xref: /freebsd/contrib/libcxxrt/exception.cc (revision b740c88bfb6453416926271c089262e7164dace3)
1 /*
2  * Copyright 2010-2011 PathScale, Inc. All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions are met:
6  *
7  * 1. Redistributions of source code must retain the above copyright notice,
8  *    this list of conditions and the following disclaimer.
9  *
10  * 2. Redistributions in binary form must reproduce the above copyright notice,
11  *    this list of conditions and the following disclaimer in the documentation
12  *    and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
15  * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
16  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
17  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
18  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
19  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
20  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
21  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
22  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
23  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
24  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include <stdlib.h>
28 #include <dlfcn.h>
29 #include <stdio.h>
30 #include <string.h>
31 #include <stdint.h>
32 #include <pthread.h>
33 #include "typeinfo.h"
34 #include "dwarf_eh.h"
35 #include "atomic.h"
36 #include "cxxabi.h"
37 
38 #pragma weak pthread_key_create
39 #pragma weak pthread_setspecific
40 #pragma weak pthread_getspecific
41 #pragma weak pthread_once
42 #ifdef LIBCXXRT_WEAK_LOCKS
43 #pragma weak pthread_mutex_lock
44 #define pthread_mutex_lock(mtx) do {\
45 	if (pthread_mutex_lock) pthread_mutex_lock(mtx);\
46 	} while(0)
47 #pragma weak pthread_mutex_unlock
48 #define pthread_mutex_unlock(mtx) do {\
49 	if (pthread_mutex_unlock) pthread_mutex_unlock(mtx);\
50 	} while(0)
51 #pragma weak pthread_cond_signal
52 #define pthread_cond_signal(cv) do {\
53 	if (pthread_cond_signal) pthread_cond_signal(cv);\
54 	} while(0)
55 #pragma weak pthread_cond_wait
56 #define pthread_cond_wait(cv, mtx) do {\
57 	if (pthread_cond_wait) pthread_cond_wait(cv, mtx);\
58 	} while(0)
59 #endif
60 
61 using namespace ABI_NAMESPACE;
62 
63 /**
64  * Saves the result of the landing pad that we have found.  For ARM, this is
65  * stored in the generic unwind structure, while on other platforms it is
66  * stored in the C++ exception.
67  */
68 static void saveLandingPad(struct _Unwind_Context *context,
69                            struct _Unwind_Exception *ucb,
70                            struct __cxa_exception *ex,
71                            int selector,
72                            dw_eh_ptr_t landingPad)
73 {
74 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
75 	// On ARM, we store the saved exception in the generic part of the structure
76 	ucb->barrier_cache.sp = _Unwind_GetGR(context, 13);
77 	ucb->barrier_cache.bitpattern[1] = static_cast<uint32_t>(selector);
78 	ucb->barrier_cache.bitpattern[3] = reinterpret_cast<uint32_t>(landingPad);
79 #endif
80 	// Cache the results for the phase 2 unwind, if we found a handler
81 	// and this is not a foreign exception.
82 	if (ex)
83 	{
84 		ex->handlerSwitchValue = selector;
85 		ex->catchTemp = landingPad;
86 	}
87 }
88 
89 /**
90  * Loads the saved landing pad.  Returns 1 on success, 0 on failure.
91  */
92 static int loadLandingPad(struct _Unwind_Context *context,
93                           struct _Unwind_Exception *ucb,
94                           struct __cxa_exception *ex,
95                           unsigned long *selector,
96                           dw_eh_ptr_t *landingPad)
97 {
98 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
99 	*selector = ucb->barrier_cache.bitpattern[1];
100 	*landingPad = reinterpret_cast<dw_eh_ptr_t>(ucb->barrier_cache.bitpattern[3]);
101 	return 1;
102 #else
103 	if (ex)
104 	{
105 		*selector = ex->handlerSwitchValue;
106 		*landingPad = reinterpret_cast<dw_eh_ptr_t>(ex->catchTemp);
107 		return 0;
108 	}
109 	return 0;
110 #endif
111 }
112 
113 static inline _Unwind_Reason_Code continueUnwinding(struct _Unwind_Exception *ex,
114                                                     struct _Unwind_Context *context)
115 {
116 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
117 	if (__gnu_unwind_frame(ex, context) != _URC_OK) { return _URC_FAILURE; }
118 #endif
119 	return _URC_CONTINUE_UNWIND;
120 }
121 
122 
123 extern "C" void __cxa_free_exception(void *thrown_exception);
124 extern "C" void __cxa_free_dependent_exception(void *thrown_exception);
125 extern "C" void* __dynamic_cast(const void *sub,
126                                 const __class_type_info *src,
127                                 const __class_type_info *dst,
128                                 ptrdiff_t src2dst_offset);
129 
130 /**
131  * The type of a handler that has been found.
132  */
133 typedef enum
134 {
135 	/** No handler. */
136 	handler_none,
137 	/**
138 	 * A cleanup - the exception will propagate through this frame, but code
139 	 * must be run when this happens.
140 	 */
141 	handler_cleanup,
142 	/**
143 	 * A catch statement.  The exception will not propagate past this frame
144 	 * (without an explicit rethrow).
145 	 */
146 	handler_catch
147 } handler_type;
148 
149 /**
150  * Per-thread info required by the runtime.  We store a single structure
151  * pointer in thread-local storage, because this tends to be a scarce resource
152  * and it's impolite to steal all of it and not leave any for the rest of the
153  * program.
154  *
155  * Instances of this structure are allocated lazily - at most one per thread -
156  * and are destroyed on thread termination.
157  */
158 struct __cxa_thread_info
159 {
160 	/** The termination handler for this thread. */
161 	terminate_handler terminateHandler;
162 	/** The unexpected exception handler for this thread. */
163 	unexpected_handler unexpectedHandler;
164 	/**
165 	 * The number of emergency buffers held by this thread.  This is 0 in
166 	 * normal operation - the emergency buffers are only used when malloc()
167 	 * fails to return memory for allocating an exception.  Threads are not
168 	 * permitted to hold more than 4 emergency buffers (as per recommendation
169 	 * in ABI spec [3.3.1]).
170 	 */
171 	int emergencyBuffersHeld;
172 	/**
173 	 * The exception currently running in a cleanup.
174 	 */
175 	_Unwind_Exception *currentCleanup;
176 	/**
177 	 * Our state with respect to foreign exceptions.  Usually none, set to
178 	 * caught if we have just caught an exception and rethrown if we are
179 	 * rethrowing it.
180 	 */
181 	enum
182 	{
183 		none,
184 		caught,
185 		rethrown
186 	} foreign_exception_state;
187 	/**
188 	 * The public part of this structure, accessible from outside of this
189 	 * module.
