2 * Copyright 2010-2011 PathScale, Inc. All rights reserved.
3 * Copyright 2021 David Chisnall. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
8 * 1. Redistributions of source code must retain the above copyright notice,
9 * this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
16 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
17 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
18 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
19 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 #pragma weak pthread_key_create
40 #pragma weak pthread_setspecific
41 #pragma weak pthread_getspecific
42 #pragma weak pthread_once
43 #ifdef LIBCXXRT_WEAK_LOCKS
44 #pragma weak pthread_mutex_lock
45 #define pthread_mutex_lock(mtx) do {\
46 if (pthread_mutex_lock) pthread_mutex_lock(mtx);\
48 #pragma weak pthread_mutex_unlock
49 #define pthread_mutex_unlock(mtx) do {\
50 if (pthread_mutex_unlock) pthread_mutex_unlock(mtx);\
52 #pragma weak pthread_cond_signal
53 #define pthread_cond_signal(cv) do {\
54 if (pthread_cond_signal) pthread_cond_signal(cv);\
56 #pragma weak pthread_cond_wait
57 #define pthread_cond_wait(cv, mtx) do {\
58 if (pthread_cond_wait) pthread_cond_wait(cv, mtx);\
62 using namespace ABI_NAMESPACE;
65 * Saves the result of the landing pad that we have found. For ARM, this is
66 * stored in the generic unwind structure, while on other platforms it is
67 * stored in the C++ exception.
69 static void saveLandingPad(struct _Unwind_Context *context,
70 struct _Unwind_Exception *ucb,
71 struct __cxa_exception *ex,
73 dw_eh_ptr_t landingPad)
75 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
76 // On ARM, we store the saved exception in the generic part of the structure
77 ucb->barrier_cache.sp = _Unwind_GetGR(context, 13);
78 ucb->barrier_cache.bitpattern[1] = static_cast<uint32_t>(selector);
79 ucb->barrier_cache.bitpattern[3] = reinterpret_cast<uint32_t>(landingPad);
81 // Cache the results for the phase 2 unwind, if we found a handler
82 // and this is not a foreign exception.
85 ex->handlerSwitchValue = selector;
86 ex->catchTemp = landingPad;
91 * Loads the saved landing pad. Returns 1 on success, 0 on failure.
93 static int loadLandingPad(struct _Unwind_Context *context,
94 struct _Unwind_Exception *ucb,
95 struct __cxa_exception *ex,
96 unsigned long *selector,
97 dw_eh_ptr_t *landingPad)
99 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
100 *selector = ucb->barrier_cache.bitpattern[1];
101 *landingPad = reinterpret_cast<dw_eh_ptr_t>(ucb->barrier_cache.bitpattern[3]);
106 *selector = ex->handlerSwitchValue;
107 *landingPad = reinterpret_cast<dw_eh_ptr_t>(ex->catchTemp);
114 static inline _Unwind_Reason_Code continueUnwinding(struct _Unwind_Exception *ex,
115 struct _Unwind_Context *context)
117 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
118 if (__gnu_unwind_frame(ex, context) != _URC_OK) { return _URC_FAILURE; }
120 return _URC_CONTINUE_UNWIND;
124 extern "C" void __cxa_free_exception(void *thrown_exception);
125 extern "C" void __cxa_free_dependent_exception(void *thrown_exception);
126 extern "C" void* __dynamic_cast(const void *sub,
127 const __class_type_info *src,
128 const __class_type_info *dst,
129 ptrdiff_t src2dst_offset);
132 * The type of a handler that has been found.
139 * A cleanup - the exception will propagate through this frame, but code
140 * must be run when this happens.
144 * A catch statement. The exception will not propagate past this frame
145 * (without an explicit rethrow).
151 * Per-thread info required by the runtime. We store a single structure
152 * pointer in thread-local storage, because this tends to be a scarce resource
153 * and it's impolite to steal all of it and not leave any for the rest of the
156 * Instances of this structure are allocated lazily - at most one per thread -
157 * and are destroyed on thread termination.
159 struct __cxa_thread_info
161 /** The termination handler for this thread. */
162 terminate_handler terminateHandler;
163 /** The unexpected exception handler for this thread. */
164 unexpected_handler unexpectedHandler;
165 #ifndef LIBCXXRT_NO_EMERGENCY_MALLOC
167 * The number of emergency buffers held by this thread. This is 0 in
168 * normal operation - the emergency buffers are only used when malloc()
169 * fails to return memory for allocating an exception. Threads are not
170 * permitted to hold more than 4 emergency buffers (as per recommendation
171 * in ABI spec [3.3.1]).
173 int emergencyBuffersHeld;
176 * The exception currently running in a cleanup.
178 _Unwind_Exception *currentCleanup;
180 * Our state with respect to foreign exceptions. Usually none, set to
181 * caught if we have just caught an exception and rethrown if we are
189 } foreign_exception_state;
191 * The public part of this structure, accessible from outside of this
194 __cxa_eh_globals globals;
197 * Dependent exception. This
199 struct __cxa_dependent_exception
203 void *primaryException;
205 std::type_info *exceptionType;
206 void (*exceptionDestructor) (void *);
207 unexpected_handler unexpectedHandler;
208 terminate_handler terminateHandler;
209 __cxa_exception *nextException;
211 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
212 _Unwind_Exception *nextCleanup;
215 int handlerSwitchValue;
216 const char *actionRecord;
217 const char *languageSpecificData;
221 void *primaryException;
223 _Unwind_Exception unwindHeader;
225 static_assert(sizeof(__cxa_exception) == sizeof(__cxa_dependent_exception),
226 "__cxa_exception and __cxa_dependent_exception should have the same size");
227 static_assert(offsetof(__cxa_exception, referenceCount) ==
228 offsetof(__cxa_dependent_exception, primaryException),
229 "referenceCount and primaryException should have the same offset");
230 static_assert(offsetof(__cxa_exception, unwindHeader) ==
231 offsetof(__cxa_dependent_exception, unwindHeader),
232 "unwindHeader fields should have the same offset");
233 static_assert(offsetof(__cxa_dependent_exception, unwindHeader) ==
234 offsetof(__cxa_dependent_exception, adjustedPtr) + 8,
235 "there should be no padding before unwindHeader");
244 virtual ~exception() throw();
245 virtual const char* what() const throw();
251 * Class of exceptions to distinguish between this and other exception types.
