text: /*
  ** Error handling.
  ** Copyright (C) 2005-2021 Mike Pall. See Copyright Notice in luajit.h
  */
  
  #define lj_err_c
  #define LUA_CORE
  
  #include "lj_obj.h"
  #include "lj_err.h"
  #include "lj_debug.h"
  #include "lj_str.h"
  #include "lj_func.h"
  #include "lj_state.h"
  #include "lj_frame.h"
  #include "lj_ff.h"
  #include "lj_trace.h"
  #include "lj_vm.h"
  #include "lj_strfmt.h"
  
  /*
  ** LuaJIT can either use internal or external frame unwinding:
  **
  ** - Internal frame unwinding (INT) is free-standing and doesn't require
  **   any OS or library support.
  **
  ** - External frame unwinding (EXT) uses the system-provided unwind handler.
  **
  ** Pros and Cons:
  **
  ** - EXT requires unwind tables for *all* functions on the C stack between
  **   the pcall/catch and the error/throw. C modules used by Lua code can
  **   throw errors, so these need to have unwind tables, too. Transitively
  **   this applies to all system libraries used by C modules -- at least
  **   when they have callbacks which may throw an error.
  **
  ** - INT is faster when actually throwing errors, but this happens rarely.
  **   Setting up error handlers is zero-cost in any case.
  **
  ** - INT needs to save *all* callee-saved registers when entering the
  **   interpreter. EXT only needs to save those actually used inside the
  **   interpreter. JIT-compiled code may need to save some more.
  **
  ** - EXT provides full interoperability with C++ exceptions. You can throw
  **   Lua errors or C++ exceptions through a mix of Lua frames and C++ frames.
  **   C++ destructors are called as needed. C++ exceptions caught by pcall
  **   are converted to the string "C++ exception". Lua errors can be caught
  **   with catch (...) in C++.
  **
  ** - INT has only limited support for automatically catching C++ exceptions
  **   on POSIX systems using DWARF2 stack unwinding. Other systems may use
  **   the wrapper function feature. Lua errors thrown through C++ frames
  **   cannot be caught by C++ code and C++ destructors are not run.
  **
  ** - EXT can handle errors from internal helper functions that are called
  **   from JIT-compiled code (except for Windows/x86 and 32 bit ARM).
  **   INT has no choice but to call the panic handler, if this happens.
  **   Note: this is mainly relevant for out-of-memory errors.
  **
  ** EXT is the default on all systems where the toolchain produces unwind
  ** tables by default (*). This is hard-coded and/or detected in src/Makefile.
  ** You can thwart the detection with: TARGET_XCFLAGS=-DLUAJIT_UNWIND_INTERNAL
  **
  ** INT is the default on all other systems.
  **
  ** EXT can be manually enabled for toolchains that are able to produce
  ** conforming unwind tables:
  **   "TARGET_XCFLAGS=-funwind-tables -DLUAJIT_UNWIND_EXTERNAL"
  ** As explained above, *all* C code used directly or indirectly by LuaJIT
  ** must be compiled with -funwind-tables (or -fexceptions). C++ code must
  ** *not* be compiled with -fno-exceptions.
  **
  ** If you're unsure whether error handling inside the VM works correctly,
  ** try running this and check whether it prints "OK":
  **
  **   luajit -e "print(select(2, load('OK')):match('OK'))"
  **
  ** (*) Originally, toolchains only generated unwind tables for C++ code. For
  ** interoperability reasons, this can be manually enabled for plain C code,
  ** too (with -funwind-tables). With the introduction of the x64 architecture,
  ** the corresponding POSIX and Windows ABIs mandated unwind tables for all
  ** code. Over the following years most desktop and server platforms have
  ** enabled unwind tables by default on all architectures. OTOH mobile and
  ** embedded platforms do not consistently mandate unwind tables.
  */
  
  /* -- Error messages ------------------------------------------------------ */
  
  /* Error message strings. */
  LJ_DATADEF const char *lj_err_allmsg =
  #define ERRDEF(name, msg)	msg "\0"
  #include "lj_errmsg.h"
  ;
  
  /* -- Internal frame unwinding -------------------------------------------- */
  
  /* Unwind Lua stack and move error message to new top. */
  LJ_NOINLINE static void unwindstack(lua_State *L, TValue *top)
  {
  	lj_func_closeuv(L, top);
  	if (top < L->top-1) {
  		copyTV(L, top, L->top-1);
  		L->top = top+1;
  	}
  	lj_state_relimitstack(L);
  }
  