190 	 */
191 	__cxa_eh_globals globals;
192 };
193 /**
194  * Dependent exception.  This
195  */
196 struct __cxa_dependent_exception
197 {
198 #if __LP64__
199 	void *primaryException;
200 #endif
201 	std::type_info *exceptionType;
202 	void (*exceptionDestructor) (void *);
203 	unexpected_handler unexpectedHandler;
204 	terminate_handler terminateHandler;
205 	__cxa_exception *nextException;
206 	int handlerCount;
207 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
208 	_Unwind_Exception *nextCleanup;
209 	int cleanupCount;
210 #endif
211 	int handlerSwitchValue;
212 	const char *actionRecord;
213 	const char *languageSpecificData;
214 	void *catchTemp;
215 	void *adjustedPtr;
216 #if !__LP64__
217 	void *primaryException;
218 #endif
219 	_Unwind_Exception unwindHeader;
220 };
221 
222 
223 namespace std
224 {
225 	void unexpected();
226 	class exception
227 	{
228 		public:
229 			virtual ~exception() throw();
230 			virtual const char* what() const throw();
231 	};
232 
233 }
234 
235 /**
236  * Class of exceptions to distinguish between this and other exception types.
237  *
238  * The first four characters are the vendor ID.  Currently, we use GNUC,
239  * because we aim for ABI-compatibility with the GNU implementation, and
240  * various checks may test for equality of the class, which is incorrect.
241  */
242 static const uint64_t exception_class =
243 	EXCEPTION_CLASS('G', 'N', 'U', 'C', 'C', '+', '+', '\0');
244 /**
245  * Class used for dependent exceptions.
246  */
247 static const uint64_t dependent_exception_class =
248 	EXCEPTION_CLASS('G', 'N', 'U', 'C', 'C', '+', '+', '\x01');
249 /**
250  * The low four bytes of the exception class, indicating that we conform to the
251  * Itanium C++ ABI.  This is currently unused, but should be used in the future
252  * if we change our exception class, to allow this library and libsupc++ to be
253  * linked to the same executable and both to interoperate.
254  */
255 static const uint32_t abi_exception_class =
256 	GENERIC_EXCEPTION_CLASS('C', '+', '+', '\0');
257 
258 static bool isCXXException(uint64_t cls)
259 {
260 	return (cls == exception_class) || (cls == dependent_exception_class);
261 }
262 
263 static bool isDependentException(uint64_t cls)
264 {
265 	return cls == dependent_exception_class;
266 }
267 
268 static __cxa_exception *exceptionFromPointer(void *ex)
269 {
270 	return reinterpret_cast<__cxa_exception*>(static_cast<char*>(ex) -
271 			offsetof(struct __cxa_exception, unwindHeader));
272 }
273 static __cxa_exception *realExceptionFromException(__cxa_exception *ex)
274 {
275 	if (!isDependentException(ex->unwindHeader.exception_class)) { return ex; }
276 	return reinterpret_cast<__cxa_exception*>((reinterpret_cast<__cxa_dependent_exception*>(ex))->primaryException)-1;
277 }
278 
279 
280 namespace std
281 {
282 	// Forward declaration of standard library terminate() function used to
283 	// abort execution.
284 	void terminate(void);
285 }
286 
287 using namespace ABI_NAMESPACE;
288 
289 
290 
291 /** The global termination handler. */
292 static terminate_handler terminateHandler = abort;
293 /** The global unexpected exception handler. */
294 static unexpected_handler unexpectedHandler = std::terminate;
295 
296 /** Key used for thread-local data. */
297 static pthread_key_t eh_key;
298 
299 
300 /**
301  * Cleanup function, allowing foreign exception handlers to correctly destroy
302  * this exception if they catch it.
303  */
304 static void exception_cleanup(_Unwind_Reason_Code reason,
305                               struct _Unwind_Exception *ex)
306 {
307 	__cxa_free_exception(static_cast<void*>(ex));
308 }
309 static void dependent_exception_cleanup(_Unwind_Reason_Code reason,
310                               struct _Unwind_Exception *ex)
311 {
312 
313 	__cxa_free_dependent_exception(static_cast<void*>(ex));
314 }
315 
316 /**
317  * Recursively walk a list of exceptions and delete them all in post-order.
318  */
319 static void free_exception_list(__cxa_exception *ex)
320 {
321 	if (0 != ex->nextException)
322 	{
323 		free_exception_list(ex->nextException);
324 	}
325 	// __cxa_free_exception() expects to be passed the thrown object, which
326 	// immediately follows the exception, not the exception itself
327 	__cxa_free_exception(ex+1);
328 }
329 
330 /**
331  * Cleanup function called when a thread exists to make certain that all of the
332  * per-thread data is deleted.
333  */
334 static void thread_cleanup(void* thread_info)
335 {
336 	__cxa_thread_info *info = static_cast<__cxa_thread_info*>(thread_info);
337 	if (info->globals.caughtExceptions)
338 	{
339 		// If this is a foreign exception, ask it to clean itself up.
340 		if (info->foreign_exception_state != __cxa_thread_info::none)
341 		{
342 			_Unwind_Exception *e = reinterpret_cast<_Unwind_Exception*>(info->globals.caughtExceptions);
343 			e->exception_cleanup(_URC_FOREIGN_EXCEPTION_CAUGHT, e);
344 		}
345 		else
346 		{
347 			free_exception_list(info->globals.caughtExceptions);
348 		}
349 	}
350 	free(thread_info);
351 }
352 
353 
354 /**
355  * Once control used to protect the key creation.
356  */
357 static pthread_once_t once_control = PTHREAD_ONCE_INIT;
358 
359 /**
360  * We may not be linked against a full pthread implementation.  If we're not,
361  * then we need to fake the thread-local storage by storing 'thread-local'
362  * things in a global.
363  */
364 static bool fakeTLS;
365 /**
366  * Thread-local storage for a single-threaded program.
367  */
368 static __cxa_thread_info singleThreadInfo;
369 /**
370  * Initialise eh_key.
371  */
372 static void init_key(void)
373 {
374 	if ((0 == pthread_key_create) ||
375 	    (0 == pthread_setspecific) ||
376 	    (0 == pthread_getspecific))
377 	{
378 		fakeTLS = true;
379 		return;
380 	}
381 	pthread_key_create(&eh_key, thread_cleanup);
382 	pthread_setspecific(eh_key, reinterpret_cast<void *>(0x42));
383 	fakeTLS = (pthread_getspecific(eh_key) != reinterpret_cast<void *>(0x42));
384 	pthread_setspecific(eh_key, 0);
385 }
386 
387 /**
388  * Returns the thread info structure, creating it if it is not already created.