253 * The first four characters are the vendor ID. Currently, we use GNUC,
254 * because we aim for ABI-compatibility with the GNU implementation, and
255 * various checks may test for equality of the class, which is incorrect.
257 static const uint64_t exception_class =
258 EXCEPTION_CLASS('G', 'N', 'U', 'C', 'C', '+', '+', '\0');
260 * Class used for dependent exceptions.
262 static const uint64_t dependent_exception_class =
263 EXCEPTION_CLASS('G', 'N', 'U', 'C', 'C', '+', '+', '\x01');
265 * The low four bytes of the exception class, indicating that we conform to the
266 * Itanium C++ ABI. This is currently unused, but should be used in the future
267 * if we change our exception class, to allow this library and libsupc++ to be
268 * linked to the same executable and both to interoperate.
270 static const uint32_t abi_exception_class =
271 GENERIC_EXCEPTION_CLASS('C', '+', '+', '\0');
273 static bool isCXXException(uint64_t cls)
275 return (cls == exception_class) || (cls == dependent_exception_class);
278 static bool isDependentException(uint64_t cls)
280 return cls == dependent_exception_class;
283 static __cxa_exception *exceptionFromPointer(void *ex)
285 return reinterpret_cast<__cxa_exception*>(static_cast<char*>(ex) -
286 offsetof(struct __cxa_exception, unwindHeader));
288 static __cxa_exception *realExceptionFromException(__cxa_exception *ex)
290 if (!isDependentException(ex->unwindHeader.exception_class)) { return ex; }
291 return reinterpret_cast<__cxa_exception*>((reinterpret_cast<__cxa_dependent_exception*>(ex))->primaryException)-1;
297 // Forward declaration of standard library terminate() function used to
299 void terminate(void);
302 using namespace ABI_NAMESPACE;
306 /** The global termination handler. */
307 static atomic<terminate_handler> terminateHandler = abort;
308 /** The global unexpected exception handler. */
309 static atomic<unexpected_handler> unexpectedHandler = std::terminate;
311 /** Key used for thread-local data. */
312 static pthread_key_t eh_key;
316 * Cleanup function, allowing foreign exception handlers to correctly destroy
317 * this exception if they catch it.
319 static void exception_cleanup(_Unwind_Reason_Code reason,
320 struct _Unwind_Exception *ex)
323 // [__cxa_exception [_Unwind_Exception]] [exception object]
325 // __cxa_free_exception expects a pointer to the exception object
326 __cxa_free_exception(static_cast<void*>(ex + 1));
328 static void dependent_exception_cleanup(_Unwind_Reason_Code reason,
329 struct _Unwind_Exception *ex)
332 __cxa_free_dependent_exception(static_cast<void*>(ex + 1));
336 * Recursively walk a list of exceptions and delete them all in post-order.
338 static void free_exception_list(__cxa_exception *ex)
340 if (0 != ex->nextException)
342 free_exception_list(ex->nextException);
344 // __cxa_free_exception() expects to be passed the thrown object, which
345 // immediately follows the exception, not the exception itself
346 __cxa_free_exception(ex+1);
350 * Cleanup function called when a thread exists to make certain that all of the
351 * per-thread data is deleted.
353 static void thread_cleanup(void* thread_info)
355 __cxa_thread_info *info = static_cast<__cxa_thread_info*>(thread_info);
356 if (info->globals.caughtExceptions)
358 // If this is a foreign exception, ask it to clean itself up.
359 if (info->foreign_exception_state != __cxa_thread_info::none)
361 _Unwind_Exception *e = reinterpret_cast<_Unwind_Exception*>(info->globals.caughtExceptions);
362 if (e->exception_cleanup)
363 e->exception_cleanup(_URC_FOREIGN_EXCEPTION_CAUGHT, e);
367 free_exception_list(info->globals.caughtExceptions);
375 * Once control used to protect the key creation.
377 static pthread_once_t once_control = PTHREAD_ONCE_INIT;
380 * We may not be linked against a full pthread implementation. If we're not,
381 * then we need to fake the thread-local storage by storing 'thread-local'
382 * things in a global.
386 * Thread-local storage for a single-threaded program.
388 static __cxa_thread_info singleThreadInfo;
392 static void init_key(void)
394 if ((0 == pthread_key_create) ||
395 (0 == pthread_setspecific) ||
396 (0 == pthread_getspecific))
401 pthread_key_create(&eh_key, thread_cleanup);
402 pthread_setspecific(eh_key, reinterpret_cast<void *>(0x42));
403 fakeTLS = (pthread_getspecific(eh_key) != reinterpret_cast<void *>(0x42));
404 pthread_setspecific(eh_key, 0);
408 * Returns the thread info structure, creating it if it is not already created.
410 static __cxa_thread_info *thread_info()
412 if ((0 == pthread_once) || pthread_once(&once_control, init_key))
416 if (fakeTLS) { return &singleThreadInfo; }
417 __cxa_thread_info *info = static_cast<__cxa_thread_info*>(pthread_getspecific(eh_key));
420 info = static_cast<__cxa_thread_info*>(calloc(1, sizeof(__cxa_thread_info)));
421 pthread_setspecific(eh_key, info);
426 * Fast version of thread_info(). May fail if thread_info() is not called on
427 * this thread at least once already.
429 static __cxa_thread_info *thread_info_fast()
431 if (fakeTLS) { return &singleThreadInfo; }
432 return static_cast<__cxa_thread_info*>(pthread_getspecific(eh_key));
435 * ABI function returning the __cxa_eh_globals structure.