  /* Unwind until stop frame. Optionally cleanup frames. */
  static void *err_unwind(lua_State *L, void *stopcf, int errcode)
  {
  	TValue *frame = L->base-1;
  	void *cf = L->cframe;
  	while (cf) {
  		int32_t nres = cframe_nres(cframe_raw(cf));
  		if (nres < 0) {  /* C frame without Lua frame? */
  			TValue *top = restorestack(L, -nres);
  			if (frame < top) {  /* Frame reached? */
  				if (errcode) {
  					L->base = frame+1;
  					L->cframe = cframe_prev(cf);
  					unwindstack(L, top);
  				}
  				return cf;
  			}
  		}
  		if (frame <= tvref(L->stack)+LJ_FR2)
  			break;
  		switch (frame_typep(frame)) {
  		case FRAME_LUA:  /* Lua frame. */
  		case FRAME_LUAP:
  			frame = frame_prevl(frame);
  			break;
  		case FRAME_C:  /* C frame. */
  		unwind_c:
  #if LJ_UNWIND_EXT
  			if (errcode) {
  				L->base = frame_prevd(frame) + 1;
  				L->cframe = cframe_prev(cf);
  				unwindstack(L, frame - LJ_FR2);
  			} else if (cf != stopcf) {
  				cf = cframe_prev(cf);
  				frame = frame_prevd(frame);
  				break;
  			}
  			return NULL;  /* Continue unwinding. */
  #else
  			UNUSED(stopcf);
  			cf = cframe_prev(cf);
  			frame = frame_prevd(frame);
  			break;
  #endif
  		case FRAME_CP:  /* Protected C frame. */
  			if (cframe_canyield(cf)) {  /* Resume? */
  				if (errcode) {
  					hook_leave(G(L));  /* Assumes nobody uses coroutines inside hooks. */
  					L->cframe = NULL;
  					L->status = (uint8_t)errcode;
  				}
  				return cf;
  			}
  			if (errcode) {
  				L->base = frame_prevd(frame) + 1;
  				L->cframe = cframe_prev(cf);
  				unwindstack(L, frame - LJ_FR2);
  			}
  			return cf;
  		case FRAME_CONT:  /* Continuation frame. */
  			if (frame_iscont_fficb(frame))
  				goto unwind_c;
  			/* fallthrough */
  		case FRAME_VARG:  /* Vararg frame. */
  			frame = frame_prevd(frame);
  			break;
  		case FRAME_PCALL:  /* FF pcall() frame. */
  		case FRAME_PCALLH:  /* FF pcall() frame inside hook. */
  			if (errcode) {
  				if (errcode == LUA_YIELD) {
  					frame = frame_prevd(frame);
  					break;
  				}
  				if (frame_typep(frame) == FRAME_PCALL)
  					hook_leave(G(L));
  				L->base = frame_prevd(frame) + 1;
  				L->cframe = cf;
  				unwindstack(L, L->base);
  			}
  			return (void *)((intptr_t)cf | CFRAME_UNWIND_FF);
  		}
  	}
  	/* No C frame. */
  	if (errcode) {
  		L->base = tvref(L->stack)+1+LJ_FR2;
  		L->cframe = NULL;
  		unwindstack(L, L->base);
  		if (G(L)->panic)
  			G(L)->panic(L);
  		exit(EXIT_FAILURE);
  	}
  	return L;  /* Anything non-NULL will do. */
  }
  
  /* -- External frame unwinding -------------------------------------------- */
  
  #if LJ_ABI_WIN
  
  /*
  ** Someone in Redmond owes me several days of my life. A lot of this is
  ** undocumented or just plain wrong on MSDN. Some of it can be gathered
  ** from 3rd party docs or must be found by trial-and-error. They really
  ** don't want you to write your own language-specific exception handler
  ** or to interact gracefully with MSVC. :-(
  **
  ** Apparently MSVC doesn't call C++ destructors for foreign exceptions
  ** unless you compile your C++ code with /EHa. Unfortunately this means
  ** catch (...) also catches things like access violations. The use of
  ** _set_se_translator doesn't really help, because it requires /EHa, too.
  */
  
  #define WIN32_LEAN_AND_MEAN
  #include <windows.h>
  
  #if LJ_TARGET_X86
  typedef void *UndocumentedDispatcherContext;  /* Unused on x86. */
  #else
  /* Taken from: http://www.nynaeve.net/?p=99 */
  typedef struct UndocumentedDispatcherContext {
  	ULONG64 ControlPc;
  	ULONG64 ImageBase;
  	PRUNTIME_FUNCTION FunctionEntry;
  	ULONG64 EstablisherFrame;
  	ULONG64 TargetIp;
  	PCONTEXT ContextRecord;
  	void (*LanguageHandler)(void);
  	PVOID HandlerData;
  	PUNWIND_HISTORY_TABLE HistoryTable;
  	ULONG ScopeIndex;
  	ULONG Fill0;
  } UndocumentedDispatcherContext;
  #endif
  
  /* Another wild guess. */
  extern void __DestructExceptionObject(EXCEPTION_RECORD *rec, int nothrow);
  
  #if LJ_TARGET_X64 && defined(MINGW_SDK_INIT)
  /* Workaround for broken MinGW64 declaration. */
  VOID RtlUnwindEx_FIXED(PVOID,PVOID,PVOID,PVOID,PVOID,PVOID) asm("RtlUnwindEx");
  #define RtlUnwindEx RtlUnwindEx_FIXED
  #endif
  
  #define LJ_MSVC_EXCODE		((DWORD)0xe06d7363)
  #define LJ_GCC_EXCODE		((DWORD)0x20474343)
  
  #define LJ_EXCODE		((DWORD)0xe24c4a00)
  #define LJ_EXCODE_MAKE(c)	(LJ_EXCODE | (DWORD)(c))
  #define LJ_EXCODE_CHECK(cl)	(((cl) ^ LJ_EXCODE) <= 0xff)
  #define LJ_EXCODE_ERRCODE(cl)	((int)((cl) & 0xff))
  