389  */
390 static __cxa_thread_info *thread_info()
391 {
392 	if ((0 == pthread_once) || pthread_once(&once_control, init_key))
393 	{
394 		fakeTLS = true;
395 	}
396 	if (fakeTLS) { return &singleThreadInfo; }
397 	__cxa_thread_info *info = static_cast<__cxa_thread_info*>(pthread_getspecific(eh_key));
398 	if (0 == info)
399 	{
400 		info = static_cast<__cxa_thread_info*>(calloc(1, sizeof(__cxa_thread_info)));
401 		pthread_setspecific(eh_key, info);
402 	}
403 	return info;
404 }
405 /**
406  * Fast version of thread_info().  May fail if thread_info() is not called on
407  * this thread at least once already.
408  */
409 static __cxa_thread_info *thread_info_fast()
410 {
411 	if (fakeTLS) { return &singleThreadInfo; }
412 	return static_cast<__cxa_thread_info*>(pthread_getspecific(eh_key));
413 }
414 /**
415  * ABI function returning the __cxa_eh_globals structure.
416  */
417 extern "C" __cxa_eh_globals *ABI_NAMESPACE::__cxa_get_globals(void)
418 {
419 	return &(thread_info()->globals);
420 }
421 /**
422  * Version of __cxa_get_globals() assuming that __cxa_get_globals() has already
423  * been called at least once by this thread.
424  */
425 extern "C" __cxa_eh_globals *ABI_NAMESPACE::__cxa_get_globals_fast(void)
426 {
427 	return &(thread_info_fast()->globals);
428 }
429 
430 /**
431  * An emergency allocation reserved for when malloc fails.  This is treated as
432  * 16 buffers of 1KB each.
433  */
434 static char emergency_buffer[16384];
435 /**
436  * Flag indicating whether each buffer is allocated.
437  */
438 static bool buffer_allocated[16];
439 /**
440  * Lock used to protect emergency allocation.
441  */
442 static pthread_mutex_t emergency_malloc_lock = PTHREAD_MUTEX_INITIALIZER;
443 /**
444  * Condition variable used to wait when two threads are both trying to use the
445  * emergency malloc() buffer at once.
446  */
447 static pthread_cond_t emergency_malloc_wait = PTHREAD_COND_INITIALIZER;
448 
449 /**
450  * Allocates size bytes from the emergency allocation mechanism, if possible.
451  * This function will fail if size is over 1KB or if this thread already has 4
452  * emergency buffers.  If all emergency buffers are allocated, it will sleep
453  * until one becomes available.
454  */
455 static char *emergency_malloc(size_t size)
456 {
457 	if (size > 1024) { return 0; }
458 
459 	__cxa_thread_info *info = thread_info();
460 	// Only 4 emergency buffers allowed per thread!
461 	if (info->emergencyBuffersHeld > 3) { return 0; }
462 
463 	pthread_mutex_lock(&emergency_malloc_lock);
464 	int buffer = -1;
465 	while (buffer < 0)
466 	{
467 		// While we were sleeping on the lock, another thread might have free'd
468 		// enough memory for us to use, so try the allocation again - no point
469 		// using the emergency buffer if there is some real memory that we can
470 		// use...
471 		void *m = calloc(1, size);
472 		if (0 != m)
473 		{
474 			pthread_mutex_unlock(&emergency_malloc_lock);
475 			return static_cast<char*>(m);
476 		}
477 		for (int i=0 ; i<16 ; i++)
478 		{
479 			if (!buffer_allocated[i])
480 			{
481 				buffer = i;
482 				buffer_allocated[i] = true;
483 				break;
484 			}
485 		}
486 		// If there still isn't a buffer available, then sleep on the condition
487 		// variable.  This will be signalled when another thread releases one
488 		// of the emergency buffers.
489 		if (buffer < 0)
490 		{
491 			pthread_cond_wait(&emergency_malloc_wait, &emergency_malloc_lock);
492 		}
493 	}
494 	pthread_mutex_unlock(&emergency_malloc_lock);
495 	info->emergencyBuffersHeld++;
496 	return emergency_buffer + (1024 * buffer);
497 }
498 
499 /**
500  * Frees a buffer returned by emergency_malloc().
501  *
502  * Note: Neither this nor emergency_malloc() is particularly efficient.  This
503  * should not matter, because neither will be called in normal operation - they
504  * are only used when the program runs out of memory, which should not happen
505  * often.
506  */
507 static void emergency_malloc_free(char *ptr)
508 {
509 	int buffer = -1;
510 	// Find the buffer corresponding to this pointer.
511 	for (int i=0 ; i<16 ; i++)
512 	{
513 		if (ptr == static_cast<void*>(emergency_buffer + (1024 * i)))
514 		{
515 			buffer = i;
516 			break;
517 		}
518 	}
519 	assert(buffer > 0 &&
520 	       "Trying to free something that is not an emergency buffer!");
521 	// emergency_malloc() is expected to return 0-initialized data.  We don't
522 	// zero the buffer when allocating it, because the static buffers will
523 	// begin life containing 0 values.
524 	memset(ptr, 0, 1024);
525 	// Signal the condition variable to wake up any threads that are blocking
526 	// waiting for some space in the emergency buffer
527 	pthread_mutex_lock(&emergency_malloc_lock);
528 	// In theory, we don't need to do this with the lock held.  In practice,
529 	// our array of bools will probably be updated using 32-bit or 64-bit
530 	// memory operations, so this update may clobber adjacent values.
531 	buffer_allocated[buffer] = false;
532 	pthread_cond_signal(&emergency_malloc_wait);
533 	pthread_mutex_unlock(&emergency_malloc_lock);
534 }
535 
536 static char *alloc_or_die(size_t size)
537 {
538 	char *buffer = static_cast<char*>(calloc(1, size));
539 
540 	// If calloc() doesn't want to give us any memory, try using an emergency
541 	// buffer.
542 	if (0 == buffer)
543 	{
544 		buffer = emergency_malloc(size);
545 		// This is only reached if the allocation is greater than 1KB, and
546 		// anyone throwing objects that big really should know better.
547 		if (0 == buffer)
548 		{
549 			fprintf(stderr, "Out of memory attempting to allocate exception\n");
550 			std::terminate();
551 		}
552 	}
553 	return buffer;
554 }
555 static void free_exception(char *e)
556 {
557 	// If this allocation is within the address range of the emergency buffer,
558 	// don't call free() because it was not allocated with malloc()
559 	if ((e > emergency_buffer) &&
560 	    (e < (emergency_buffer + sizeof(emergency_buffer))))
561 	{
562 		emergency_malloc_free(e);
563 	}
564 	else
565 	{
566 		free(e);
567 	}
568 }
569 
570 /**
571  * Allocates an exception structure.  Returns a pointer to the space that can
572  * be used to store an object of thrown_size bytes.  This function will use an
573  * emergency buffer if malloc() fails, and may block if there are no such
574  * buffers available.
