1//===------------------------- cxa_exception.cpp --------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//
8// This file implements the "Exception Handling APIs"
9// https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
10//
11//===----------------------------------------------------------------------===//
12
13#include "cxxabi.h"
14
15#include <exception> // for std::terminate
16#include <string.h> // for memset
17#include "cxa_exception.h"
18#include "cxa_handlers.h"
19#include "fallback_malloc.h"
20#include "include/atomic_support.h"
21
22#if __has_feature(address_sanitizer)
23extern "C" void __asan_handle_no_return(void);
24#endif
25
26// +---------------------------+-----------------------------+---------------+
27// | __cxa_exception | _Unwind_Exception CLNGC++\0 | thrown object |
28// +---------------------------+-----------------------------+---------------+
29// ^
30// |
31// +-------------------------------------------------------+
32// |
33// +---------------------------+-----------------------------+
34// | __cxa_dependent_exception | _Unwind_Exception CLNGC++\1 |
35// +---------------------------+-----------------------------+
36
37namespace __cxxabiv1 {
38
39// Utility routines
40static
41inline
42__cxa_exception*
43cxa_exception_from_thrown_object(void* thrown_object)
44{
45 return static_cast<__cxa_exception*>(thrown_object) - 1;
46}
47
48// Note: This is never called when exception_header is masquerading as a
49// __cxa_dependent_exception.
50static
51inline
52void*
53thrown_object_from_cxa_exception(__cxa_exception* exception_header)
54{
55 return static_cast<void*>(exception_header + 1);
56}
57
58// Get the exception object from the unwind pointer.
59// Relies on the structure layout, where the unwind pointer is right in
60// front of the user's exception object
61static
62inline
63__cxa_exception*
64cxa_exception_from_exception_unwind_exception(_Unwind_Exception* unwind_exception)
65{
66 return cxa_exception_from_thrown_object(unwind_exception + 1 );
67}
68
69// Round s up to next multiple of a.
70static inline
71size_t aligned_allocation_size(size_t s, size_t a) {
72 return (s + a - 1) & ~(a - 1);
73}
74
75static inline
76size_t cxa_exception_size_from_exception_thrown_size(size_t size) {
77 return aligned_allocation_size(size + sizeof (__cxa_exception),
78 alignof(__cxa_exception));
79}
80
81void __setExceptionClass(_Unwind_Exception* unwind_exception, uint64_t newValue) {
82 ::memcpy(&unwind_exception->exception_class, &newValue, sizeof(newValue));
83}
84
85
86static void setOurExceptionClass(_Unwind_Exception* unwind_exception) {
87 __setExceptionClass(unwind_exception, kOurExceptionClass);
88}
89
90static void setDependentExceptionClass(_Unwind_Exception* unwind_exception) {
91 __setExceptionClass(unwind_exception, kOurDependentExceptionClass);
92}
93
94// Is it one of ours?
95uint64_t __getExceptionClass(const _Unwind_Exception* unwind_exception) {
96 // On x86 and some ARM unwinders, unwind_exception->exception_class is
97 // a uint64_t. On other ARM unwinders, it is a char[8].
98 // See: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
99 // So we just copy it into a uint64_t to be sure.
100 uint64_t exClass;
101 ::memcpy(&exClass, &unwind_exception->exception_class, sizeof(exClass));
102 return exClass;
103}
104
105bool __isOurExceptionClass(const _Unwind_Exception* unwind_exception) {
106 return (__getExceptionClass(unwind_exception) & get_vendor_and_language) ==
107 (kOurExceptionClass & get_vendor_and_language);
108}
109
110static bool isDependentException(_Unwind_Exception* unwind_exception) {
111 return (__getExceptionClass(unwind_exception) & 0xFF) == 0x01;
112}
113
114// This does not need to be atomic
115static inline int incrementHandlerCount(__cxa_exception *exception) {
116 return ++exception->handlerCount;
117}
118
119// This does not need to be atomic
120static inline int decrementHandlerCount(__cxa_exception *exception) {
121 return --exception->handlerCount;
122}
123
124/*
125 If reason isn't _URC_FOREIGN_EXCEPTION_CAUGHT, then the terminateHandler
126 stored in exc is called. Otherwise the exceptionDestructor stored in
127 exc is called, and then the memory for the exception is deallocated.