  /* Windows exception handler for interpreter frame. */
  LJ_FUNCA int lj_err_unwind_win(EXCEPTION_RECORD *rec,
  	void *f, CONTEXT *ctx, UndocumentedDispatcherContext *dispatch)
  {
  #if LJ_TARGET_X86
  	void *cf = (char *)f - CFRAME_OFS_SEH;
  #else
  	void *cf = f;
  #endif
  	lua_State *L = cframe_L(cf);
  	int errcode = LJ_EXCODE_CHECK(rec->ExceptionCode) ?
  								LJ_EXCODE_ERRCODE(rec->ExceptionCode) : LUA_ERRRUN;
  	if ((rec->ExceptionFlags & 6)) {  /* EH_UNWINDING|EH_EXIT_UNWIND */
  		/* Unwind internal frames. */
  		err_unwind(L, cf, errcode);
  	} else {
  		void *cf2 = err_unwind(L, cf, 0);
  		if (cf2) {  /* We catch it, so start unwinding the upper frames. */
  			if (rec->ExceptionCode == LJ_MSVC_EXCODE ||
  					rec->ExceptionCode == LJ_GCC_EXCODE) {
  #if !LJ_TARGET_CYGWIN
  				__DestructExceptionObject(rec, 1);
  #endif
  				setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
  			} else if (!LJ_EXCODE_CHECK(rec->ExceptionCode)) {
  				/* Don't catch access violations etc. */
  				return 1;  /* ExceptionContinueSearch */
  			}
  #if LJ_TARGET_X86
  			UNUSED(ctx);
  			UNUSED(dispatch);
  			/* Call all handlers for all lower C frames (including ourselves) again
  			** with EH_UNWINDING set. Then call the specified function, passing cf
  			** and errcode.
  			*/
  			lj_vm_rtlunwind(cf, (void *)rec,
  				(cframe_unwind_ff(cf2) && errcode != LUA_YIELD) ?
  				(void *)lj_vm_unwind_ff : (void *)lj_vm_unwind_c, errcode);
  			/* lj_vm_rtlunwind does not return. */
  #else
  			/* Unwind the stack and call all handlers for all lower C frames
  			** (including ourselves) again with EH_UNWINDING set. Then set
  			** stack pointer = cf, result = errcode and jump to the specified target.
  			*/
  			RtlUnwindEx(cf, (void *)((cframe_unwind_ff(cf2) && errcode != LUA_YIELD) ?
  															 lj_vm_unwind_ff_eh :
  															 lj_vm_unwind_c_eh),
  									rec, (void *)(uintptr_t)errcode, ctx, dispatch->HistoryTable);
  			/* RtlUnwindEx should never return. */
  #endif
  		}
  	}
  	return 1;  /* ExceptionContinueSearch */
  }
  
  #if LJ_UNWIND_JIT
  
  #if LJ_TARGET_X64
  #define CONTEXT_REG_PC	Rip
  #elif LJ_TARGET_ARM64
  #define CONTEXT_REG_PC	Pc
  #else
  #error "NYI: Windows arch-specific unwinder for JIT-compiled code"
  #endif
  
  /* Windows unwinder for JIT-compiled code. */
  static void err_unwind_win_jit(global_State *g, int errcode)
  {
  	CONTEXT ctx;
  	UNWIND_HISTORY_TABLE hist;
  
  	memset(&hist, 0, sizeof(hist));
  	RtlCaptureContext(&ctx);
  	while (1) {
  		uintptr_t frame, base, addr = ctx.CONTEXT_REG_PC;
  		void *hdata;
  		PRUNTIME_FUNCTION func = RtlLookupFunctionEntry(addr, &base, &hist);
  		if (!func) {  /* Found frame without .pdata: must be JIT-compiled code. */
  			ExitNo exitno;
  			uintptr_t stub = lj_trace_unwind(G2J(g), addr - sizeof(MCode), &exitno);
  			if (stub) {  /* Jump to side exit to unwind the trace. */
  				ctx.CONTEXT_REG_PC = stub;
  				G2J(g)->exitcode = errcode;
  				RtlRestoreContext(&ctx, NULL);  /* Does not return. */
  			}
  			break;
  		}
  		RtlVirtualUnwind(UNW_FLAG_NHANDLER, base, addr, func,
  										 &ctx, &hdata, &frame, NULL);
  		if (!addr) break;
  	}
  	/* Unwinding failed, if we end up here. */
  }
  #endif
  
  /* Raise Windows exception. */
  static void err_raise_ext(global_State *g, int errcode)
  {
  #if LJ_UNWIND_JIT
  	if (tvref(g->jit_base)) {
  		err_unwind_win_jit(g, errcode);
  		return;  /* Unwinding failed. */
  	}
  #elif LJ_HASJIT
  	/* Cannot catch on-trace errors for Windows/x86 SEH. Unwind to interpreter. */
  	setmref(g->jit_base, NULL);
  #endif
  	UNUSED(g);
  	RaiseException(LJ_EXCODE_MAKE(errcode), 1 /* EH_NONCONTINUABLE */, 0, NULL);
  }
  
  #elif !LJ_NO_UNWIND && (defined(__GNUC__) || defined(__clang__))
  
  /*
  ** We have to use our own definitions instead of the mandatory (!) unwind.h,
  ** since various OS, distros and compilers mess up the header installation.
  */
  
  typedef struct _Unwind_Context _Unwind_Context;
  
  #define _URC_OK			0
  #define _URC_FATAL_PHASE2_ERROR	2
  #define _URC_FATAL_PHASE1_ERROR	3
  #define _URC_HANDLER_FOUND	6
  #define _URC_INSTALL_CONTEXT	7
  #define _URC_CONTINUE_UNWIND	8
  #define _URC_FAILURE		9
  
  #define LJ_UEXCLASS		0x4c55414a49543200ULL	/* LUAJIT2\0 */
  #define LJ_UEXCLASS_MAKE(c)	(LJ_UEXCLASS | (uint64_t)(c))
  #define LJ_UEXCLASS_CHECK(cl)	(((cl) ^ LJ_UEXCLASS) <= 0xff)
  #define LJ_UEXCLASS_ERRCODE(cl)	((int)((cl) & 0xff))
  
  #if !LJ_TARGET_ARM
  
  typedef struct _Unwind_Exception
  {
  	uint64_t exclass;
  	void (*excleanup)(int, struct _Unwind_Exception *);
  	uintptr_t p1, p2;
  } __attribute__((__aligned__)) _Unwind_Exception;
  #define UNWIND_EXCEPTION_TYPE	_Unwind_Exception
  
  extern uintptr_t _Unwind_GetCFA(_Unwind_Context *);
  extern void _Unwind_SetGR(_Unwind_Context *, int, uintptr_t);
  extern uintptr_t _Unwind_GetIP(_Unwind_Context *);
  extern void _Unwind_SetIP(_Unwind_Context *, uintptr_t);
  extern void _Unwind_DeleteException(_Unwind_Exception *);
  extern int _Unwind_RaiseException(_Unwind_Exception *);
  
  #define _UA_SEARCH_PHASE	1
  #define _UA_CLEANUP_PHASE	2
  #define _UA_HANDLER_FRAME	4
  #define _UA_FORCE_UNWIND	8
  