575  */
576 extern "C" void *__cxa_allocate_exception(size_t thrown_size)
577 {
578 	size_t size = thrown_size + sizeof(__cxa_exception);
579 	char *buffer = alloc_or_die(size);
580 	return buffer+sizeof(__cxa_exception);
581 }
582 
583 extern "C" void *__cxa_allocate_dependent_exception(void)
584 {
585 	size_t size = sizeof(__cxa_dependent_exception);
586 	char *buffer = alloc_or_die(size);
587 	return buffer+sizeof(__cxa_dependent_exception);
588 }
589 
590 /**
591  * __cxa_free_exception() is called when an exception was thrown in between
592  * calling __cxa_allocate_exception() and actually throwing the exception.
593  * This happens when the object's copy constructor throws an exception.
594  *
595  * In this implementation, it is also called by __cxa_end_catch() and during
596  * thread cleanup.
597  */
598 extern "C" void __cxa_free_exception(void *thrown_exception)
599 {
600 	__cxa_exception *ex = reinterpret_cast<__cxa_exception*>(thrown_exception) - 1;
601 	// Free the object that was thrown, calling its destructor
602 	if (0 != ex->exceptionDestructor)
603 	{
604 		try
605 		{
606 			ex->exceptionDestructor(thrown_exception);
607 		}
608 		catch(...)
609 		{
610 			// FIXME: Check that this is really what the spec says to do.
611 			std::terminate();
612 		}
613 	}
614 
615 	free_exception(reinterpret_cast<char*>(ex));
616 }
617 
618 static void releaseException(__cxa_exception *exception)
619 {
620 	if (isDependentException(exception->unwindHeader.exception_class))
621 	{
622 		__cxa_free_dependent_exception(exception+1);
623 		return;
624 	}
625 	if (__sync_sub_and_fetch(&exception->referenceCount, 1) == 0)
626 	{
627 		// __cxa_free_exception() expects to be passed the thrown object,
628 		// which immediately follows the exception, not the exception
629 		// itself
630 		__cxa_free_exception(exception+1);
631 	}
632 }
633 
634 void __cxa_free_dependent_exception(void *thrown_exception)
635 {
636 	__cxa_dependent_exception *ex = reinterpret_cast<__cxa_dependent_exception*>(thrown_exception) - 1;
637 	assert(isDependentException(ex->unwindHeader.exception_class));
638 	if (ex->primaryException)
639 	{
640 		releaseException(realExceptionFromException(reinterpret_cast<__cxa_exception*>(ex)));
641 	}
642 	free_exception(reinterpret_cast<char*>(ex));
643 }
644 
645 /**
646  * Callback function used with _Unwind_Backtrace().
647  *
648  * Prints a stack trace.  Used only for debugging help.
649  *
650  * Note: As of FreeBSD 8.1, dladd() still doesn't work properly, so this only
651  * correctly prints function names from public, relocatable, symbols.
652  */
653 static _Unwind_Reason_Code trace(struct _Unwind_Context *context, void *c)
654 {
655 	Dl_info myinfo;
656 	int mylookup =
657 		dladdr(reinterpret_cast<void *>(__cxa_current_exception_type), &myinfo);
658 	void *ip = reinterpret_cast<void*>(_Unwind_GetIP(context));
659 	Dl_info info;
660 	if (dladdr(ip, &info) != 0)
661 	{
662 		if (mylookup == 0 || strcmp(info.dli_fname, myinfo.dli_fname) != 0)
663 		{
664 			printf("%p:%s() in %s\n", ip, info.dli_sname, info.dli_fname);
665 		}
666 	}
667 	return _URC_CONTINUE_UNWIND;
668 }
669 
670 /**
671  * Report a failure that occurred when attempting to throw an exception.
672  *
673  * If the failure happened by falling off the end of the stack without finding
674  * a handler, prints a back trace before aborting.
675  */
676 #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
677 extern "C" void *__cxa_begin_catch(void *e) throw();
678 #else
679 extern "C" void *__cxa_begin_catch(void *e);
680 #endif
681 static void report_failure(_Unwind_Reason_Code err, __cxa_exception *thrown_exception)
682 {
683 	switch (err)
684 	{
685 		default: break;
686 		case _URC_FATAL_PHASE1_ERROR:
687 			fprintf(stderr, "Fatal error during phase 1 unwinding\n");
688 			break;
689 #if !defined(__arm__) || defined(__ARM_DWARF_EH__)
690 		case _URC_FATAL_PHASE2_ERROR:
691 			fprintf(stderr, "Fatal error during phase 2 unwinding\n");
692 			break;
693 #endif
694 		case _URC_END_OF_STACK:
695 			__cxa_begin_catch (&(thrown_exception->unwindHeader));
696  			std::terminate();
697 			fprintf(stderr, "Terminating due to uncaught exception %p",
698 					static_cast<void*>(thrown_exception));
699 			thrown_exception = realExceptionFromException(thrown_exception);
700 			static const __class_type_info *e_ti =
701 				static_cast<const __class_type_info*>(&typeid(std::exception));
702 			const __class_type_info *throw_ti =
703 				dynamic_cast<const __class_type_info*>(thrown_exception->exceptionType);
704 			if (throw_ti)
705 			{
706 				std::exception *e =
707 					static_cast<std::exception*>(e_ti->cast_to(static_cast<void*>(thrown_exception+1),
708 							throw_ti));
709 				if (e)
710 				{
711 					fprintf(stderr, " '%s'", e->what());
712 				}
713 			}
714 
715 			size_t bufferSize = 128;
716 			char *demangled = static_cast<char*>(malloc(bufferSize));
717 			const char *mangled = thrown_exception->exceptionType->name();
718 			int status;
719 			demangled = __cxa_demangle(mangled, demangled, &bufferSize, &status);
720 			fprintf(stderr, " of type %s\n",
721 				status == 0 ? demangled : mangled);
722 			if (status == 0) { free(demangled); }
723 			// Print a back trace if no handler is found.