128
129 This is never called for a __cxa_dependent_exception.
130*/
131static
132void
133exception_cleanup_func(_Unwind_Reason_Code reason, _Unwind_Exception* unwind_exception)
134{
135 __cxa_exception* exception_header = cxa_exception_from_exception_unwind_exception(unwind_exception);
136 if (_URC_FOREIGN_EXCEPTION_CAUGHT != reason)
137 std::__terminate(exception_header->terminateHandler);
138 // Just in case there exists a dependent exception that is pointing to this,
139 // check the reference count and only destroy this if that count goes to zero.
140 __cxa_decrement_exception_refcount(unwind_exception + 1);
141}
142
143static _LIBCXXABI_NORETURN void failed_throw(__cxa_exception* exception_header) {
144// Section 2.5.3 says:
145// * For purposes of this ABI, several things are considered exception handlers:
146// ** A terminate() call due to a throw.
147// and
148// * Upon entry, Following initialization of the catch parameter,
149// a handler must call:
150// * void *__cxa_begin_catch(void *exceptionObject );
151 (void) __cxa_begin_catch(&exception_header->unwindHeader);
152 std::__terminate(exception_header->terminateHandler);
153}
154
155// Return the offset of the __cxa_exception header from the start of the
156// allocated buffer. If __cxa_exception's alignment is smaller than the maximum
157// useful alignment for the target machine, padding has to be inserted before
158// the header to ensure the thrown object that follows the header is
159// sufficiently aligned. This happens if _Unwind_exception isn't double-word
160// aligned (on Darwin, for example).
161static size_t get_cxa_exception_offset() {
162 struct S {
163 } __attribute__((aligned));
164
165 // Compute the maximum alignment for the target machine.
166 constexpr size_t alignment = alignof(S);
167 constexpr size_t excp_size = sizeof(__cxa_exception);
168 constexpr size_t aligned_size =
169 (excp_size + alignment - 1) / alignment * alignment;
170 constexpr size_t offset = aligned_size - excp_size;
171 static_assert((offset == 0 || alignof(_Unwind_Exception) < alignment),
172 "offset is non-zero only if _Unwind_Exception isn't aligned");
173 return offset;
174}
175
176extern "C" {
177
178// Allocate a __cxa_exception object, and zero-fill it.
179// Reserve "thrown_size" bytes on the end for the user's exception
180// object. Zero-fill the object. If memory can't be allocated, call
181// std::terminate. Return a pointer to the memory to be used for the
182// user's exception object.
183void *__cxa_allocate_exception(size_t thrown_size) throw() {
184 size_t actual_size = cxa_exception_size_from_exception_thrown_size(thrown_size);
185
186 // Allocate extra space before the __cxa_exception header to ensure the
187 // start of the thrown object is sufficiently aligned.
188 size_t header_offset = get_cxa_exception_offset();
189 char *raw_buffer =
190 (char *)__aligned_malloc_with_fallback(header_offset + actual_size);
191 if (NULL == raw_buffer)
192 std::terminate();
193 __cxa_exception *exception_header =
194 static_cast<__cxa_exception *>((void *)(raw_buffer + header_offset));
195 ::memset(exception_header, 0, actual_size);
196 return thrown_object_from_cxa_exception(exception_header);
197}
198
199
200// Free a __cxa_exception object allocated with __cxa_allocate_exception.
201void __cxa_free_exception(void *thrown_object) throw() {
202 // Compute the size of the padding before the header.