  /* DWARF2 personality handler referenced from interpreter .eh_frame. */
  LJ_FUNCA int lj_err_unwind_dwarf(int version, int actions,
  	uint64_t uexclass, _Unwind_Exception *uex, _Unwind_Context *ctx)
  {
  	void *cf;
  	lua_State *L;
  	if (version != 1)
  		return _URC_FATAL_PHASE1_ERROR;
  	cf = (void *)_Unwind_GetCFA(ctx);
  	L = cframe_L(cf);
  	if ((actions & _UA_SEARCH_PHASE)) {
  #if LJ_UNWIND_EXT
  		if (err_unwind(L, cf, 0) == NULL)
  			return _URC_CONTINUE_UNWIND;
  #endif
  		if (!LJ_UEXCLASS_CHECK(uexclass)) {
  			setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
  		}
  		return _URC_HANDLER_FOUND;
  	}
  	if ((actions & _UA_CLEANUP_PHASE)) {
  		int errcode;
  		if (LJ_UEXCLASS_CHECK(uexclass)) {
  			errcode = LJ_UEXCLASS_ERRCODE(uexclass);
  		} else {
  			if ((actions & _UA_HANDLER_FRAME))
  				_Unwind_DeleteException(uex);
  			errcode = LUA_ERRRUN;
  		}
  #if LJ_UNWIND_EXT
  		cf = err_unwind(L, cf, errcode);
  		if ((actions & _UA_FORCE_UNWIND)) {
  			return _URC_CONTINUE_UNWIND;
  		} else if (cf) {
  			_Unwind_SetGR(ctx, LJ_TARGET_EHRETREG, errcode);
  			_Unwind_SetIP(ctx, (uintptr_t)(cframe_unwind_ff(cf) ?
  																		 lj_vm_unwind_ff_eh :
  																		 lj_vm_unwind_c_eh));
  			return _URC_INSTALL_CONTEXT;
  		}
  #if LJ_TARGET_X86ORX64
  		else if ((actions & _UA_HANDLER_FRAME)) {
  			/* Workaround for ancient libgcc bug. Still present in RHEL 5.5. :-/
  			** Real fix: http://gcc.gnu.org/viewcvs/trunk/gcc/unwind-dw2.c?r1=121165&r2=124837&pathrev=153877&diff_format=h
  			*/
  			_Unwind_SetGR(ctx, LJ_TARGET_EHRETREG, errcode);
  			_Unwind_SetIP(ctx, (uintptr_t)lj_vm_unwind_rethrow);
  			return _URC_INSTALL_CONTEXT;
  		}
  #endif
  #else
  		/* This is not the proper way to escape from the unwinder. We get away with
  		** it on non-x64 because the interpreter restores all callee-saved regs.
  		*/
  		lj_err_throw(L, errcode);
  #if LJ_TARGET_X64
  #error "Broken build system -- only use the provided Makefiles!"
  #endif
  #endif
  	}
  	return _URC_CONTINUE_UNWIND;
  }
  
  #if LJ_UNWIND_EXT && defined(LUA_USE_ASSERT)
  struct dwarf_eh_bases { void *tbase, *dbase, *func; };
  extern const void *_Unwind_Find_FDE(void *pc, struct dwarf_eh_bases *bases);
  
  /* Verify that external error handling actually has a chance to work. */
  void lj_err_verify(void)
  {
  	struct dwarf_eh_bases ehb;
  	lj_assertX(_Unwind_Find_FDE((void *)lj_err_throw, &ehb), "broken build: external frame unwinding enabled, but missing -funwind-tables");
  	lj_assertX(_Unwind_Find_FDE((void *)_Unwind_RaiseException, &ehb), "broken build: external frame unwinding enabled, but system libraries have no unwind tables");
  }
  #endif
  
  #if LJ_UNWIND_JIT
  /* DWARF2 personality handler for JIT-compiled code. */
  static int err_unwind_jit(int version, int actions,
  	uint64_t uexclass, _Unwind_Exception *uex, _Unwind_Context *ctx)
  {
  	/* NYI: FFI C++ exception interoperability. */
  	if (version != 1 || !LJ_UEXCLASS_CHECK(uexclass))
  		return _URC_FATAL_PHASE1_ERROR;
  	if ((actions & _UA_SEARCH_PHASE)) {
  		return _URC_HANDLER_FOUND;
  	}
  	if ((actions & _UA_CLEANUP_PHASE)) {
  		global_State *g = *(global_State **)(uex+1);
  		ExitNo exitno;
  		uintptr_t addr = _Unwind_GetIP(ctx);  /* Return address _after_ call. */
  		uintptr_t stub = lj_trace_unwind(G2J(g), addr - sizeof(MCode), &exitno);
  		lj_assertG(tvref(g->jit_base), "unexpected throw across mcode frame");
  		if (stub) {  /* Jump to side exit to unwind the trace. */
  			G2J(g)->exitcode = LJ_UEXCLASS_ERRCODE(uexclass);
  #ifdef LJ_TARGET_MIPS
  			_Unwind_SetGR(ctx, 4, stub);
  			_Unwind_SetGR(ctx, 5, exitno);
  			_Unwind_SetIP(ctx, (uintptr_t)(void *)lj_vm_unwind_stub);
  #else
  			_Unwind_SetIP(ctx, stub);
  #endif
  			return _URC_INSTALL_CONTEXT;
  		}
  		return _URC_FATAL_PHASE2_ERROR;
  	}
  	return _URC_FATAL_PHASE1_ERROR;
  }
  
