lj_debug_addloc(L, msg, L->base-1, NULL);
 596   lj_err_run(L);
 597 }
 598
 599 /* Non-vararg variant for better calling conventions. */
 600 LJ_NOINLINE void lj_err_msg(lua_State *L, ErrMsg em)
 601 {
 602   err_msgv(L, em);
 603 }
 604
 605 /* Lexer error. */
 606 LJ_NOINLINE void lj_err_lex(lua_State *L, GCstr *src, const char *tok,
 607                             BCLine line, ErrMsg em, va_list argp)
 608 {
 609   char buff[LUA_IDSIZE];
 610   const char *msg;
 611   lj_debug_shortname(buff, src);
 612   msg = lj_str_pushvf(L, err2msg(em), argp);
 613   msg = lj_str_pushf(L, "%s:%d: %s", buff, line, msg);
 614   if (tok)
 615     lj_str_pushf(L, err2msg(LJ_ERR_XNEAR), msg, tok);
 616   lj_err_throw(L, LUA_ERRSYNTAX);
 617 }
 618
 619 /* Typecheck error for operands. */
 620 LJ_NOINLINE void lj_err_optype(lua_State *L, cTValue *o, ErrMsg opm)
 621 {
 622   const char *tname = lj_typename(o);
 623   const char *opname = err2msg(opm);
 624   if (curr_funcisL(L)) {
 625     GCproto *pt = curr_proto(L);
 626     const BCIns *pc = cframe_Lpc(L) - 1;
 627     const char *oname = NULL;
 628     const char *kind = lj_debug_slotname(pt, pc, (BCReg)(o-L->base), &oname);
 629     if (kind)
 630       err_msgv(L, LJ_ERR_BADOPRT, opname, kind, oname, tname);
 631   }
 632   err_msgv(L, LJ_ERR_BADOPRV, opname, tname);
 633 }
 634
 635 /* Typecheck error for ordered comparisons. */
 636 LJ_NOINLINE void lj_err_comp(lua_State *L, cTValue *o1, cTValue *o2)
 637 {
 638   const char *t1 = lj_typename(o1);
 639   const char *t2 = lj_typename(o2);
 640   err_msgv(L, t1 == t2 ? LJ_ERR_BADCMPV : LJ_ERR_BADCMPT, t1, t2);
 641   /* This assumes the two "boolean" entries are commoned by the C compiler. */
 642 }
 643
 644 /* Typecheck error for __call. */
 645 LJ_NOINLINE void lj_err_optype_call(lua_State *L, TValue *o)
 646 {
 647   /* Gross hack if lua_[p]call or pcall/xpcall fail for a non-callable object:
 648   ** L->base still points to the caller. So add a dummy frame with L instead
 649   ** of a function. See lua_getstack().
 650   */
 651   const BCIns *pc = cframe_Lpc(L);
 652   if (((ptrdiff_t)pc & FRAME_TYPE) != FRAME_LUA) {
 653     const char *tname = lj_typename(o);
 654     setframe_pc(o, pc);
 655     setframe_gc(o, obj2gco(L));
 656     L->top = L->base = o+1;
 657     err_msgv(L, LJ_ERR_BADCALL, tname);
 658   }
 659   lj_err_optype(L, o, LJ_ERR_OPCALL);
 660 }
 661
 662 /* Error in context of caller. */
 663 LJ_NOINLINE void lj_err_callermsg(lua_State *L, const char *msg)
 664 {
 665   TValue *frame = L->base-1;
 666   TValue *pframe = NULL;
 667   if (frame_islua(frame)) {
 668     pframe = frame_prevl(frame);
 669   } else if (frame_iscont(frame)) {
 670 #if LJ_HASFFI
 671     if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK) {
 672       pframe = frame;
 673       frame = NULL;
 674     } else
 675 #endif
 676     {
 677       pframe = frame_prevd(frame);
 678 #if LJ_HASFFI
 679       /* Remove frame for FFI metamethods. */
 680       if (frame_func(frame)->c.ffid >= FF_ffi_meta___index &&
 681           frame_func(frame)->c.ffid <= FF_ffi_meta___tostring) {
 682         L->base = pframe+1;
 683         L->top = frame;
 684         setcframe_pc(cframe_raw(L->cframe), frame_contpc(frame));
 685       }
 686 #endif
 687     }
 688   }
 689   lj_debug_addloc(L, msg, pframe, frame);
 690   lj_err_run(L);