203 size_t header_offset = get_cxa_exception_offset();
204 char *raw_buffer =
205 ((char *)cxa_exception_from_thrown_object(thrown_object)) - header_offset;
206 __aligned_free_with_fallback((void *)raw_buffer);
207}
208
209
210// This function shall allocate a __cxa_dependent_exception and
211// return a pointer to it. (Really to the object, not past its' end).
212// Otherwise, it will work like __cxa_allocate_exception.
213void * __cxa_allocate_dependent_exception () {
214 size_t actual_size = sizeof(__cxa_dependent_exception);
215 void *ptr = __aligned_malloc_with_fallback(actual_size);
216 if (NULL == ptr)
217 std::terminate();
218 ::memset(ptr, 0, actual_size);
219 return ptr;
220}
221
222
223// This function shall free a dependent_exception.
224// It does not affect the reference count of the primary exception.
225void __cxa_free_dependent_exception (void * dependent_exception) {
226 __aligned_free_with_fallback(dependent_exception);
227}
228
229
230// 2.4.3 Throwing the Exception Object
231/*
232After constructing the exception object with the throw argument value,
233the generated code calls the __cxa_throw runtime library routine. This
234routine never returns.
235
236The __cxa_throw routine will do the following:
237
238* Obtain the __cxa_exception header from the thrown exception object address,
239which can be computed as follows:
240 __cxa_exception *header = ((__cxa_exception *) thrown_exception - 1);
241* Save the current unexpected_handler and terminate_handler in the __cxa_exception header.
242* Save the tinfo and dest arguments in the __cxa_exception header.
243* Set the exception_class field in the unwind header. This is a 64-bit value
244representing the ASCII string "XXXXC++\0", where "XXXX" is a
245vendor-dependent string. That is, for implementations conforming to this
246ABI, the low-order 4 bytes of this 64-bit value will be "C++\0".
247* Increment the uncaught_exception flag.
248* Call _Unwind_RaiseException in the system unwind library, Its argument is the
249pointer to the thrown exception, which __cxa_throw itself received as an argument.
250__Unwind_RaiseException begins the process of stack unwinding, described
251in Section 2.5. In special cases, such as an inability to find a
252handler, _Unwind_RaiseException may return. In that case, __cxa_throw
253will call terminate, assuming that there was no handler for the
254exception.
255*/
256void
257__cxa_throw(void *thrown_object, std::type_info *tinfo, void (*dest)(void *)) {
258 __cxa_eh_globals *globals = __cxa_get_globals();
259 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
260
261 exception_header->unexpectedHandler = std::get_unexpected();
262 exception_header->terminateHandler = std::get_terminate();
263 exception_header->exceptionType = tinfo;
264 exception_header->exceptionDestructor = dest;
265 setOurExceptionClass(&exception_header->unwindHeader);
266 exception_header->referenceCount = 1; // This is a newly allocated exception, no need for thread safety.
267 globals->uncaughtExceptions += 1; // Not atomically, since globals are thread-local
268
269 exception_header->unwindHeader.exception_cleanup = exception_cleanup_func;
270
271#if __has_feature(address_sanitizer)
272 // Inform the ASan runtime that now might be a good time to clean stuff up.
273 __asan_handle_no_return();
274#endif
275
276#ifdef __USING_SJLJ_EXCEPTIONS__
277 _Unwind_SjLj_RaiseException(&exception_header->unwindHeader);
278#else
279 _Unwind_RaiseException(&exception_header->unwindHeader);
280#endif
281 // This only happens when there is no handler, or some unexpected unwinding
282 // error happens.
283 failed_throw(exception_header);
284}
285
286
287// 2.5.3 Exception Handlers
288/*
289The adjusted pointer is computed by the personality routine during phase 1
290 and saved in the exception header (either __cxa_exception or
291 __cxa_dependent_exception).