437 extern "C" __cxa_eh_globals *ABI_NAMESPACE::__cxa_get_globals(void)
439 return &(thread_info()->globals);
442 * Version of __cxa_get_globals() assuming that __cxa_get_globals() has already
443 * been called at least once by this thread.
445 extern "C" __cxa_eh_globals *ABI_NAMESPACE::__cxa_get_globals_fast(void)
447 return &(thread_info_fast()->globals);
450 #ifdef LIBCXXRT_NO_EMERGENCY_MALLOC
451 static char *alloc_or_die(size_t size)
453 char *buffer = static_cast<char*>(calloc(1, size));
455 if (buffer == nullptr)
457 fputs("Out of memory attempting to allocate exception\n", stderr);
462 static void free_exception(char *e)
468 * An emergency allocation reserved for when malloc fails. This is treated as
469 * 16 buffers of 1KB each.
471 static char emergency_buffer[16384];
473 * Flag indicating whether each buffer is allocated.
475 static bool buffer_allocated[16];
477 * Lock used to protect emergency allocation.
479 static pthread_mutex_t emergency_malloc_lock = PTHREAD_MUTEX_INITIALIZER;
481 * Condition variable used to wait when two threads are both trying to use the
482 * emergency malloc() buffer at once.
484 static pthread_cond_t emergency_malloc_wait = PTHREAD_COND_INITIALIZER;
487 * Allocates size bytes from the emergency allocation mechanism, if possible.
488 * This function will fail if size is over 1KB or if this thread already has 4
489 * emergency buffers. If all emergency buffers are allocated, it will sleep
490 * until one becomes available.
492 static char *emergency_malloc(size_t size)
494 if (size > 1024) { return 0; }
496 __cxa_thread_info *info = thread_info();
497 // Only 4 emergency buffers allowed per thread!
498 if (info->emergencyBuffersHeld > 3) { return 0; }
500 pthread_mutex_lock(&emergency_malloc_lock);
504 // While we were sleeping on the lock, another thread might have free'd
505 // enough memory for us to use, so try the allocation again - no point
506 // using the emergency buffer if there is some real memory that we can
508 void *m = calloc(1, size);
511 pthread_mutex_unlock(&emergency_malloc_lock);
512 return static_cast<char*>(m);
514 for (int i=0 ; i<16 ; i++)
516 if (!buffer_allocated[i])
519 buffer_allocated[i] = true;
523 // If there still isn't a buffer available, then sleep on the condition
524 // variable. This will be signalled when another thread releases one
525 // of the emergency buffers.
528 pthread_cond_wait(&emergency_malloc_wait, &emergency_malloc_lock);
531 pthread_mutex_unlock(&emergency_malloc_lock);
532 info->emergencyBuffersHeld++;
533 return emergency_buffer + (1024 * buffer);
537 * Frees a buffer returned by emergency_malloc().
539 * Note: Neither this nor emergency_malloc() is particularly efficient. This
540 * should not matter, because neither will be called in normal operation - they
541 * are only used when the program runs out of memory, which should not happen
544 static void emergency_malloc_free(char *ptr)
547 // Find the buffer corresponding to this pointer.
548 for (int i=0 ; i<16 ; i++)
550 if (ptr == static_cast<void*>(emergency_buffer + (1024 * i)))
556 assert(buffer >= 0 &&
557 "Trying to free something that is not an emergency buffer!");
558 // emergency_malloc() is expected to return 0-initialized data. We don't
559 // zero the buffer when allocating it, because the static buffers will
560 // begin life containing 0 values.
561 memset(ptr, 0, 1024);
562 // Signal the condition variable to wake up any threads that are blocking
563 // waiting for some space in the emergency buffer
564 pthread_mutex_lock(&emergency_malloc_lock);
565 // In theory, we don't need to do this with the lock held. In practice,
566 // our array of bools will probably be updated using 32-bit or 64-bit
567 // memory operations, so this update may clobber adjacent values.
568 buffer_allocated[buffer] = false;
569 pthread_cond_signal(&emergency_malloc_wait);
570 pthread_mutex_unlock(&emergency_malloc_lock);
573 static char *alloc_or_die(size_t size)
575 char *buffer = static_cast<char*>(calloc(1, size));
577 // If calloc() doesn't want to give us any memory, try using an emergency
581 buffer = emergency_malloc(size);
582 // This is only reached if the allocation is greater than 1KB, and
583 // anyone throwing objects that big really should know better.
586 fprintf(stderr, "Out of memory attempting to allocate exception\n");
592 static void free_exception(char *e)
594 // If this allocation is within the address range of the emergency buffer,
595 // don't call free() because it was not allocated with malloc()
596 if ((e >= emergency_buffer) &&
597 (e < (emergency_buffer + sizeof(emergency_buffer))))
599 emergency_malloc_free(e);
609 * Allocates an exception structure. Returns a pointer to the space that can
610 * be used to store an object of thrown_size bytes. This function will use an
611 * emergency buffer if malloc() fails, and may block if there are no such
614 extern "C" void *__cxa_allocate_exception(size_t thrown_size)
616 size_t size = thrown_size + sizeof(__cxa_exception);
617 char *buffer = alloc_or_die(size);
618 return buffer+sizeof(__cxa_exception);
621 extern "C" void *__cxa_allocate_dependent_exception(void)
623 size_t size = sizeof(__cxa_dependent_exception);
624 char *buffer = alloc_or_die(size);
625 return buffer+sizeof(__cxa_dependent_exception);
629 * __cxa_free_exception() is called when an exception was thrown in between
630 * calling __cxa_allocate_exception() and actually throwing the exception.
631 * This happens when the object's copy constructor throws an exception.