  /* DWARF2 template frame info for JIT-compiled code.
  **
  ** After copying the template to the start of the mcode segment,
  ** the frame handler function and the code size is patched.
  ** The frame handler always installs a new context to jump to the exit,
  ** so don't bother to add any unwind opcodes.
  */
  static const uint8_t err_frame_jit_template[] = {
  #if LJ_BE
  	0,0,0,
  #endif
  	LJ_64 ? 0x1c : 0x14,  /* CIE length. */
  #if LJ_LE
  	0,0,0,
  #endif
  	0,0,0,0, 1, 'z','P','R',0,  /* CIE mark, CIE version, augmentation. */
  	1, LJ_64 ? 0x78 : 0x7c, LJ_TARGET_EHRAREG,  /* Code/data align, RA. */
  #if LJ_64
  	10, 0, 0,0,0,0,0,0,0,0, 0x1b,  /* Aug. data ABS handler, PCREL|SDATA4 code. */
  	0,0,0,0,0,  /* Alignment. */
  #else
  	6, 0, 0,0,0,0, 0x1b,  /* Aug. data ABS handler, PCREL|SDATA4 code. */
  	0,  /* Alignment. */
  #endif
  #if LJ_BE
  	0,0,0,
  #endif
  	LJ_64 ? 0x14 : 0x10,  /* FDE length. */
  	0,0,0,
  	LJ_64 ? 0x24 : 0x1c,  /* CIE offset. */
  	0,0,0,
  	LJ_64 ? 0x14 : 0x10,  /* Code offset. After Final FDE. */
  #if LJ_LE
  	0,0,0,
  #endif
  	0,0,0,0, 0, 0,0,0, /* Code size, augmentation length, alignment. */
  #if LJ_64
  	0,0,0,0,  /* Alignment. */
  #endif
  	0,0,0,0  /* Final FDE. */
  };
  
  #define ERR_FRAME_JIT_OFS_HANDLER	0x12
  #define ERR_FRAME_JIT_OFS_FDE		(LJ_64 ? 0x20 : 0x18)
  #define ERR_FRAME_JIT_OFS_CODE_SIZE	(LJ_64 ? 0x2c : 0x24)
  #if LJ_TARGET_OSX
  #define ERR_FRAME_JIT_OFS_REGISTER	ERR_FRAME_JIT_OFS_FDE
  #else
  #define ERR_FRAME_JIT_OFS_REGISTER	0
  #endif
  
  extern void __register_frame(const void *);
  extern void __deregister_frame(const void *);
  
  uint8_t *lj_err_register_mcode(void *base, size_t sz, uint8_t *info)
  {
  	void **handler;
  	memcpy(info, err_frame_jit_template, sizeof(err_frame_jit_template));
  	handler = (void *)err_unwind_jit;
  	memcpy(info + ERR_FRAME_JIT_OFS_HANDLER, &handler, sizeof(handler));
  	*(uint32_t *)(info + ERR_FRAME_JIT_OFS_CODE_SIZE) =
  		(uint32_t)(sz - sizeof(err_frame_jit_template) - (info - (uint8_t *)base));
  	__register_frame(info + ERR_FRAME_JIT_OFS_REGISTER);
  #ifdef LUA_USE_ASSERT
  	{
  		struct dwarf_eh_bases ehb;
  		lj_assertX(_Unwind_Find_FDE(info + sizeof(err_frame_jit_template)+1, &ehb),
  							 "bad JIT unwind table registration");
  	}
  #endif
  	return info + sizeof(err_frame_jit_template);
  }
  
  void lj_err_deregister_mcode(void *base, size_t sz, uint8_t *info)
  {
  	UNUSED(base); UNUSED(sz);
  	__deregister_frame(info + ERR_FRAME_JIT_OFS_REGISTER);
  }
  #endif
  
  #else /* LJ_TARGET_ARM */
  
  #define _US_VIRTUAL_UNWIND_FRAME	0
  #define _US_UNWIND_FRAME_STARTING	1
  #define _US_ACTION_MASK			3
  #define _US_FORCE_UNWIND		8
  
  typedef struct _Unwind_Control_Block _Unwind_Control_Block;
  #define UNWIND_EXCEPTION_TYPE	_Unwind_Control_Block
  
  struct _Unwind_Control_Block {
  	uint64_t exclass;
  	uint32_t misc[20];
  };
  
  extern int _Unwind_RaiseException(_Unwind_Control_Block *);
  extern int __gnu_unwind_frame(_Unwind_Control_Block *, _Unwind_Context *);
  extern int _Unwind_VRS_Set(_Unwind_Context *, int, uint32_t, int, void *);
  extern int _Unwind_VRS_Get(_Unwind_Context *, int, uint32_t, int, void *);
  
  static inline uint32_t _Unwind_GetGR(_Unwind_Context *ctx, int r)
  {
  	uint32_t v;
  	_Unwind_VRS_Get(ctx, 0, r, 0, &v);
  	return v;
  }
  
  static inline void _Unwind_SetGR(_Unwind_Context *ctx, int r, uint32_t v)
  {
  	_Unwind_VRS_Set(ctx, 0, r, 0, &v);
  }
  
  extern void lj_vm_unwind_ext(void);
  
  /* ARM unwinder personality handler referenced from interpreter .ARM.extab. */
  LJ_FUNCA int lj_err_unwind_arm(int state, _Unwind_Control_Block *ucb,
  															 _Unwind_Context *ctx)
  {
  	void *cf = (void *)_Unwind_GetGR(ctx, 13);
  	lua_State *L = cframe_L(cf);
  	int errcode;
  