724 			// TODO: Make this optional
725 #ifndef __arm__
726 			_Unwind_Backtrace(trace, 0);
727 #endif
728 
729 			// Just abort. No need to call std::terminate for the second time
730 			abort();
731 			break;
732 	}
733 	std::terminate();
734 }
735 
736 static void throw_exception(__cxa_exception *ex)
737 {
738 	__cxa_thread_info *info = thread_info();
739 	ex->unexpectedHandler = info->unexpectedHandler;
740 	if (0 == ex->unexpectedHandler)
741 	{
742 		ex->unexpectedHandler = unexpectedHandler;
743 	}
744 	ex->terminateHandler  = info->terminateHandler;
745 	if (0 == ex->terminateHandler)
746 	{
747 		ex->terminateHandler = terminateHandler;
748 	}
749 	info->globals.uncaughtExceptions++;
750 
751 	_Unwind_Reason_Code err = _Unwind_RaiseException(&ex->unwindHeader);
752 	// The _Unwind_RaiseException() function should not return, it should
753 	// unwind the stack past this function.  If it does return, then something
754 	// has gone wrong.
755 	report_failure(err, ex);
756 }
757 
758 
759 /**
760  * ABI function for throwing an exception.  Takes the object to be thrown (the
761  * pointer returned by __cxa_allocate_exception()), the type info for the
762  * pointee, and the destructor (if there is one) as arguments.
763  */
764 extern "C" void __cxa_throw(void *thrown_exception,
765                             std::type_info *tinfo,
766                             void(*dest)(void*))
767 {
768 	__cxa_exception *ex = reinterpret_cast<__cxa_exception*>(thrown_exception) - 1;
769 
770 	ex->referenceCount = 1;
771 	ex->exceptionType = tinfo;
772 
773 	ex->exceptionDestructor = dest;
774 
775 	ex->unwindHeader.exception_class = exception_class;
776 	ex->unwindHeader.exception_cleanup = exception_cleanup;
777 
778 	throw_exception(ex);
779 }
780 
781 extern "C" void __cxa_rethrow_primary_exception(void* thrown_exception)
782 {
783 	if (NULL == thrown_exception) { return; }
784 
785 	__cxa_exception *original = exceptionFromPointer(thrown_exception);
786 	__cxa_dependent_exception *ex = reinterpret_cast<__cxa_dependent_exception*>(__cxa_allocate_dependent_exception())-1;
787 
788 	ex->primaryException = thrown_exception;
789 	__cxa_increment_exception_refcount(thrown_exception);
790 
791 	ex->exceptionType = original->exceptionType;
792 	ex->unwindHeader.exception_class = dependent_exception_class;
793 	ex->unwindHeader.exception_cleanup = dependent_exception_cleanup;
794 
795 	throw_exception(reinterpret_cast<__cxa_exception*>(ex));
796 }
797 
798 extern "C" void *__cxa_current_primary_exception(void)
799 {
800 	__cxa_eh_globals* globals = __cxa_get_globals();
801 	__cxa_exception *ex = globals->caughtExceptions;
802 
803 	if (0 == ex) { return NULL; }
804 	ex = realExceptionFromException(ex);
805 	__sync_fetch_and_add(&ex->referenceCount, 1);
806 	return ex + 1;
807 }
808 
809 extern "C" void __cxa_increment_exception_refcount(void* thrown_exception)
810 {
811 	if (NULL == thrown_exception) { return; }
812 	__cxa_exception *ex = static_cast<__cxa_exception*>(thrown_exception) - 1;
813 	if (isDependentException(ex->unwindHeader.exception_class)) { return; }
814 	__sync_fetch_and_add(&ex->referenceCount, 1);
815 }
816 extern "C" void __cxa_decrement_exception_refcount(void* thrown_exception)
817 {
818 	if (NULL == thrown_exception) { return; }
819 	__cxa_exception *ex = static_cast<__cxa_exception*>(thrown_exception) - 1;
820 	releaseException(ex);
821 }
822 
823 /**
824  * ABI function.  Rethrows the current exception.  Does not remove the
825  * exception from the stack or decrement its handler count - the compiler is
826  * expected to set the landing pad for this function to the end of the catch
827  * block, and then call _Unwind_Resume() to continue unwinding once
828  * __cxa_end_catch() has been called and any cleanup code has been run.
829  */
830 extern "C" void __cxa_rethrow()
831 {
832 	__cxa_thread_info *ti = thread_info();
833 	__cxa_eh_globals *globals = &ti->globals;
834 	// Note: We don't remove this from the caught list here, because
835 	// __cxa_end_catch will be called when we unwind out of the try block.  We
836 	// could probably make this faster by providing an alternative rethrow
837 	// function and ensuring that all cleanup code is run before calling it, so
838 	// we can skip the top stack frame when unwinding.
839 	__cxa_exception *ex = globals->caughtExceptions;
840 
841 	if (0 == ex)
842 	{
843 		fprintf(stderr,
844 		        "Attempting to rethrow an exception that doesn't exist!\n");
845 		std::terminate();
846 	}
847 
848 	if (ti->foreign_exception_state != __cxa_thread_info::none)
849 	{
850 		ti->foreign_exception_state = __cxa_thread_info::rethrown;
851 		_Unwind_Exception *e = reinterpret_cast<_Unwind_Exception*>(ex);
852 		_Unwind_Reason_Code err = _Unwind_Resume_or_Rethrow(e);
853 		report_failure(err, ex);
854 		return;
855 	}
856 
857 	assert(ex->handlerCount > 0 && "Rethrowing uncaught exception!");
858 
859 	// ex->handlerCount will be decremented in __cxa_end_catch in enclosing
860 	// catch block
861 
862 	// Make handler count negative. This will tell __cxa_end_catch that
863 	// exception was rethrown and exception object should not be destroyed
864 	// when handler count become zero
865 	ex->handlerCount = -ex->handlerCount;
866 
867 	// Continue unwinding the stack with this exception.  This should unwind to
868 	// the place in the caller where __cxa_end_catch() is called.  The caller
869 	// will then run cleanup code and bounce the exception back with
870 	// _Unwind_Resume().
871 	_Unwind_Reason_Code err = _Unwind_Resume_or_Rethrow(&ex->unwindHeader);
872 	report_failure(err, ex);
873 }
874 
875 /**
876  * Returns the type_info object corresponding to the filter.
877  */
878 static std::type_info *get_type_info_entry(_Unwind_Context *context,
879                                            dwarf_eh_lsda *lsda,
880                                            int filter)
881 {
882 	// Get the address of the record in the table.
883 	dw_eh_ptr_t record = lsda->type_table -
884 		dwarf_size_of_fixed_size_field(lsda->type_table_encoding)*filter;
885 	//record -= 4;
886 	dw_eh_ptr_t start = record;
887 	// Read the value, but it's probably an indirect reference...
888 	int64_t offset = read_value(lsda->type_table_encoding, &record);
889 
890 	// (If the entry is 0, don't try to dereference it.  That would be bad.)