633 * In this implementation, it is also called by __cxa_end_catch() and during
636 extern "C" void __cxa_free_exception(void *thrown_exception)
638 __cxa_exception *ex = reinterpret_cast<__cxa_exception*>(thrown_exception) - 1;
639 // Free the object that was thrown, calling its destructor
640 if (0 != ex->exceptionDestructor)
644 ex->exceptionDestructor(thrown_exception);
648 // FIXME: Check that this is really what the spec says to do.
653 free_exception(reinterpret_cast<char*>(ex));
656 static void releaseException(__cxa_exception *exception)
658 if (isDependentException(exception->unwindHeader.exception_class))
660 __cxa_free_dependent_exception(exception+1);
663 if (__sync_sub_and_fetch(&exception->referenceCount, 1) == 0)
665 // __cxa_free_exception() expects to be passed the thrown object,
666 // which immediately follows the exception, not the exception
668 __cxa_free_exception(exception+1);
672 void __cxa_free_dependent_exception(void *thrown_exception)
674 __cxa_dependent_exception *ex = reinterpret_cast<__cxa_dependent_exception*>(thrown_exception) - 1;
675 assert(isDependentException(ex->unwindHeader.exception_class));
676 if (ex->primaryException)
678 releaseException(realExceptionFromException(reinterpret_cast<__cxa_exception*>(ex)));
680 free_exception(reinterpret_cast<char*>(ex));
684 * Callback function used with _Unwind_Backtrace().
686 * Prints a stack trace. Used only for debugging help.
688 * Note: As of FreeBSD 8.1, dladd() still doesn't work properly, so this only
689 * correctly prints function names from public, relocatable, symbols.
691 static _Unwind_Reason_Code trace(struct _Unwind_Context *context, void *c)
695 dladdr(reinterpret_cast<void *>(__cxa_current_exception_type), &myinfo);
696 void *ip = reinterpret_cast<void*>(_Unwind_GetIP(context));
698 if (dladdr(ip, &info) != 0)
700 if (mylookup == 0 || strcmp(info.dli_fname, myinfo.dli_fname) != 0)
702 printf("%p:%s() in %s\n", ip, info.dli_sname, info.dli_fname);
705 return _URC_CONTINUE_UNWIND;
709 * Report a failure that occurred when attempting to throw an exception.
711 * If the failure happened by falling off the end of the stack without finding
712 * a handler, prints a back trace before aborting.
714 #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
715 extern "C" void *__cxa_begin_catch(void *e) throw();
717 extern "C" void *__cxa_begin_catch(void *e);
719 static void report_failure(_Unwind_Reason_Code err, __cxa_exception *thrown_exception)
724 case _URC_FATAL_PHASE1_ERROR:
725 fprintf(stderr, "Fatal error during phase 1 unwinding\n");
727 #if !defined(__arm__) || defined(__ARM_DWARF_EH__)
728 case _URC_FATAL_PHASE2_ERROR:
729 fprintf(stderr, "Fatal error during phase 2 unwinding\n");
732 case _URC_END_OF_STACK:
733 __cxa_begin_catch (&(thrown_exception->unwindHeader));
735 fprintf(stderr, "Terminating due to uncaught exception %p",
736 static_cast<void*>(thrown_exception));
737 thrown_exception = realExceptionFromException(thrown_exception);
738 static const __class_type_info *e_ti =
739 static_cast<const __class_type_info*>(&typeid(std::exception));
740 const __class_type_info *throw_ti =
741 dynamic_cast<const __class_type_info*>(thrown_exception->exceptionType);
745 static_cast<std::exception*>(e_ti->cast_to(static_cast<void*>(thrown_exception+1),
749 fprintf(stderr, " '%s'", e->what());
753 size_t bufferSize = 128;
754 char *demangled = static_cast<char*>(malloc(bufferSize));
755 const char *mangled = thrown_exception->exceptionType->name();
757 demangled = __cxa_demangle(mangled, demangled, &bufferSize, &status);
758 fprintf(stderr, " of type %s\n",
759 status == 0 ? demangled : mangled);
760 if (status == 0) { free(demangled); }
761 // Print a back trace if no handler is found.
762 // TODO: Make this optional
763 _Unwind_Backtrace(trace, 0);
765 // Just abort. No need to call std::terminate for the second time
772 static void throw_exception(__cxa_exception *ex)
774 __cxa_thread_info *info = thread_info();
775 ex->unexpectedHandler = info->unexpectedHandler;
776 if (0 == ex->unexpectedHandler)
778 ex->unexpectedHandler = unexpectedHandler.load();
780 ex->terminateHandler = info->terminateHandler;
781 if (0 == ex->terminateHandler)
783 ex->terminateHandler = terminateHandler.load();
785 info->globals.uncaughtExceptions++;
787 _Unwind_Reason_Code err = _Unwind_RaiseException(&ex->unwindHeader);
788 // The _Unwind_RaiseException() function should not return, it should
789 // unwind the stack past this function. If it does return, then something
791 report_failure(err, ex);
794 extern "C" __cxa_exception *__cxa_init_primary_exception(
795 void *object, std::type_info* tinfo, void (*dest)(void *)) {
796 __cxa_exception *ex = reinterpret_cast<__cxa_exception*>(object) - 1;
798 ex->referenceCount = 0;
799 ex->exceptionType = tinfo;
801 ex->exceptionDestructor = dest;
803 ex->unwindHeader.exception_class = exception_class;
804 ex->unwindHeader.exception_cleanup = exception_cleanup;
811 * ABI function for throwing an exception. Takes the object to be thrown (the
812 * pointer returned by __cxa_allocate_exception()), the type info for the
813 * pointee, and the destructor (if there is one) as arguments.