  	switch ((state & _US_ACTION_MASK)) {
  	case _US_VIRTUAL_UNWIND_FRAME:
  		if ((state & _US_FORCE_UNWIND)) break;
  		return _URC_HANDLER_FOUND;
  	case _US_UNWIND_FRAME_STARTING:
  		if (LJ_UEXCLASS_CHECK(ucb->exclass)) {
  			errcode = LJ_UEXCLASS_ERRCODE(ucb->exclass);
  		} else {
  			errcode = LUA_ERRRUN;
  			setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRCPP));
  		}
  		cf = err_unwind(L, cf, errcode);
  		if ((state & _US_FORCE_UNWIND) || cf == NULL) break;
  		_Unwind_SetGR(ctx, 15, (uint32_t)lj_vm_unwind_ext);
  		_Unwind_SetGR(ctx, 0, (uint32_t)ucb);
  		_Unwind_SetGR(ctx, 1, (uint32_t)errcode);
  		_Unwind_SetGR(ctx, 2, cframe_unwind_ff(cf) ?
  														(uint32_t)lj_vm_unwind_ff_eh :
  														(uint32_t)lj_vm_unwind_c_eh);
  		return _URC_INSTALL_CONTEXT;
  	default:
  		return _URC_FAILURE;
  	}
  	if (__gnu_unwind_frame(ucb, ctx) != _URC_OK)
  		return _URC_FAILURE;
  #ifdef LUA_USE_ASSERT
  	/* We should never get here unless this is a forced unwind aka backtrace. */
  	if (_Unwind_GetGR(ctx, 0) == 0xff33aa77) {
  		_Unwind_SetGR(ctx, 0, 0xff33aa88);
  	}
  #endif
  	return _URC_CONTINUE_UNWIND;
  }
  
  #if LJ_UNWIND_EXT && defined(LUA_USE_ASSERT)
  typedef int (*_Unwind_Trace_Fn)(_Unwind_Context *, void *);
  extern int _Unwind_Backtrace(_Unwind_Trace_Fn, void *);
  
  static int err_verify_bt(_Unwind_Context *ctx, int *got)
  {
  	if (_Unwind_GetGR(ctx, 0) == 0xff33aa88) { *got = 2; }
  	else if (*got == 0) { *got = 1; _Unwind_SetGR(ctx, 0, 0xff33aa77); }
  	return _URC_OK;
  }
  
  /* Verify that external error handling actually has a chance to work. */
  void lj_err_verify(void)
  {
  	int got = 0;
  	_Unwind_Backtrace((_Unwind_Trace_Fn)err_verify_bt, &got);
  	lj_assertX(got == 2, "broken build: external frame unwinding enabled, but missing -funwind-tables");
  }
  #endif
  
  /*
  ** Note: LJ_UNWIND_JIT is not implemented for 32 bit ARM.
  **
  ** The quirky ARM unwind API doesn't have __register_frame().
  ** A potential workaround might involve _Unwind_Backtrace.
  ** But most 32 bit ARM targets don't qualify for LJ_UNWIND_EXT, anyway,
  ** since they are built without unwind tables by default.
  */
  
  #endif /* LJ_TARGET_ARM */
  
  
  #if LJ_UNWIND_EXT
  static __thread struct {
  	UNWIND_EXCEPTION_TYPE ex;
  	global_State *g;
  } static_uex;
  
  /* Raise external exception. */
  static void err_raise_ext(global_State *g, int errcode)
  {
  	memset(&static_uex, 0, sizeof(static_uex));
  	static_uex.ex.exclass = LJ_UEXCLASS_MAKE(errcode);
  	static_uex.g = g;
  	_Unwind_RaiseException(&static_uex.ex);
  }
  
  #endif
  
  #endif
  
  /* -- Error handling ------------------------------------------------------ */
  
  /* Throw error. Find catch frame, unwind stack and continue. */
  LJ_NOINLINE void LJ_FASTCALL lj_err_throw(lua_State *L, int errcode)
  {
  	global_State *g = G(L);
  	lj_trace_abort(g);
  	L->status = LUA_OK;
  #if LJ_UNWIND_EXT
  	err_raise_ext(g, errcode);
  	/*
  	** A return from this function signals a corrupt C stack that cannot be
  	** unwound. We have no choice but to call the panic function and exit.
  	**
  	** Usually this is caused by a C function without unwind information.
  	** This may happen if you've manually enabled LUAJIT_UNWIND_EXTERNAL
  	** and forgot to recompile *every* non-C++ file with -funwind-tables.
  	*/
  	if (G(L)->panic)
  		G(L)->panic(L);
  #else
  #if LJ_HASJIT
  	setmref(g->jit_base, NULL);
  #endif
  	{
  		void *cf = err_unwind(L, NULL, errcode);
  		if (cframe_unwind_ff(cf))
  			lj_vm_unwind_ff(cframe_raw(cf));
  		else
  			lj_vm_unwind_c(cframe_raw(cf), errcode);
  	}
  #endif
  	exit(EXIT_FAILURE);
  }
  
  /* Return string object for error message. */
  LJ_NOINLINE GCstr *lj_err_str(lua_State *L, ErrMsg em)
  {
  	return lj_str_newz(L, err2msg(em));
  }
  
  /* Out-of-memory error. */
  LJ_NOINLINE void lj_err_mem(lua_State *L)
  {
  	if (L->status == LUA_ERRERR+1)  /* Don't touch the stack during lua_open. */
  		lj_vm_unwind_c(L->cframe, LUA_ERRMEM);
  	setstrV(L, L->top++, lj_err_str(L, LJ_ERR_ERRMEM));
  	lj_err_throw(L, LUA_ERRMEM);
  }
  