891 	if (offset == 0) { return 0; }
892 
893 	// ...so we need to resolve it
894 	return reinterpret_cast<std::type_info*>(resolve_indirect_value(context,
895 			lsda->type_table_encoding, offset, start));
896 }
897 
898 
899 
900 /**
901  * Checks the type signature found in a handler against the type of the thrown
902  * object.  If ex is 0 then it is assumed to be a foreign exception and only
903  * matches cleanups.
904  */
905 static bool check_type_signature(__cxa_exception *ex,
906                                  const std::type_info *type,
907                                  void *&adjustedPtr)
908 {
909 	void *exception_ptr = static_cast<void*>(ex+1);
910 	const std::type_info *ex_type = ex ? ex->exceptionType : 0;
911 
912 	bool is_ptr = ex ? ex_type->__is_pointer_p() : false;
913 	if (is_ptr)
914 	{
915 		exception_ptr = *static_cast<void**>(exception_ptr);
916 	}
917 	// Always match a catchall, even with a foreign exception
918 	//
919 	// Note: A 0 here is a catchall, not a cleanup, so we return true to
920 	// indicate that we found a catch.
921 	if (0 == type)
922 	{
923 		if (ex)
924 		{
925 			adjustedPtr = exception_ptr;
926 		}
927 		return true;
928 	}
929 
930 	if (0 == ex) { return false; }
931 
932 	// If the types are the same, no casting is needed.
933 	if (*type == *ex_type)
934 	{
935 		adjustedPtr = exception_ptr;
936 		return true;
937 	}
938 
939 
940 	if (type->__do_catch(ex_type, &exception_ptr, 1))
941 	{
942 		adjustedPtr = exception_ptr;
943 		return true;
944 	}
945 
946 	return false;
947 }
948 /**
949  * Checks whether the exception matches the type specifiers in this action
950  * record.  If the exception only matches cleanups, then this returns false.
951  * If it matches a catch (including a catchall) then it returns true.
952  *
953  * The selector argument is used to return the selector that is passed in the
954  * second exception register when installing the context.
955  */
956 static handler_type check_action_record(_Unwind_Context *context,
957                                         dwarf_eh_lsda *lsda,
958                                         dw_eh_ptr_t action_record,
959                                         __cxa_exception *ex,
960                                         unsigned long *selector,
961                                         void *&adjustedPtr)
962 {
963 	if (!action_record) { return handler_cleanup; }
964 	handler_type found = handler_none;
965 	while (action_record)
966 	{
967 		int filter = read_sleb128(&action_record);
968 		dw_eh_ptr_t action_record_offset_base = action_record;
969 		int displacement = read_sleb128(&action_record);
970 		action_record = displacement ?
971 			action_record_offset_base + displacement : 0;
972 		// We only check handler types for C++ exceptions - foreign exceptions
973 		// are only allowed for cleanups and catchalls.
974 		if (filter > 0)
975 		{
976 			std::type_info *handler_type = get_type_info_entry(context, lsda, filter);
977 			if (check_type_signature(ex, handler_type, adjustedPtr))
978 			{
979 				*selector = filter;
980 				return handler_catch;
981 			}
982 		}
983 		else if (filter < 0 && 0 != ex)
984 		{
985 			bool matched = false;
986 			*selector = filter;
987 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
988 			filter++;
989 			std::type_info *handler_type = get_type_info_entry(context, lsda, filter--);
990 			while (handler_type)
991 			{
992 				if (check_type_signature(ex, handler_type, adjustedPtr))
993 				{
994 					matched = true;
995 					break;
996 				}
997 				handler_type = get_type_info_entry(context, lsda, filter--);
998 			}
999 #else
1000 			unsigned char *type_index = reinterpret_cast<unsigned char*>(lsda->type_table) - filter - 1;
1001 			while (*type_index)
1002 			{
1003 				std::type_info *handler_type = get_type_info_entry(context, lsda, *(type_index++));
1004 				// If the exception spec matches a permitted throw type for
1005 				// this function, don't report a handler - we are allowed to
1006 				// propagate this exception out.
1007 				if (check_type_signature(ex, handler_type, adjustedPtr))
1008 				{
1009 					matched = true;
1010 					break;
1011 				}
1012 			}
1013 #endif
1014 			if (matched) { continue; }
1015 			// If we don't find an allowed exception spec, we need to install
1016 			// the context for this action.  The landing pad will then call the
1017 			// unexpected exception function.  Treat this as a catch
1018 			return handler_catch;
1019 		}
1020 		else if (filter == 0)
1021 		{
1022 			*selector = filter;
1023 			found = handler_cleanup;
1024 		}
1025 	}
1026 	return found;
1027 }
1028 
1029 static void pushCleanupException(_Unwind_Exception *exceptionObject,
1030                                  __cxa_exception *ex)
1031 {
1032 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
1033 	__cxa_thread_info *info = thread_info_fast();
1034 	if (ex)
1035 	{
1036 		ex->cleanupCount++;
1037 		if (ex->cleanupCount > 1)
1038 		{
1039 			assert(exceptionObject == info->currentCleanup);
1040 			return;
1041 		}
1042 		ex->nextCleanup = info->currentCleanup;
1043 	}
1044 	info->currentCleanup = exceptionObject;
1045 #endif
1046 }
1047 
1048 /**
1049  * The exception personality function.  This is referenced in the unwinding
1050  * DWARF metadata and is called by the unwind library for each C++ stack frame
1051  * containing catch or cleanup code.
1052  */
1053 extern "C"
1054 BEGIN_PERSONALITY_FUNCTION(__gxx_personality_v0)
1055 	// This personality function is for version 1 of the ABI.  If you use it
1056 	// with a future version of the ABI, it won't know what to do, so it
1057 	// reports a fatal error and give up before it breaks anything.
1058 	if (1 != version)
1059 	{
1060 		return _URC_FATAL_PHASE1_ERROR;
1061 	}
1062 	__cxa_exception *ex = 0;
1063 	__cxa_exception *realEx = 0;
1064 
1065 	// If this exception is throw by something else then we can't make any
1066 	// assumptions about its layout beyond the fields declared in
1067 	// _Unwind_Exception.
1068 	bool foreignException = !isCXXException(exceptionClass);
1069 
1070 	// If this isn't a foreign exception, then we have a C++ exception structure
1071 	if (!foreignException)
1072 	{
1073 		ex = exceptionFromPointer(exceptionObject);
1074 		realEx = realExceptionFromException(ex);
1075 	}
1076 
1077 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
1078 	unsigned char *lsda_addr =
1079 		static_cast<unsigned char*>(_Unwind_GetLanguageSpecificData(context));
1080 #else
1081 	unsigned char *lsda_addr =
1082 		reinterpret_cast<unsigned char*>(static_cast<uintptr_t>(_Unwind_GetLanguageSpecificData(context)));
1083 #endif
1084 
1085 	// No LSDA implies no landing pads - try the next frame
1086 	if (0 == lsda_addr) { return continueUnwinding(exceptionObject, context); }
1087 
1088 	// These two variables define how the exception will be handled.