292
293 Requires: exception is native
294*/
295void *__cxa_get_exception_ptr(void *unwind_exception) throw() {
296#if defined(_LIBCXXABI_ARM_EHABI)
297 return reinterpret_cast<void*>(
298 static_cast<_Unwind_Control_Block*>(unwind_exception)->barrier_cache.bitpattern[0]);
299#else
300 return cxa_exception_from_exception_unwind_exception(
301 static_cast<_Unwind_Exception*>(unwind_exception))->adjustedPtr;
302#endif
303}
304
305#if defined(_LIBCXXABI_ARM_EHABI)
306/*
307The routine to be called before the cleanup. This will save __cxa_exception in
308__cxa_eh_globals, so that __cxa_end_cleanup() can recover later.
309*/
310bool __cxa_begin_cleanup(void *unwind_arg) throw() {
311 _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(unwind_arg);
312 __cxa_eh_globals* globals = __cxa_get_globals();
313 __cxa_exception* exception_header =
314 cxa_exception_from_exception_unwind_exception(unwind_exception);
315
316 if (__isOurExceptionClass(unwind_exception))
317 {
318 if (0 == exception_header->propagationCount)
319 {
320 exception_header->nextPropagatingException = globals->propagatingExceptions;
321 globals->propagatingExceptions = exception_header;
322 }
323 ++exception_header->propagationCount;
324 }
325 else
326 {
327 // If the propagatingExceptions stack is not empty, since we can't
328 // chain the foreign exception, terminate it.
329 if (NULL != globals->propagatingExceptions)
330 std::terminate();
331 globals->propagatingExceptions = exception_header;
332 }
333 return true;
334}
335
336/*
337The routine to be called after the cleanup has been performed. It will get the
338propagating __cxa_exception from __cxa_eh_globals, and continue the stack
339unwinding with _Unwind_Resume.
340
341According to ARM EHABI 8.4.1, __cxa_end_cleanup() should not clobber any
342register, thus we have to write this function in assembly so that we can save
343{r1, r2, r3}. We don't have to save r0 because it is the return value and the
344first argument to _Unwind_Resume(). In addition, we are saving r4 in order to
345align the stack to 16 bytes, even though it is a callee-save register.
346*/
347__attribute__((used)) static _Unwind_Exception *
348__cxa_end_cleanup_impl()
349{
350 __cxa_eh_globals* globals = __cxa_get_globals();
351 __cxa_exception* exception_header = globals->propagatingExceptions;
352 if (NULL == exception_header)
353 {
354 // It seems that __cxa_begin_cleanup() is not called properly.
355 // We have no choice but terminate the program now.
356 std::terminate();
357 }
358
359 if (__isOurExceptionClass(&exception_header->unwindHeader))
360 {
361 --exception_header->propagationCount;
362 if (0 == exception_header->propagationCount)
363 {
364 globals->propagatingExceptions = exception_header->nextPropagatingException;
365 exception_header->nextPropagatingException = NULL;
366 }
367 }
368 else
369 {
370 globals->propagatingExceptions = NULL;
371 }
372 return &exception_header->unwindHeader;
373}
374
375asm (
376 " .pushsection .text.__cxa_end_cleanup,\"ax\",%progbits\n"
377 " .globl __cxa_end_cleanup\n"
378 " .type __cxa_end_cleanup,%function\n"
379 "__cxa_end_cleanup:\n"
380 " push {r1, r2, r3, r4}\n"
381 " bl __cxa_end_cleanup_impl\n"
382 " pop {r1, r2, r3, r4}\n"
383 " bl _Unwind_Resume\n"
384 " bl abort\n"
385 " .popsection"
386);
387#endif // defined(_LIBCXXABI_ARM_EHABI)
388
389/*
390This routine can catch foreign or native exceptions. If native, the exception
391can be a primary or dependent variety. This routine may remain blissfully
392ignorant of whether the native exception is primary or dependent.
393
394If the exception is native:
395* Increment's the exception's handler count.
396* Push the exception on the stack of currently-caught exceptions if it is not
397 already there (from a rethrow).