  /* Find error function for runtime errors. Requires an extra stack traversal. */
  static ptrdiff_t finderrfunc(lua_State *L)
  {
  	cTValue *frame = L->base-1, *bot = tvref(L->stack)+LJ_FR2;
  	void *cf = L->cframe;
  	while (frame > bot && cf) {
  		while (cframe_nres(cframe_raw(cf)) < 0) {  /* cframe without frame? */
  			if (frame >= restorestack(L, -cframe_nres(cf)))
  				break;
  			if (cframe_errfunc(cf) >= 0)  /* Error handler not inherited (-1)? */
  				return cframe_errfunc(cf);
  			cf = cframe_prev(cf);  /* Else unwind cframe and continue searching. */
  			if (cf == NULL)
  				return 0;
  		}
  		switch (frame_typep(frame)) {
  		case FRAME_LUA:
  		case FRAME_LUAP:
  			frame = frame_prevl(frame);
  			break;
  		case FRAME_C:
  			cf = cframe_prev(cf);
  			/* fallthrough */
  		case FRAME_VARG:
  			frame = frame_prevd(frame);
  			break;
  		case FRAME_CONT:
  			if (frame_iscont_fficb(frame))
  				cf = cframe_prev(cf);
  			frame = frame_prevd(frame);
  			break;
  		case FRAME_CP:
  			if (cframe_canyield(cf)) return 0;
  			if (cframe_errfunc(cf) >= 0)
  				return cframe_errfunc(cf);
  			cf = cframe_prev(cf);
  			frame = frame_prevd(frame);
  			break;
  		case FRAME_PCALL:
  		case FRAME_PCALLH:
  			if (frame_func(frame_prevd(frame))->c.ffid == FF_xpcall)
  				return savestack(L, frame_prevd(frame)+1);  /* xpcall's errorfunc. */
  			return 0;
  		default:
  			lj_assertL(0, "bad frame type");
  			return 0;
  		}
  	}
  	return 0;
  }
  
  /* Runtime error. */
  LJ_NOINLINE void LJ_FASTCALL lj_err_run(lua_State *L)
  {
  	ptrdiff_t ef = (LJ_HASJIT && tvref(G(L)->jit_base)) ? 0 : finderrfunc(L);
  	if (ef) {
  		TValue *errfunc = restorestack(L, ef);
  		TValue *top = L->top;
  		lj_trace_abort(G(L));
  		if (!tvisfunc(errfunc) || L->status == LUA_ERRERR) {
  			setstrV(L, top-1, lj_err_str(L, LJ_ERR_ERRERR));
  			lj_err_throw(L, LUA_ERRERR);
  		}
  		L->status = LUA_ERRERR;
  		copyTV(L, top+LJ_FR2, top-1);
  		copyTV(L, top-1, errfunc);
  		if (LJ_FR2) setnilV(top++);
  		L->top = top+1;
  		lj_vm_call(L, top, 1+1);  /* Stack: |errfunc|msg| -> |msg| */
  	}
  	lj_err_throw(L, LUA_ERRRUN);
  }
  
  #if LJ_HASJIT
  LJ_NOINLINE void LJ_FASTCALL lj_err_trace(lua_State *L, int errcode)
  {
  	if (errcode == LUA_ERRRUN)
  		lj_err_run(L);
  	else
  		lj_err_throw(L, errcode);
  }
  #endif
  
  /* Formatted runtime error message. */
  LJ_NORET LJ_NOINLINE static void err_msgv(lua_State *L, ErrMsg em, ...)
  {
  	const char *msg;
  	va_list argp;
  	va_start(argp, em);
  	if (curr_funcisL(L)) L->top = curr_topL(L);
  	msg = lj_strfmt_pushvf(L, err2msg(em), argp);
  	va_end(argp);
  	lj_debug_addloc(L, msg, L->base-1, NULL);
  	lj_err_run(L);
  }
  
  /* Non-vararg variant for better calling conventions. */
  LJ_NOINLINE void lj_err_msg(lua_State *L, ErrMsg em)
  {
  	err_msgv(L, em);
  }
  
  /* Lexer error. */
  LJ_NOINLINE void lj_err_lex(lua_State *L, GCstr *src, const char *tok,
  														BCLine line, ErrMsg em, va_list argp)
  {
  	char buff[LUA_IDSIZE];
  	const char *msg;
  	lj_debug_shortname(buff, src, line);
  	msg = lj_strfmt_pushvf(L, err2msg(em), argp);
  	msg = lj_strfmt_pushf(L, "%s:%d: %s", buff, line, msg);
  	if (tok)
  		lj_strfmt_pushf(L, err2msg(LJ_ERR_XNEAR), msg, tok);
  	lj_err_throw(L, LUA_ERRSYNTAX);
  }
  
  /* Typecheck error for operands. */
  LJ_NOINLINE void lj_err_optype(lua_State *L, cTValue *o, ErrMsg opm)
  {
  	const char *tname = lj_typename(o);
  	const char *opname = err2msg(opm);
  	if (curr_funcisL(L)) {
  		GCproto *pt = curr_proto(L);
  		const BCIns *pc = cframe_Lpc(L) - 1;
  		const char *oname = NULL;
  		const char *kind = lj_debug_slotname(pt, pc, (BCReg)(o-L->base), &oname);
  		if (kind)
  			err_msgv(L, LJ_ERR_BADOPRT, opname, kind, oname, tname);
  	}
  	err_msgv(L, LJ_ERR_BADOPRV, opname, tname);
  }
  
  /* Typecheck error for ordered comparisons. */
  LJ_NOINLINE void lj_err_comp(lua_State *L, cTValue *o1, cTValue *o2)
  {
  	const char *t1 = lj_typename(o1);
  	const char *t2 = lj_typename(o2);
  	err_msgv(L, t1 == t2 ? LJ_ERR_BADCMPV : LJ_ERR_BADCMPT, t1, t2);
  	/* This assumes the two "boolean" entries are commoned by the C compiler. */
  }
  
  /* Typecheck error for __call. */
  LJ_NOINLINE void lj_err_optype_call(lua_State *L, TValue *o)
  {
  	/* Gross hack if lua_[p]call or pcall/xpcall fail for a non-callable object:
  	** L->base still points to the caller. So add a dummy frame with L instead
  	** of a function. See lua_getstack().
  	*/
  	const BCIns *pc = cframe_Lpc(L);
  	if (((ptrdiff_t)pc & FRAME_TYPE) != FRAME_LUA) {
  		const char *tname = lj_typename(o);
  		setframe_gc(o, obj2gco(L), LJ_TTHREAD);
  		if (LJ_FR2) o++;
  		setframe_pc(o, pc);
  		L->top = L->base = o+1;
  		err_msgv(L, LJ_ERR_BADCALL, tname);
  	}
  	lj_err_optype(L, o, LJ_ERR_OPCALL);
  }
  