 691 }
 692
 693 /* Formatted error in context of caller. */
 694 LJ_NOINLINE void lj_err_callerv(lua_State *L, ErrMsg em, ...)
 695 {
 696   const char *msg;
 697   va_list argp;
 698   va_start(argp, em);
 699   msg = lj_str_pushvf(L, err2msg(em), argp);
 700   va_end(argp);
 701   lj_err_callermsg(L, msg);
 702 }
 703
 704 /* Error in context of caller. */
 705 LJ_NOINLINE void lj_err_caller(lua_State *L, ErrMsg em)
 706 {
 707   lj_err_callermsg(L, err2msg(em));
 708 }
 709
 710 /* Argument error message. */
 711 LJ_NORET LJ_NOINLINE static void err_argmsg(lua_State *L, int narg,
 712                                             const char *msg)
 713 {
 714   const char *fname = "?";
 715   const char *ftype = lj_debug_funcname(L, L->base - 1, &fname);
 716   if (narg < 0 && narg > LUA_REGISTRYINDEX)
 717     narg = (int)(L->top - L->base) + narg + 1;
 718   if (ftype && ftype[3] == 'h' && --narg == 0)  /* Check for "method". */
 719     msg = lj_str_pushf(L, err2msg(LJ_ERR_BADSELF), fname, msg);
 720   else
 721     msg = lj_str_pushf(L, err2msg(LJ_ERR_BADARG), narg, fname, msg);
 722   lj_err_callermsg(L, msg);
 723 }
 724
 725 /* Formatted argument error. */
 726 LJ_NOINLINE void lj_err_argv(lua_State *L, int narg, ErrMsg em, ...)
 727 {
 728   const char *msg;
 729   va_list argp;
 730   va_start(argp, em);
 731   msg = lj_str_pushvf(L, err2msg(em), argp);
 732   va_end(argp);
 733   err_argmsg(L, narg, msg);
 734 }
 735
 736 /* Argument error. */
 737 LJ_NOINLINE void lj_err_arg(lua_State *L, int narg, ErrMsg em)
 738 {
 739   err_argmsg(L, narg, err2msg(em));
 740 }
 741
 742 /* Typecheck error for arguments. */
 743 LJ_NOINLINE void lj_err_argtype(lua_State *L, int narg, const char *xname)
 744 {
 745   const char *tname, *msg;
 746   if (narg <= LUA_REGISTRYINDEX) {
 747     if (narg >= LUA_GLOBALSINDEX) {
 748       tname = lj_obj_itypename[~LJ_TTAB];
 749     } else {
 750       GCfunc *fn = curr_func(L);
 751       int idx = LUA_GLOBALSINDEX - narg;
 752       if (idx <= fn->c.nupvalues)
 753         tname = lj_typename(&fn->c.upvalue[idx-1]);
 754       else
 755         tname = lj_obj_typename[0];
 756     }
 757   } else {
 758     TValue *o = narg < 0 ? L->top + narg : L->base + narg-1;
 759     tname = o < L->top ? lj_typename(o) : lj_obj_typename[0];
 760   }
 761   msg = lj_str_pushf(L, err2msg(LJ_ERR_BADTYPE), xname, tname);
 762   err_argmsg(L, narg, msg);
 763 }
 764
 765 /* Typecheck error for arguments. */
 766 LJ_NOINLINE void lj_err_argt(lua_State *L, int narg, int tt)
 767 {
 768   lj_err_argtype(L, narg, lj_obj_typename[tt+1]);
 769 }
 770
 771 /* -- Public error handling API ------------------------------------------- */
 772
 773 LUA_API lua_CFunction lua_atpanic(lua_State *L, lua_CFunction panicf)
 774 {
 775   lua_CFunction old = G(L)->panic;
 776   G(L)->panic = panicf;
 777   return old;
 778 }
 779
 780 /* Forwarders for the public API (C calling convention and no LJ_NORET). */
 781 LUA_API int lua_error(lua_State *L)
 782 {
 783   lj_err_run(L);
 784   return 0;  /* unreachable */
 785 }
 786
 787 LUALIB_API int luaL_argerror(lua_State *L, int narg, const char *msg)
 788 {
 789   err_argmsg(L, narg, msg);
 790   return 0;  /* unreachable */
 791 }
 792
 793 LUALIB_API int luaL_typerror(lua_State *L, int narg, const char *xname)
 794 {
 795   lj_err_argtype(L, narg, xname);
 796   return 0;  /* unreachable */
 797 }
 798
 799 LUALIB_API void luaL_where(lua_State *L, int level)
 800 {
 801   int size;
 802   cTValue *frame = lj_debug_frame(L, level, &size);
 803   lj_debug_addloc(L, "", frame, size ? frame+size : NULL);
 804 }
 805
 806 LUALIB_API int luaL_error(lua_State *L, const char *fmt, ...)
 807 {
 808   const char *msg;
 809   va_list argp;
 810   va_start(argp, fmt);
 811   msg = lj_str_pushvf(L, fmt, argp);
 812   va_end(argp);
 813   lj_err_callermsg(L, msg);
 814   return 0;  /* unreachable */
 815 }
 816