1089 	dwarf_eh_action action = {0};
1090 	unsigned long selector = 0;
1091 
1092 	// During the search phase, we do a complete lookup.  If we return
1093 	// _URC_HANDLER_FOUND, then the phase 2 unwind will call this function with
1094 	// a _UA_HANDLER_FRAME action, telling us to install the handler frame.  If
1095 	// we return _URC_CONTINUE_UNWIND, we may be called again later with a
1096 	// _UA_CLEANUP_PHASE action for this frame.
1097 	//
1098 	// The point of the two-stage unwind allows us to entirely avoid any stack
1099 	// unwinding if there is no handler.  If there are just cleanups found,
1100 	// then we can just panic call an abort function.
1101 	//
1102 	// Matching a handler is much more expensive than matching a cleanup,
1103 	// because we don't need to bother doing type comparisons (or looking at
1104 	// the type table at all) for a cleanup.  This means that there is no need
1105 	// to cache the result of finding a cleanup, because it's (quite) quick to
1106 	// look it up again from the action table.
1107 	if (actions & _UA_SEARCH_PHASE)
1108 	{
1109 		struct dwarf_eh_lsda lsda = parse_lsda(context, lsda_addr);
1110 
1111 		if (!dwarf_eh_find_callsite(context, &lsda, &action))
1112 		{
1113 			// EH range not found. This happens if exception is thrown and not
1114 			// caught inside a cleanup (destructor).  We should call
1115 			// terminate() in this case.  The catchTemp (landing pad) field of
1116 			// exception object will contain null when personality function is
1117 			// called with _UA_HANDLER_FRAME action for phase 2 unwinding.
1118 			return _URC_HANDLER_FOUND;
1119 		}
1120 
1121 		handler_type found_handler = check_action_record(context, &lsda,
1122 				action.action_record, realEx, &selector, ex->adjustedPtr);
1123 		// If there's no action record, we've only found a cleanup, so keep
1124 		// searching for something real
1125 		if (found_handler == handler_catch)
1126 		{
1127 			// Cache the results for the phase 2 unwind, if we found a handler
1128 			// and this is not a foreign exception.
1129 			if (ex)
1130 			{
1131 				saveLandingPad(context, exceptionObject, ex, selector, action.landing_pad);
1132 				ex->languageSpecificData = reinterpret_cast<const char*>(lsda_addr);
1133 				ex->actionRecord = reinterpret_cast<const char*>(action.action_record);
1134 				// ex->adjustedPtr is set when finding the action record.
1135 			}
1136 			return _URC_HANDLER_FOUND;
1137 		}
1138 		return continueUnwinding(exceptionObject, context);
1139 	}
1140 
1141 
1142 	// If this is a foreign exception, we didn't have anywhere to cache the
1143 	// lookup stuff, so we need to do it again.  If this is either a forced
1144 	// unwind, a foreign exception, or a cleanup, then we just install the
1145 	// context for a cleanup.
1146 	if (!(actions & _UA_HANDLER_FRAME))
1147 	{
1148 		// cleanup
1149 		struct dwarf_eh_lsda lsda = parse_lsda(context, lsda_addr);
1150 		dwarf_eh_find_callsite(context, &lsda, &action);
1151 		if (0 == action.landing_pad) { return continueUnwinding(exceptionObject, context); }
1152 		handler_type found_handler = check_action_record(context, &lsda,
1153 				action.action_record, realEx, &selector, ex->adjustedPtr);
1154 		// Ignore handlers this time.
1155 		if (found_handler != handler_cleanup) { return continueUnwinding(exceptionObject, context); }
1156 		pushCleanupException(exceptionObject, ex);
1157 	}
1158 	else if (foreignException)
1159 	{
1160 		struct dwarf_eh_lsda lsda = parse_lsda(context, lsda_addr);
1161 		dwarf_eh_find_callsite(context, &lsda, &action);
1162 		check_action_record(context, &lsda, action.action_record, realEx,
1163 				&selector, ex->adjustedPtr);
1164 	}
1165 	else if (ex->catchTemp == 0)
1166 	{
1167 		// Uncaught exception in cleanup, calling terminate
1168 		std::terminate();
1169 	}
1170 	else
1171 	{
1172 		// Restore the saved info if we saved some last time.
1173 		loadLandingPad(context, exceptionObject, ex, &selector, &action.landing_pad);
1174 		ex->catchTemp = 0;
1175 		ex->handlerSwitchValue = 0;
1176 	}
1177 
1178 
1179 	_Unwind_SetIP(context, reinterpret_cast<unsigned long>(action.landing_pad));
1180 	_Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
1181 	              reinterpret_cast<unsigned long>(exceptionObject));
1182 	_Unwind_SetGR(context, __builtin_eh_return_data_regno(1), selector);
1183 
1184 	return _URC_INSTALL_CONTEXT;
1185 }
1186 
1187 /**
1188  * ABI function called when entering a catch statement.  The argument is the
1189  * pointer passed out of the personality function.  This is always the start of
1190  * the _Unwind_Exception object.  The return value for this function is the
1191  * pointer to the caught exception, which is either the adjusted pointer (for
1192  * C++ exceptions) of the unadjusted pointer (for foreign exceptions).
1193  */
1194 #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)
1195 extern "C" void *__cxa_begin_catch(void *e) throw()
1196 #else
1197 extern "C" void *__cxa_begin_catch(void *e)
1198 #endif
1199 {
1200 	// We can't call the fast version here, because if the first exception that
1201 	// we see is a foreign exception then we won't have called it yet.
1202 	__cxa_thread_info *ti = thread_info();
1203 	__cxa_eh_globals *globals = &ti->globals;
1204 	globals->uncaughtExceptions--;
1205 	_Unwind_Exception *exceptionObject = static_cast<_Unwind_Exception*>(e);
1206 
1207 	if (isCXXException(exceptionObject->exception_class))
1208 	{
1209 		__cxa_exception *ex =  exceptionFromPointer(exceptionObject);
1210 
1211 		if (ex->handlerCount == 0)
1212 		{
1213 			// Add this to the front of the list of exceptions being handled
1214 			// and increment its handler count so that it won't be deleted
1215 			// prematurely.
1216 			ex->nextException = globals->caughtExceptions;
1217 			globals->caughtExceptions = ex;
1218 		}
1219 
1220 		if (ex->handlerCount < 0)
1221 		{
1222 			// Rethrown exception is catched before end of catch block.
1223 			// Clear the rethrow flag (make value positive) - we are allowed
1224 			// to delete this exception at the end of the catch block, as long
1225 			// as it isn't thrown again later.
