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Define NO_UNWIND
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I hope that I understand this feature correctly... it's for allowing C++
exceptions to propagate through LuaJIT? (e.g. C++ calls LuaJIT calls C++
throws exception?)

Removing with this rationale:
- Complex hairy code.
- Limited value.
- Looks straightforward to re-introduce if needed.
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@lukego
lukego committed Mar 16, 2017
1 parent 521a874 commit f7dc94a
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Showing 5 changed files with 2 additions and 408 deletions.
3 changes: 2 additions & 1 deletion src/ifdef-defile
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Expand Up @@ -3,11 +3,13 @@
#define LJ_GC64 1
#define LJ_HASFFI 1
#define LJ_HASJIT 1
#define LJ_NOUNWIND 1
#define LUAJIT_DISABLE_PROFILE 1
#define LUAJIT_DISABLE_VMEVENT 1
#define LUAJIT_ENABLE_GC64 1
#define LUAJIT_ENABLE_JIT 1
#undef LJ_HASPROFILE
#undef LJ_UNWIND_EXT
#undef LUAJIT_DISABLE_FFI
#undef LUAJIT_DISABLE_JIT
#undef LUAJIT_NOFFI
Expand Down Expand Up @@ -61,7 +63,6 @@
#undef LJ_ARCH_NOFFI
#undef LJ_ARCH_PPC
#undef LJ_BE
#undef LJ_NOUNWIND
#undef LJ_OS_NOJIT
#undef LJ_SOFTFP
#undef LJ_TARGET_ARM
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11 changes: 0 additions & 11 deletions src/lj_arch.h
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Expand Up @@ -152,17 +152,6 @@
#define LJ_TARGET_UNALIGNED 0
#endif

/* Various workarounds for embedded operating systems or weak C runtimes. */

#if !defined(LUAJIT_NO_UNWIND) && __GNU_COMPACT_EH__
/* NYI: no support for compact unwind specification, yet. */
#define LUAJIT_NO_UNWIND 1
#endif

#if defined(LUAJIT_NO_UNWIND) || defined(__symbian__) || LJ_TARGET_IOS || LJ_TARGET_PS3 || LJ_TARGET_PS4
#define LJ_NO_UNWIND 1
#endif

/* Compatibility with Lua 5.1 vs. 5.2. */
#ifdef LUAJIT_ENABLE_LUA52COMPAT
#define LJ_52 1
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196 changes: 0 additions & 196 deletions src/lj_err.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,53 +18,6 @@
#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. This is the default on x64,
** but needs to be manually enabled on x86/PPC for non-C++ code.
**
** - INT is faster when actually throwing errors (but this happens rarely).
** Setting up error handlers is zero-cost in any case.
**
** - 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 is the default on x64 systems and on Windows, INT is the default on all
** other systems.
**
** EXT can be manually enabled on POSIX systems using GCC and DWARF2 stack
** unwinding with -DLUAJIT_UNWIND_EXTERNAL. *All* C code must be compiled
** with -funwind-tables (or -fexceptions). This includes LuaJIT itself (set
** TARGET_CFLAGS), all of your C/Lua binding code, all loadable C modules
** and all C libraries that have callbacks which may be used to call back
** into Lua. C++ code must *not* be compiled with -fno-exceptions.
**
** EXT is mandatory on WIN64 since the calling convention has an abundance
** of callee-saved registers (rbx, rbp, rsi, rdi, r12-r15, xmm6-xmm15).
** The POSIX/x64 interpreter only saves r12/r13 for INT (e.g. PS4).
*/

#if defined(__GNUC__) && (LJ_TARGET_X64 || defined(LUAJIT_UNWIND_EXTERNAL)) && !LJ_NO_UNWIND
#define LJ_UNWIND_EXT 1
#endif

/* -- Error messages ------------------------------------------------------ */

/* Error message strings. */
Expand Down Expand Up @@ -113,23 +66,10 @@ static void *err_unwind(lua_State *L, void *stopcf, int errcode)
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) {
Expand Down Expand Up @@ -179,127 +119,6 @@ static void *err_unwind(lua_State *L, void *stopcf, int errcode)
return L; /* Anything non-NULL will do. */
}

/* -- External frame unwinding -------------------------------------------- */

#if defined(__GNUC__) && !LJ_NO_UNWIND && !LJ_ABI_WIN

/*
** 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_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))


typedef struct _Unwind_Exception
{
uint64_t exclass;
void (*excleanup)(int, struct _Unwind_Exception *);
uintptr_t p1, p2;
} __attribute__((__aligned__)) _Unwind_Exception;

extern uintptr_t _Unwind_GetCFA(_Unwind_Context *);
extern void _Unwind_SetGR(_Unwind_Context *, int, uintptr_t);
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;
UNUSED(uexclass);
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;
}
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;
}
#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);
#endif
}
return _URC_CONTINUE_UNWIND;
}

#if LJ_UNWIND_EXT
#if LJ_TARGET_OSX || defined(__OpenBSD__)
/* Sorry, no thread safety for OSX. Complain to Apple, not me. */
static _Unwind_Exception static_uex;
#else
static __thread _Unwind_Exception static_uex;
#endif

/* Raise DWARF2 exception. */
static void err_raise_ext(int errcode)
{
static_uex.exclass = LJ_UEXCLASS_MAKE(errcode);
static_uex.excleanup = NULL;
_Unwind_RaiseException(&static_uex);
}
#endif


#endif

/* -- Error handling ------------------------------------------------------ */

/* Throw error. Find catch frame, unwind stack and continue. */
Expand All @@ -309,28 +128,13 @@ LJ_NOINLINE void lj_err_throw(lua_State *L, int errcode)
lj_trace_abort(g);
setmref(g->jit_base, NULL);
L->status = 0;
#if LJ_UNWIND_EXT
err_raise_ext(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 should never happen on x64, but 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
{
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);
}

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4 changes: 0 additions & 4 deletions src/lj_frame.h
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Original file line number Diff line number Diff line change
Expand Up @@ -85,11 +85,7 @@ enum { LJ_CONT_TAILCALL, LJ_CONT_FFI_CALLBACK }; /* Special continuations. */
#define CFRAME_OFS_ERRF (3*4)
#define CFRAME_OFS_NRES (2*4)
#define CFRAME_OFS_MULTRES (0*4)
#if LJ_NO_UNWIND
#define CFRAME_SIZE (12*8)
#else
#define CFRAME_SIZE (10*8)
#endif
#define CFRAME_SIZE_JIT (CFRAME_SIZE + 16)
#define CFRAME_SHIFT_MULTRES 0

Expand Down
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