398* Decrements the uncaught_exception count.
399* Returns the adjusted pointer to the exception object, which is stored in
400 the __cxa_exception by the personality routine.
401
402If the exception is foreign, this means it did not originate from one of throw
403routines. The foreign exception does not necessarily have a __cxa_exception
404header. However we can catch it here with a catch (...), or with a call
405to terminate or unexpected during unwinding.
406* Do not try to increment the exception's handler count, we don't know where
407 it is.
408* Push the exception on the stack of currently-caught exceptions only if the
409 stack is empty. The foreign exception has no way to link to the current
410 top of stack. If the stack is not empty, call terminate. Even with an
411 empty stack, this is hacked in by pushing a pointer to an imaginary
412 __cxa_exception block in front of the foreign exception. It would be better
413 if the __cxa_eh_globals structure had a stack of _Unwind_Exception, but it
414 doesn't. It has a stack of __cxa_exception (which has a next* in it).
415* Do not decrement the uncaught_exception count because we didn't increment it
416 in __cxa_throw (or one of our rethrow functions).
417* If we haven't terminated, assume the exception object is just past the
418 _Unwind_Exception and return a pointer to that.
419*/
420void*
421__cxa_begin_catch(void* unwind_arg) throw()
422{
423 _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(unwind_arg);
424 bool native_exception = __isOurExceptionClass(unwind_exception);
425 __cxa_eh_globals* globals = __cxa_get_globals();
426 // exception_header is a hackish offset from a foreign exception, but it
427 // works as long as we're careful not to try to access any __cxa_exception
428 // parts.
429 __cxa_exception* exception_header =
430 cxa_exception_from_exception_unwind_exception
431 (
432 static_cast<_Unwind_Exception*>(unwind_exception)
433 );
434 if (native_exception)
435 {
436 // Increment the handler count, removing the flag about being rethrown
437 exception_header->handlerCount = exception_header->handlerCount < 0 ?
438 -exception_header->handlerCount + 1 : exception_header->handlerCount + 1;
439 // place the exception on the top of the stack if it's not already
440 // there by a previous rethrow
441 if (exception_header != globals->caughtExceptions)
442 {
443 exception_header->nextException = globals->caughtExceptions;
444 globals->caughtExceptions = exception_header;
445 }
446 globals->uncaughtExceptions -= 1; // Not atomically, since globals are thread-local
447#if defined(_LIBCXXABI_ARM_EHABI)
448 return reinterpret_cast<void*>(exception_header->unwindHeader.barrier_cache.bitpattern[0]);
449#else
450 return exception_header->adjustedPtr;
451#endif
452 }
453 // Else this is a foreign exception
454 // If the caughtExceptions stack is not empty, terminate
455 if (globals->caughtExceptions != 0)
456 std::terminate();
457 // Push the foreign exception on to the stack
458 globals->caughtExceptions = exception_header;
459 return unwind_exception + 1;
460}
461
462
463/*
464Upon exit for any reason, a handler must call:
465 void __cxa_end_catch ();
466
467This routine can be called for either a native or foreign exception.
468For a native exception:
469* Locates the most recently caught exception and decrements its handler count.
470* Removes the exception from the caught exception stack, if the handler count goes to zero.
471* If the handler count goes down to zero, and the exception was not re-thrown
472 by throw, it locates the primary exception (which may be the same as the one
473 it's handling) and decrements its reference count. If that reference count
474 goes to zero, the function destroys the exception. In any case, if the current
475 exception is a dependent exception, it destroys that.
476
477For a foreign exception:
478* If it has been rethrown, there is nothing to do.
479* Otherwise delete the exception and pop the catch stack to empty.