  /* Error in context of caller. */
  LJ_NOINLINE void lj_err_callermsg(lua_State *L, const char *msg)
  {
  	TValue *frame = L->base-1;
  	TValue *pframe = NULL;
  	if (frame_islua(frame)) {
  		pframe = frame_prevl(frame);
  	} else if (frame_iscont(frame)) {
  		if (frame_iscont_fficb(frame)) {
  			pframe = frame;
  			frame = NULL;
  		} else {
  			pframe = frame_prevd(frame);
  #if LJ_HASFFI
  			/* Remove frame for FFI metamethods. */
  			if (frame_func(frame)->c.ffid >= FF_ffi_meta___index &&
  					frame_func(frame)->c.ffid <= FF_ffi_meta___tostring) {
  				L->base = pframe+1;
  				L->top = frame;
  				setcframe_pc(cframe_raw(L->cframe), frame_contpc(frame));
  			}
  #endif
  		}
  	}
  	lj_debug_addloc(L, msg, pframe, frame);
  	lj_err_run(L);
  }
  
  /* Formatted error in context of caller. */
  LJ_NOINLINE void lj_err_callerv(lua_State *L, ErrMsg em, ...)
  {
  	const char *msg;
  	va_list argp;
  	va_start(argp, em);
  	msg = lj_strfmt_pushvf(L, err2msg(em), argp);
  	va_end(argp);
  	lj_err_callermsg(L, msg);
  }
  
  /* Error in context of caller. */
  LJ_NOINLINE void lj_err_caller(lua_State *L, ErrMsg em)
  {
  	lj_err_callermsg(L, err2msg(em));
  }
  
  /* Argument error message. */
  LJ_NORET LJ_NOINLINE static void err_argmsg(lua_State *L, int narg,
  																						const char *msg)
  {
  	const char *fname = "?";
  	const char *ftype = lj_debug_funcname(L, L->base - 1, &fname);
  	if (narg < 0 && narg > LUA_REGISTRYINDEX)
  		narg = (int)(L->top - L->base) + narg + 1;
  	if (ftype && ftype[3] == 'h' && --narg == 0)  /* Check for "method". */
  		msg = lj_strfmt_pushf(L, err2msg(LJ_ERR_BADSELF), fname, msg);
  	else
  		msg = lj_strfmt_pushf(L, err2msg(LJ_ERR_BADARG), narg, fname, msg);
  	lj_err_callermsg(L, msg);
  }
  
  /* Formatted argument error. */
  LJ_NOINLINE void lj_err_argv(lua_State *L, int narg, ErrMsg em, ...)
  {
  	const char *msg;
  	va_list argp;
  	va_start(argp, em);
  	msg = lj_strfmt_pushvf(L, err2msg(em), argp);
  	va_end(argp);
  	err_argmsg(L, narg, msg);
  }
  
  /* Argument error. */
  LJ_NOINLINE void lj_err_arg(lua_State *L, int narg, ErrMsg em)
  {
  	err_argmsg(L, narg, err2msg(em));
  }
  
  /* Typecheck error for arguments. */
  LJ_NOINLINE void lj_err_argtype(lua_State *L, int narg, const char *xname)
  {
  	const char *tname, *msg;
  	if (narg <= LUA_REGISTRYINDEX) {
  		if (narg >= LUA_GLOBALSINDEX) {
  			tname = lj_obj_itypename[~LJ_TTAB];
  		} else {
  			GCfunc *fn = curr_func(L);
  			int idx = LUA_GLOBALSINDEX - narg;
  			if (idx <= fn->c.nupvalues)
  				tname = lj_typename(&fn->c.upvalue[idx-1]);
  			else
  				tname = lj_obj_typename[0];
  		}
  	} else {
  		TValue *o = narg < 0 ? L->top + narg : L->base + narg-1;
  		tname = o < L->top ? lj_typename(o) : lj_obj_typename[0];
  	}
  	msg = lj_strfmt_pushf(L, err2msg(LJ_ERR_BADTYPE), xname, tname);
  	err_argmsg(L, narg, msg);
  }
  
  /* Typecheck error for arguments. */
  LJ_NOINLINE void lj_err_argt(lua_State *L, int narg, int tt)
  {
  	lj_err_argtype(L, narg, lj_obj_typename[tt+1]);
  }
  
  /* -- Public error handling API ------------------------------------------- */
  
  LUA_API lua_CFunction lua_atpanic(lua_State *L, lua_CFunction panicf)
  {
  	lua_CFunction old = G(L)->panic;
  	G(L)->panic = panicf;
  	return old;
  }
  
  /* Forwarders for the public API (C calling convention and no LJ_NORET). */
  LUA_API int lua_error(lua_State *L)
  {
  	lj_err_run(L);
  	return 0;  /* unreachable */
  }
  
  LUALIB_API int luaL_argerror(lua_State *L, int narg, const char *msg)
  {
  	err_argmsg(L, narg, msg);
  	return 0;  /* unreachable */
  }
  
  LUALIB_API int luaL_typerror(lua_State *L, int narg, const char *xname)
  {
  	lj_err_argtype(L, narg, xname);
  	return 0;  /* unreachable */
  }
  
  LUALIB_API void luaL_where(lua_State *L, int level)
  {
  	int size;
  	cTValue *frame = lj_debug_frame(L, level, &size);
  	lj_debug_addloc(L, "", frame, size ? frame+size : NULL);
  }
  
  LUALIB_API int luaL_error(lua_State *L, const char *fmt, ...)
  {
  	const char *msg;
  	va_list argp;
  	va_start(argp, fmt);
  	msg = lj_strfmt_pushvf(L, fmt, argp);
  	va_end(argp);
  	lj_err_callermsg(L, msg);
  	return 0;  /* unreachable */
  }
  
  