815 extern "C" void __cxa_throw(void *thrown_exception,
816 std::type_info *tinfo,
819 __cxa_exception *ex = __cxa_init_primary_exception(thrown_exception, tinfo, dest);
820 ex->referenceCount = 1;
825 extern "C" void __cxa_rethrow_primary_exception(void* thrown_exception)
827 if (NULL == thrown_exception) { return; }
829 __cxa_exception *original = exceptionFromPointer(thrown_exception);
830 __cxa_dependent_exception *ex = reinterpret_cast<__cxa_dependent_exception*>(__cxa_allocate_dependent_exception())-1;
832 ex->primaryException = thrown_exception;
833 __cxa_increment_exception_refcount(thrown_exception);
835 ex->exceptionType = original->exceptionType;
836 ex->unwindHeader.exception_class = dependent_exception_class;
837 ex->unwindHeader.exception_cleanup = dependent_exception_cleanup;
839 throw_exception(reinterpret_cast<__cxa_exception*>(ex));
842 extern "C" void *__cxa_current_primary_exception(void)
844 __cxa_eh_globals* globals = __cxa_get_globals();
845 __cxa_exception *ex = globals->caughtExceptions;
847 if (0 == ex) { return NULL; }
848 ex = realExceptionFromException(ex);
849 __sync_fetch_and_add(&ex->referenceCount, 1);
853 extern "C" void __cxa_increment_exception_refcount(void* thrown_exception)
855 if (NULL == thrown_exception) { return; }
856 __cxa_exception *ex = static_cast<__cxa_exception*>(thrown_exception) - 1;
857 if (isDependentException(ex->unwindHeader.exception_class)) { return; }
858 __sync_fetch_and_add(&ex->referenceCount, 1);
860 extern "C" void __cxa_decrement_exception_refcount(void* thrown_exception)
862 if (NULL == thrown_exception) { return; }
863 __cxa_exception *ex = static_cast<__cxa_exception*>(thrown_exception) - 1;
864 releaseException(ex);
868 * ABI function. Rethrows the current exception. Does not remove the
869 * exception from the stack or decrement its handler count - the compiler is
870 * expected to set the landing pad for this function to the end of the catch
871 * block, and then call _Unwind_Resume() to continue unwinding once
872 * __cxa_end_catch() has been called and any cleanup code has been run.
874 extern "C" void __cxa_rethrow()
876 __cxa_thread_info *ti = thread_info();
877 __cxa_eh_globals *globals = &ti->globals;
878 // Note: We don't remove this from the caught list here, because
879 // __cxa_end_catch will be called when we unwind out of the try block. We
880 // could probably make this faster by providing an alternative rethrow
881 // function and ensuring that all cleanup code is run before calling it, so
882 // we can skip the top stack frame when unwinding.
883 __cxa_exception *ex = globals->caughtExceptions;
888 "Attempting to rethrow an exception that doesn't exist!\n");
892 if (ti->foreign_exception_state != __cxa_thread_info::none)
894 ti->foreign_exception_state = __cxa_thread_info::rethrown;
895 _Unwind_Exception *e = reinterpret_cast<_Unwind_Exception*>(ex);
896 _Unwind_Reason_Code err = _Unwind_Resume_or_Rethrow(e);
897 report_failure(err, ex);
901 assert(ex->handlerCount > 0 && "Rethrowing uncaught exception!");
903 // `globals->uncaughtExceptions` was decremented by `__cxa_begin_catch`.
904 // It's normally incremented by `throw_exception`, but this path invokes
905 // `_Unwind_Resume_or_Rethrow` directly to rethrow the exception.
906 // This path is only reachable if we're rethrowing a C++ exception -
907 // foreign exceptions don't adjust any of this state.
908 globals->uncaughtExceptions++;
910 // ex->handlerCount will be decremented in __cxa_end_catch in enclosing
913 // Make handler count negative. This will tell __cxa_end_catch that
914 // exception was rethrown and exception object should not be destroyed
915 // when handler count become zero
916 ex->handlerCount = -ex->handlerCount;
918 // Continue unwinding the stack with this exception. This should unwind to
919 // the place in the caller where __cxa_end_catch() is called. The caller
920 // will then run cleanup code and bounce the exception back with
922 _Unwind_Reason_Code err = _Unwind_Resume_or_Rethrow(&ex->unwindHeader);
923 report_failure(err, ex);
927 * Returns the type_info object corresponding to the filter.
929 static std::type_info *get_type_info_entry(_Unwind_Context *context,
933 // Get the address of the record in the table.
934 dw_eh_ptr_t record = lsda->type_table -
935 dwarf_size_of_fixed_size_field(lsda->type_table_encoding)*filter;
937 dw_eh_ptr_t start = record;
938 // Read the value, but it's probably an indirect reference...
939 int64_t offset = read_value(lsda->type_table_encoding, &record);
941 // (If the entry is 0, don't try to dereference it. That would be bad.)
942 if (offset == 0) { return 0; }
944 // ...so we need to resolve it
945 return reinterpret_cast<std::type_info*>(resolve_indirect_value(context,
946 lsda->type_table_encoding, offset, start));
952 * Checks the type signature found in a handler against the type of the thrown
953 * object. If ex is 0 then it is assumed to be a foreign exception and only
956 static bool check_type_signature(__cxa_exception *ex,
957 const std::type_info *type,
960 void *exception_ptr = static_cast<void*>(ex+1);
961 const std::type_info *ex_type = ex ? ex->exceptionType : 0;
963 bool is_ptr = ex ? ex_type->__is_pointer_p() : false;
966 exception_ptr = *static_cast<void**>(exception_ptr);
968 // Always match a catchall, even with a foreign exception
970 // Note: A 0 here is a catchall, not a cleanup, so we return true to
971 // indicate that we found a catch.
976 adjustedPtr = exception_ptr;
981 if (0 == ex) { return false; }
983 // If the types are the same, no casting is needed.
984 if (*type == *ex_type)
986 adjustedPtr = exception_ptr;
991 if (type->__do_catch(ex_type, &exception_ptr, 1))
993 adjustedPtr = exception_ptr;
1000 * Checks whether the exception matches the type specifiers in this action
1001 * record. If the exception only matches cleanups, then this returns false.
1002 * If it matches a catch (including a catchall) then it returns true.
1004 * The selector argument is used to return the selector that is passed in the
1005 * second exception register when installing the context.