480*/
481void __cxa_end_catch() {
482 static_assert(sizeof(__cxa_exception) == sizeof(__cxa_dependent_exception),
483 "sizeof(__cxa_exception) must be equal to "
484 "sizeof(__cxa_dependent_exception)");
485 static_assert(__builtin_offsetof(__cxa_exception, referenceCount) ==
486 __builtin_offsetof(__cxa_dependent_exception,
487 primaryException),
488 "the layout of __cxa_exception must match the layout of "
489 "__cxa_dependent_exception");
490 static_assert(__builtin_offsetof(__cxa_exception, handlerCount) ==
491 __builtin_offsetof(__cxa_dependent_exception, handlerCount),
492 "the layout of __cxa_exception must match the layout of "
493 "__cxa_dependent_exception");
494 __cxa_eh_globals* globals = __cxa_get_globals_fast(); // __cxa_get_globals called in __cxa_begin_catch
495 __cxa_exception* exception_header = globals->caughtExceptions;
496 // If we've rethrown a foreign exception, then globals->caughtExceptions
497 // will have been made an empty stack by __cxa_rethrow() and there is
498 // nothing more to be done. Do nothing!
499 if (NULL != exception_header)
500 {
501 bool native_exception = __isOurExceptionClass(&exception_header->unwindHeader);
502 if (native_exception)
503 {
504 // This is a native exception
505 if (exception_header->handlerCount < 0)
506 {
507 // The exception has been rethrown by __cxa_rethrow, so don't delete it
508 if (0 == incrementHandlerCount(exception_header))
509 {
510 // Remove from the chain of uncaught exceptions
511 globals->caughtExceptions = exception_header->nextException;
512 // but don't destroy
513 }
514 // Keep handlerCount negative in case there are nested catch's
515 // that need to be told that this exception is rethrown. Don't
516 // erase this rethrow flag until the exception is recaught.
517 }
518 else
519 {
520 // The native exception has not been rethrown
521 if (0 == decrementHandlerCount(exception_header))
522 {
523 // Remove from the chain of uncaught exceptions
524 globals->caughtExceptions = exception_header->nextException;
525 // Destroy this exception, being careful to distinguish
526 // between dependent and primary exceptions
527 if (isDependentException(&exception_header->unwindHeader))
528 {
529 // Reset exception_header to primaryException and deallocate the dependent exception
530 __cxa_dependent_exception* dep_exception_header =
531 reinterpret_cast<__cxa_dependent_exception*>(exception_header);
532 exception_header =
533 cxa_exception_from_thrown_object(dep_exception_header->primaryException);
534 __cxa_free_dependent_exception(dep_exception_header);
535 }
536 // Destroy the primary exception only if its referenceCount goes to 0
537 // (this decrement must be atomic)
538 __cxa_decrement_exception_refcount(thrown_object_from_cxa_exception(exception_header));
539 }
540 }
541 }
542 else
543 {
544 // The foreign exception has not been rethrown. Pop the stack
545 // and delete it. If there are nested catch's and they try
546 // to touch a foreign exception in any way, that is undefined
547 // behavior. They likely can't since the only way to catch
548 // a foreign exception is with catch (...)!
549 _Unwind_DeleteException(&globals->caughtExceptions->unwindHeader);
550 globals->caughtExceptions = 0;
551 }
552 }
553}
554
555// Note: exception_header may be masquerading as a __cxa_dependent_exception
556// and that's ok. exceptionType is there too.
557// However watch out for foreign exceptions. Return null for them.
558std::type_info *__cxa_current_exception_type() {
559// get the current exception
560 __cxa_eh_globals *globals = __cxa_get_globals_fast();
561 if (NULL == globals)
562 return NULL; // If there have never been any exceptions, there are none now.
563 __cxa_exception *exception_header = globals->caughtExceptions;
564 if (NULL == exception_header)
565 return NULL; // No current exception
566 if (!__isOurExceptionClass(&exception_header->unwindHeader))
567 return NULL;
568 return exception_header->exceptionType;
569}
570
571// 2.5.4 Rethrowing Exceptions
572/* This routine can rethrow native or foreign exceptions.