1007 static handler_type check_action_record(_Unwind_Context *context,
1008 dwarf_eh_lsda *lsda,
1009 dw_eh_ptr_t action_record,
1010 __cxa_exception *ex,
1011 unsigned long *selector,
1014 if (!action_record) { return handler_cleanup; }
1015 handler_type found = handler_none;
1016 while (action_record)
1018 int filter = read_sleb128(&action_record);
1019 dw_eh_ptr_t action_record_offset_base = action_record;
1020 int displacement = read_sleb128(&action_record);
1021 action_record = displacement ?
1022 action_record_offset_base + displacement : 0;
1023 // We only check handler types for C++ exceptions - foreign exceptions
1024 // are only allowed for cleanups and catchalls.
1027 std::type_info *handler_type = get_type_info_entry(context, lsda, filter);
1028 if (check_type_signature(ex, handler_type, adjustedPtr))
1031 return handler_catch;
1034 else if (filter < 0 && 0 != ex)
1036 bool matched = false;
1038 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
1040 std::type_info *handler_type = get_type_info_entry(context, lsda, filter--);
1041 while (handler_type)
1043 if (check_type_signature(ex, handler_type, adjustedPtr))
1048 handler_type = get_type_info_entry(context, lsda, filter--);
1051 unsigned char *type_index = reinterpret_cast<unsigned char*>(lsda->type_table) - filter - 1;
1054 std::type_info *handler_type = get_type_info_entry(context, lsda, *(type_index++));
1055 // If the exception spec matches a permitted throw type for
1056 // this function, don't report a handler - we are allowed to
1057 // propagate this exception out.
1058 if (check_type_signature(ex, handler_type, adjustedPtr))
1065 if (matched) { continue; }
1066 // If we don't find an allowed exception spec, we need to install
1067 // the context for this action. The landing pad will then call the
1068 // unexpected exception function. Treat this as a catch
1069 return handler_catch;
1071 else if (filter == 0)
1074 found = handler_cleanup;
1080 static void pushCleanupException(_Unwind_Exception *exceptionObject,
1081 __cxa_exception *ex)
1083 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
1084 __cxa_thread_info *info = thread_info_fast();
1088 if (ex->cleanupCount > 1)
1090 assert(exceptionObject == info->currentCleanup);
1093 ex->nextCleanup = info->currentCleanup;
1095 info->currentCleanup = exceptionObject;
1100 * The exception personality function. This is referenced in the unwinding
1101 * DWARF metadata and is called by the unwind library for each C++ stack frame
1102 * containing catch or cleanup code.
1105 BEGIN_PERSONALITY_FUNCTION(__gxx_personality_v0)
1106 // This personality function is for version 1 of the ABI. If you use it
1107 // with a future version of the ABI, it won't know what to do, so it
1108 // reports a fatal error and give up before it breaks anything.
1111 return _URC_FATAL_PHASE1_ERROR;
1113 __cxa_exception *ex = 0;
1114 __cxa_exception *realEx = 0;
1116 // If this exception is throw by something else then we can't make any
1117 // assumptions about its layout beyond the fields declared in
1118 // _Unwind_Exception.
1119 bool foreignException = !isCXXException(exceptionClass);
1121 // If this isn't a foreign exception, then we have a C++ exception structure
1122 if (!foreignException)
1124 ex = exceptionFromPointer(exceptionObject);
1125 realEx = realExceptionFromException(ex);
1128 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
1129 unsigned char *lsda_addr =
1130 static_cast<unsigned char*>(_Unwind_GetLanguageSpecificData(context));
1132 unsigned char *lsda_addr =
1133 reinterpret_cast<unsigned char*>(static_cast<uintptr_t>(_Unwind_GetLanguageSpecificData(context)));
1136 // No LSDA implies no landing pads - try the next frame
1137 if (0 == lsda_addr) { return continueUnwinding(exceptionObject, context); }
1139 // These two variables define how the exception will be handled.
1140 dwarf_eh_action action = {0};
1141 unsigned long selector = 0;
1143 // During the search phase, we do a complete lookup. If we return
1144 // _URC_HANDLER_FOUND, then the phase 2 unwind will call this function with
1145 // a _UA_HANDLER_FRAME action, telling us to install the handler frame. If
1146 // we return _URC_CONTINUE_UNWIND, we may be called again later with a
1147 // _UA_CLEANUP_PHASE action for this frame.
1149 // The point of the two-stage unwind allows us to entirely avoid any stack
1150 // unwinding if there is no handler. If there are just cleanups found,
1151 // then we can just panic call an abort function.
1153 // Matching a handler is much more expensive than matching a cleanup,
1154 // because we don't need to bother doing type comparisons (or looking at
1155 // the type table at all) for a cleanup. This means that there is no need
1156 // to cache the result of finding a cleanup, because it's (quite) quick to
1157 // look it up again from the action table.
1158 if (actions & _UA_SEARCH_PHASE)
1160 struct dwarf_eh_lsda lsda = parse_lsda(context, lsda_addr);
1162 if (!dwarf_eh_find_callsite(context, &lsda, &action))
1164 // EH range not found. This happens if exception is thrown and not
1165 // caught inside a cleanup (destructor). We should call
1166 // terminate() in this case. The catchTemp (landing pad) field of
1167 // exception object will contain null when personality function is
1168 // called with _UA_HANDLER_FRAME action for phase 2 unwinding.
1169 return _URC_HANDLER_FOUND;
1172 handler_type found_handler = check_action_record(context, &lsda,
1173 action.action_record, realEx, &selector, ex->adjustedPtr);
1174 // If there's no action record, we've only found a cleanup, so keep
1175 // searching for something real
1176 if (found_handler == handler_catch)
1178 // Cache the results for the phase 2 unwind, if we found a handler
1179 // and this is not a foreign exception.
1182 saveLandingPad(context, exceptionObject, ex, selector, action.landing_pad);
1183 ex->languageSpecificData = reinterpret_cast<const char*>(lsda_addr);
1184 ex->actionRecord = reinterpret_cast<const char*>(action.action_record);
1185 // ex->adjustedPtr is set when finding the action record.
1187 return _URC_HANDLER_FOUND;
1189 return continueUnwinding(exceptionObject, context);
1193 // If this is a foreign exception, we didn't have anywhere to cache the
1194 // lookup stuff, so we need to do it again. If this is either a forced
1195 // unwind, a foreign exception, or a cleanup, then we just install the
1196 // context for a cleanup.
1197 if (!(actions & _UA_HANDLER_FRAME))
1200 struct dwarf_eh_lsda lsda = parse_lsda(context, lsda_addr);
1201 dwarf_eh_find_callsite(context, &lsda, &action);
1202 if (0 == action.landing_pad) { return continueUnwinding(exceptionObject, context); }
1203 handler_type found_handler = check_action_record(context, &lsda,
1204 action.action_record, realEx, &selector, ex->adjustedPtr);
1205 // Ignore handlers this time.
1206 if (found_handler != handler_cleanup) { return continueUnwinding(exceptionObject, context); }
1207 pushCleanupException(exceptionObject, ex);
1209 else if (foreignException)
1211 struct dwarf_eh_lsda lsda = parse_lsda(context, lsda_addr);
1212 dwarf_eh_find_callsite(context, &lsda, &action);
1213 check_action_record(context, &lsda, action.action_record, realEx,
1214 &selector, ex->adjustedPtr);
1216 else if (ex->catchTemp == 0)
1218 // Uncaught exception in cleanup, calling terminate
1223 // Restore the saved info if we saved some last time.
1224 loadLandingPad(context, exceptionObject, ex, &selector, &action.landing_pad);
1226 ex->handlerSwitchValue = 0;
1230 _Unwind_SetIP(context, reinterpret_cast<unsigned long>(action.landing_pad));
1231 _Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
1232 reinterpret_cast<unsigned long>(exceptionObject));
1233 _Unwind_SetGR(context, __builtin_eh_return_data_regno(1), selector);
1235 return _URC_INSTALL_CONTEXT;
1239 * ABI function called when entering a catch statement. The argument is the
1240 * pointer passed out of the personality function. This is always the start of
1241 * the _Unwind_Exception object. The return value for this function is the
1242 * pointer to the caught exception, which is either the adjusted pointer (for
1243 * C++ exceptions) of the unadjusted pointer (for foreign exceptions).
1245 #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
1246 extern "C" void *__cxa_begin_catch(void *e) throw()
1248 extern "C" void *__cxa_begin_catch(void *e)
1251 // We can't call the fast version here, because if the first exception that
1252 // we see is a foreign exception then we won't have called it yet.
1253 __cxa_thread_info *ti = thread_info();
1254 __cxa_eh_globals *globals = &ti->globals;
1255 _Unwind_Exception *exceptionObject = static_cast<_Unwind_Exception*>(e);
1257 if (isCXXException(exceptionObject->exception_class))
1259 // Only exceptions thrown with a C++ exception throwing function will
1260 // increment this, so don't decrement it here.
1261 globals->uncaughtExceptions--;
1262 __cxa_exception *ex = exceptionFromPointer(exceptionObject);
1264 if (ex->handlerCount == 0)
1266 // Add this to the front of the list of exceptions being handled
1267 // and increment its handler count so that it won't be deleted
1269 ex->nextException = globals->caughtExceptions;
1270 globals->caughtExceptions = ex;
1273 if (ex->handlerCount < 0)
1275 // Rethrown exception is catched before end of catch block.
1276 // Clear the rethrow flag (make value positive) - we are allowed
1277 // to delete this exception at the end of the catch block, as long
1278 // as it isn't thrown again later.
1290 // __cxa_begin_catch() <- we are here
1293 ex->handlerCount = -ex->handlerCount + 1;
1299 ti->foreign_exception_state = __cxa_thread_info::none;
1301 return ex->adjustedPtr;
1305 // If this is a foreign exception, then we need to be able to
1306 // store it. We can't chain foreign exceptions, so we give up
1307 // if there are already some outstanding ones.
1308 if (globals->caughtExceptions != 0)
1312 globals->caughtExceptions = reinterpret_cast<__cxa_exception*>(exceptionObject);
1313 ti->foreign_exception_state = __cxa_thread_info::caught;
1315 // exceptionObject is the pointer to the _Unwind_Exception within the
1316 // __cxa_exception. The throw object is after this
1317 return (reinterpret_cast<char*>(exceptionObject) + sizeof(_Unwind_Exception));
1323 * ABI function called when exiting a catch block. This will free the current
1324 * exception if it is no longer referenced in other catch blocks.
1326 extern "C" void __cxa_end_catch()
1328 // We can call the fast version here because the slow version is called in
1329 // __cxa_throw(), which must have been called before we end a catch block
1330 __cxa_thread_info *ti = thread_info_fast();
1331 __cxa_eh_globals *globals = &ti->globals;
1332 __cxa_exception *ex = globals->caughtExceptions;
1334 assert(0 != ex && "Ending catch when no exception is on the stack!");
1336 if (ti->foreign_exception_state != __cxa_thread_info::none)
1338 if (ti->foreign_exception_state != __cxa_thread_info::rethrown)
1340 _Unwind_Exception *e = reinterpret_cast<_Unwind_Exception*>(ti->globals.caughtExceptions);
1341 if (e->exception_cleanup)
1342 e->exception_cleanup(_URC_FOREIGN_EXCEPTION_CAUGHT, e);
1344 globals->caughtExceptions = 0;
1345 ti->foreign_exception_state = __cxa_thread_info::none;
1349 bool deleteException = true;
1351 if (ex->handlerCount < 0)
1353 // exception was rethrown. Exception should not be deleted even if
1354 // handlerCount become zero.