573If the exception is native:
574* marks the exception object on top of the caughtExceptions stack
575 (in an implementation-defined way) as being rethrown.
576* If the caughtExceptions stack is empty, it calls terminate()
577 (see [C++FDIS] [except.throw], 15.1.8).
578* It then calls _Unwind_RaiseException which should not return
579 (terminate if it does).
580 Note: exception_header may be masquerading as a __cxa_dependent_exception
581 and that's ok.
582*/
583void __cxa_rethrow() {
584 __cxa_eh_globals* globals = __cxa_get_globals();
585 __cxa_exception* exception_header = globals->caughtExceptions;
586 if (NULL == exception_header)
587 std::terminate(); // throw; called outside of a exception handler
588 bool native_exception = __isOurExceptionClass(&exception_header->unwindHeader);
589 if (native_exception)
590 {
591 // Mark the exception as being rethrown (reverse the effects of __cxa_begin_catch)
592 exception_header->handlerCount = -exception_header->handlerCount;
593 globals->uncaughtExceptions += 1;
594 // __cxa_end_catch will remove this exception from the caughtExceptions stack if necessary
595 }
596 else // this is a foreign exception
597 {
598 // The only way to communicate to __cxa_end_catch that we've rethrown
599 // a foreign exception, so don't delete us, is to pop the stack here
600 // which must be empty afterwards. Then __cxa_end_catch will do
601 // nothing
602 globals->caughtExceptions = 0;
603 }
604#ifdef __USING_SJLJ_EXCEPTIONS__
605 _Unwind_SjLj_RaiseException(&exception_header->unwindHeader);
606#else
607 _Unwind_RaiseException(&exception_header->unwindHeader);
608#endif
609
610 // If we get here, some kind of unwinding error has occurred.
611 // There is some weird code generation bug happening with
612 // Apple clang version 4.0 (tags/Apple/clang-418.0.2) (based on LLVM 3.1svn)
613 // If we call failed_throw here. Turns up with -O2 or higher, and -Os.
614 __cxa_begin_catch(&exception_header->unwindHeader);
615 if (native_exception)
616 std::__terminate(exception_header->terminateHandler);
617 // Foreign exception: can't get exception_header->terminateHandler
618 std::terminate();
619}
620
621/*
622 If thrown_object is not null, atomically increment the referenceCount field
623 of the __cxa_exception header associated with the thrown object referred to
624 by thrown_object.
625
626 Requires: If thrown_object is not NULL, it is a native exception.
627*/
628void
629__cxa_increment_exception_refcount(void *thrown_object) throw() {
630 if (thrown_object != NULL )
631 {
632 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
633 std::__libcpp_atomic_add(&exception_header->referenceCount, size_t(1));
634 }
635}
636
637/*
638 If thrown_object is not null, atomically decrement the referenceCount field
639 of the __cxa_exception header associated with the thrown object referred to
640 by thrown_object. If the referenceCount drops to zero, destroy and
641 deallocate the exception.
642
643 Requires: If thrown_object is not NULL, it is a native exception.
644*/
645_LIBCXXABI_NO_CFI
646void __cxa_decrement_exception_refcount(void *thrown_object) throw() {
647 if (thrown_object != NULL )
648 {
649 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
650 if (std::__libcpp_atomic_add(&exception_header->referenceCount, size_t(-1)) == 0)
651 {
652 if (NULL != exception_header->exceptionDestructor)
653 exception_header->exceptionDestructor(thrown_object);
654 __cxa_free_exception(thrown_object);
655 }
656 }
657}
658
659/*
660 Returns a pointer to the thrown object (if any) at the top of the
661 caughtExceptions stack. Atomically increment the exception's referenceCount.
662 If there is no such thrown object or if the thrown object is foreign,
663 returns null.
664
665 We can use __cxa_get_globals_fast here to get the globals because if there have
666 been no exceptions thrown, ever, on this thread, we can return NULL without
667 the need to allocate the exception-handling globals.
668*/
669void *__cxa_current_primary_exception() throw() {
670// get the current exception
671 __cxa_eh_globals* globals = __cxa_get_globals_fast();
672 if (NULL == globals)
673 return NULL; // If there are no globals, there is no exception
674 __cxa_exception* exception_header = globals->caughtExceptions;
675 if (NULL == exception_header)
676 return NULL; // No current exception
677 if (!__isOurExceptionClass(&exception_header->unwindHeader))
678 return NULL; // Can't capture a foreign exception (no way to refcount it)
679 if (isDependentException(&exception_header->unwindHeader)) {
680 __cxa_dependent_exception* dep_exception_header =
681 reinterpret_cast<__cxa_dependent_exception*>(exception_header);
682 exception_header = cxa_exception_from_thrown_object(dep_exception_header->primaryException);
683 }
684 void* thrown_object = thrown_object_from_cxa_exception(exception_header);
685 __cxa_increment_exception_refcount(thrown_object);
686 return thrown_object;
687}
688
689/*
690 If reason isn't _URC_FOREIGN_EXCEPTION_CAUGHT, then the terminateHandler
691 stored in exc is called. Otherwise the referenceCount stored in the
692 primary exception is decremented, destroying the primary if necessary.
693 Finally the dependent exception is destroyed.
694*/
695static
696void
697dependent_exception_cleanup(_Unwind_Reason_Code reason, _Unwind_Exception* unwind_exception)
698{
699 __cxa_dependent_exception* dep_exception_header =
700 reinterpret_cast<__cxa_dependent_exception*>(unwind_exception + 1) - 1;
701 if (_URC_FOREIGN_EXCEPTION_CAUGHT != reason)
702 std::__terminate(dep_exception_header->terminateHandler);
703 __cxa_decrement_exception_refcount(dep_exception_header->primaryException);
704 __cxa_free_dependent_exception(dep_exception_header);
705}
706
707/*
708 If thrown_object is not null, allocate, initialize and throw a dependent
709 exception.
710*/
711void
712__cxa_rethrow_primary_exception(void* thrown_object)
713{
714 if ( thrown_object != NULL )
715 {
716 // thrown_object guaranteed to be native because
717 // __cxa_current_primary_exception returns NULL for foreign exceptions
718 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
719 __cxa_dependent_exception* dep_exception_header =
720 static_cast<__cxa_dependent_exception*>(__cxa_allocate_dependent_exception());
721 dep_exception_header->primaryException = thrown_object;
722 __cxa_increment_exception_refcount(thrown_object);
723 dep_exception_header->exceptionType = exception_header->exceptionType;
724 dep_exception_header->unexpectedHandler = std::get_unexpected();
725 dep_exception_header->terminateHandler = std::get_terminate();
726 setDependentExceptionClass(&dep_exception_header->unwindHeader);
727 __cxa_get_globals()->uncaughtExceptions += 1;
728 dep_exception_header->unwindHeader.exception_cleanup = dependent_exception_cleanup;
729#ifdef __USING_SJLJ_EXCEPTIONS__
730 _Unwind_SjLj_RaiseException(&dep_exception_header->unwindHeader);
731#else
732 _Unwind_RaiseException(&dep_exception_header->unwindHeader);
733#endif
734 // Some sort of unwinding error. Note that terminate is a handler.
735 __cxa_begin_catch(&dep_exception_header->unwindHeader);
736 }
737 // If we return client will call terminate()
738}
739
740bool
741__cxa_uncaught_exception() throw() { return __cxa_uncaught_exceptions() != 0; }
742
743unsigned int
744__cxa_uncaught_exceptions() throw()
745{
746 // This does not report foreign exceptions in flight
747 __cxa_eh_globals* globals = __cxa_get_globals_fast();
748 if (globals == 0)
749 return 0;
750 return globals->uncaughtExceptions;
751}
752
753} // extern "C"
754
755} // abi
756