1364 // __cxa_end_catch(); <- we are here
1370 deleteException = false;
1377 if (ex->handlerCount == 0)
1379 globals->caughtExceptions = ex->nextException;
1380 if (deleteException)
1382 releaseException(ex);
1388 * ABI function. Returns the type of the current exception.
1390 extern "C" std::type_info *__cxa_current_exception_type()
1392 __cxa_eh_globals *globals = __cxa_get_globals();
1393 __cxa_exception *ex = globals->caughtExceptions;
1394 return ex ? ex->exceptionType : 0;
1398 * Cleanup, ensures that `__cxa_end_catch` is called to balance an explicit
1399 * `__cxa_begin_catch` call.
1401 static void end_catch(char *)
1406 * ABI function, called when an exception specification is violated.
1408 * This function does not return.
1410 extern "C" void __cxa_call_unexpected(void*exception)
1412 _Unwind_Exception *exceptionObject = static_cast<_Unwind_Exception*>(exception);
1413 // Wrap the call to the unexpected handler in calls to `__cxa_begin_catch`
1414 // and `__cxa_end_catch` so that we correctly update exception counts if
1415 // the unexpected handler throws an exception.
1416 __cxa_begin_catch(exceptionObject);
1417 __attribute__((cleanup(end_catch)))
1419 if (exceptionObject->exception_class == exception_class)
1421 __cxa_exception *ex = exceptionFromPointer(exceptionObject);
1422 if (ex->unexpectedHandler)
1424 ex->unexpectedHandler();
1425 // Should not be reached.
1430 // Should not be reached.
1435 * ABI function, returns the adjusted pointer to the exception object.
1437 extern "C" void *__cxa_get_exception_ptr(void *exceptionObject)
1439 return exceptionFromPointer(exceptionObject)->adjustedPtr;
1443 * As an extension, we provide the ability for the unexpected and terminate
1444 * handlers to be thread-local. We default to the standards-compliant
1445 * behaviour where they are global.
1447 static bool thread_local_handlers = false;
1453 * Sets whether unexpected and terminate handlers should be thread-local.
1455 void set_use_thread_local_handlers(bool flag) throw()
1457 thread_local_handlers = flag;
1460 * Sets a thread-local unexpected handler.
1462 unexpected_handler set_unexpected(unexpected_handler f) throw()
1464 static __cxa_thread_info *info = thread_info();
1465 unexpected_handler old = info->unexpectedHandler;
1466 info->unexpectedHandler = f;
1470 * Sets a thread-local terminate handler.
1472 terminate_handler set_terminate(terminate_handler f) throw()
1474 static __cxa_thread_info *info = thread_info();
1475 terminate_handler old = info->terminateHandler;
1476 info->terminateHandler = f;
1484 * Sets the function that will be called when an exception specification is
1487 unexpected_handler set_unexpected(unexpected_handler f) throw()
1489 if (thread_local_handlers) { return pathscale::set_unexpected(f); }
1491 return unexpectedHandler.exchange(f);
1494 * Sets the function that is called to terminate the program.
1496 terminate_handler set_terminate(terminate_handler f) throw()
1498 if (thread_local_handlers) { return pathscale::set_terminate(f); }
1500 return terminateHandler.exchange(f);
1503 * Terminates the program, calling a custom terminate implementation if
1508 static __cxa_thread_info *info = thread_info();
1509 if (0 != info && 0 != info->terminateHandler)
1511 info->terminateHandler();
1512 // Should not be reached - a terminate handler is not expected to
1516 terminateHandler.load()();
1519 * Called when an unexpected exception is encountered (i.e. an exception
1520 * violates an exception specification). This calls abort() unless a
1521 * custom handler has been set..
1525 static __cxa_thread_info *info = thread_info();
1526 if (0 != info && 0 != info->unexpectedHandler)
1528 info->unexpectedHandler();
1529 // Should not be reached - a terminate handler is not expected to
1533 unexpectedHandler.load()();
1536 * Returns whether there are any exceptions currently being thrown that
1537 * have not been caught. This can occur inside a nested catch statement.
1539 bool uncaught_exception() throw()
1541 __cxa_thread_info *info = thread_info();
1542 return info->globals.uncaughtExceptions != 0;
1545 * Returns the number of exceptions currently being thrown that have not
1546 * been caught. This can occur inside a nested catch statement.
1548 int uncaught_exceptions() throw()
1550 __cxa_thread_info *info = thread_info();
1551 return info->globals.uncaughtExceptions;
1554 * Returns the current unexpected handler.
1556 unexpected_handler get_unexpected() throw()
1558 __cxa_thread_info *info = thread_info();
1559 if (info->unexpectedHandler)
1561 return info->unexpectedHandler;
1563 return unexpectedHandler.load();
1566 * Returns the current terminate handler.
1568 terminate_handler get_terminate() throw()
1570 __cxa_thread_info *info = thread_info();
1571 if (info->terminateHandler)
1573 return info->terminateHandler;
1575 return terminateHandler.load();
1578 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
1579 extern "C" _Unwind_Exception *__cxa_get_cleanup(void)
1581 __cxa_thread_info *info = thread_info_fast();
1582 _Unwind_Exception *exceptionObject = info->currentCleanup;
1583 if (isCXXException(exceptionObject->exception_class))
1585 __cxa_exception *ex = exceptionFromPointer(exceptionObject);
1587 if (ex->cleanupCount == 0)
1589 info->currentCleanup = ex->nextCleanup;
1590 ex->nextCleanup = 0;
1595 info->currentCleanup = 0;
1597 return exceptionObject;
1601 ".pushsection .text.__cxa_end_cleanup \n"
1602 ".global __cxa_end_cleanup \n"
1603 ".type __cxa_end_cleanup, \"function\" \n"
1604 "__cxa_end_cleanup: \n"
1605 " push {r1, r2, r3, r4} \n"
1607 " bl __cxa_get_cleanup \n"
1609 " pop {r1, r2, r3, r4} \n"
1610 " b _Unwind_Resume \n"