1226 
1227 			// Code pattern:
1228 			//
1229 			// try {
1230 			//     throw x;
1231 			// }
1232 			// catch() {
1233 			//     try {
1234 			//         throw;
1235 			//     }
1236 			//     catch() {
1237 			//         __cxa_begin_catch() <- we are here
1238 			//     }
1239 			// }
1240 			ex->handlerCount = -ex->handlerCount + 1;
1241 		}
1242 		else
1243 		{
1244 			ex->handlerCount++;
1245 		}
1246 		ti->foreign_exception_state = __cxa_thread_info::none;
1247 
1248 		return ex->adjustedPtr;
1249 	}
1250 	else
1251 	{
1252 		// If this is a foreign exception, then we need to be able to
1253 		// store it.  We can't chain foreign exceptions, so we give up
1254 		// if there are already some outstanding ones.
1255 		if (globals->caughtExceptions != 0)
1256 		{
1257 			std::terminate();
1258 		}
1259 		globals->caughtExceptions = reinterpret_cast<__cxa_exception*>(exceptionObject);
1260 		ti->foreign_exception_state = __cxa_thread_info::caught;
1261 	}
1262 	// exceptionObject is the pointer to the _Unwind_Exception within the
1263 	// __cxa_exception.  The throw object is after this
1264 	return (reinterpret_cast<char*>(exceptionObject) + sizeof(_Unwind_Exception));
1265 }
1266 
1267 
1268 
1269 /**
1270  * ABI function called when exiting a catch block.  This will free the current
1271  * exception if it is no longer referenced in other catch blocks.
1272  */
1273 extern "C" void __cxa_end_catch()
1274 {
1275 	// We can call the fast version here because the slow version is called in
1276 	// __cxa_throw(), which must have been called before we end a catch block
1277 	__cxa_thread_info *ti = thread_info_fast();
1278 	__cxa_eh_globals *globals = &ti->globals;
1279 	__cxa_exception *ex = globals->caughtExceptions;
1280 
1281 	assert(0 != ex && "Ending catch when no exception is on the stack!");
1282 
1283 	if (ti->foreign_exception_state != __cxa_thread_info::none)
1284 	{
1285 		globals->caughtExceptions = 0;
1286 		if (ti->foreign_exception_state != __cxa_thread_info::rethrown)
1287 		{
1288 			_Unwind_Exception *e = reinterpret_cast<_Unwind_Exception*>(ti->globals.caughtExceptions);
1289 			e->exception_cleanup(_URC_FOREIGN_EXCEPTION_CAUGHT, e);
1290 		}
1291 		ti->foreign_exception_state = __cxa_thread_info::none;
1292 		return;
1293 	}
1294 
1295 	bool deleteException = true;
1296 
1297 	if (ex->handlerCount < 0)
1298 	{
1299 		// exception was rethrown. Exception should not be deleted even if
1300 		// handlerCount become zero.
1301 		// Code pattern:
1302 		// try {
1303 		//     throw x;
1304 		// }
1305 		// catch() {
1306 		//     {
1307 		//         throw;
1308 		//     }
1309 		//     cleanup {
1310 		//         __cxa_end_catch();   <- we are here
1311 		//     }
1312 		// }
1313 		//
1314 
1315 		ex->handlerCount++;
1316 		deleteException = false;
1317 	}
1318 	else
1319 	{
1320 		ex->handlerCount--;
1321 	}
1322 
1323 	if (ex->handlerCount == 0)
1324 	{
1325 		globals->caughtExceptions = ex->nextException;
1326 		if (deleteException)
1327 		{
1328 			releaseException(ex);
1329 		}
1330 	}
1331 }
1332 
1333 /**
1334  * ABI function.  Returns the type of the current exception.
1335  */
1336 extern "C" std::type_info *__cxa_current_exception_type()
1337 {
1338 	__cxa_eh_globals *globals = __cxa_get_globals();
1339 	__cxa_exception *ex = globals->caughtExceptions;
1340 	return ex ? ex->exceptionType : 0;
1341 }
1342 
1343 /**
1344  * ABI function, called when an exception specification is violated.
1345  *
1346  * This function does not return.
1347  */
1348 extern "C" void __cxa_call_unexpected(void*exception)
1349 {
1350 	_Unwind_Exception *exceptionObject = static_cast<_Unwind_Exception*>(exception);
1351 	if (exceptionObject->exception_class == exception_class)
1352 	{
1353 		__cxa_exception *ex =  exceptionFromPointer(exceptionObject);
1354 		if (ex->unexpectedHandler)
1355 		{
1356 			ex->unexpectedHandler();
1357 			// Should not be reached.
1358 			abort();
1359 		}
1360 	}
1361 	std::unexpected();
1362 	// Should not be reached.
1363 	abort();
1364 }
1365 
1366 /**
1367  * ABI function, returns the adjusted pointer to the exception object.
1368  */
1369 extern "C" void *__cxa_get_exception_ptr(void *exceptionObject)
1370 {
1371 	return exceptionFromPointer(exceptionObject)->adjustedPtr;
1372 }
1373 
1374 /**
1375  * As an extension, we provide the ability for the unexpected and terminate
1376  * handlers to be thread-local.  We default to the standards-compliant
1377  * behaviour where they are global.
1378  */
1379 static bool thread_local_handlers = false;
1380 
1381 
1382 namespace pathscale
1383 {
1384 	/**
1385 	 * Sets whether unexpected and terminate handlers should be thread-local.
1386 	 */
1387 	void set_use_thread_local_handlers(bool flag) throw()
1388 	{
1389 		thread_local_handlers = flag;
1390 	}
1391 	/**
1392 	 * Sets a thread-local unexpected handler.
1393 	 */
1394 	unexpected_handler set_unexpected(unexpected_handler f) throw()
1395 	{
1396 		static __cxa_thread_info *info = thread_info();
1397 		unexpected_handler old = info->unexpectedHandler;
1398 		info->unexpectedHandler = f;
1399 		return old;
1400 	}
1401 	/**
1402 	 * Sets a thread-local terminate handler.
1403 	 */
1404 	terminate_handler set_terminate(terminate_handler f) throw()
1405 	{
1406 		static __cxa_thread_info *info = thread_info();
1407 		terminate_handler old = info->terminateHandler;
1408 		info->terminateHandler = f;
1409 		return old;
1410 	}
1411 }
1412 
1413 namespace std
1414 {
1415 	/**
1416 	 * Sets the function that will be called when an exception specification is
1417 	 * violated.
1418 	 */
1419 	unexpected_handler set_unexpected(unexpected_handler f) throw()
1420 	{
1421 		if (thread_local_handlers) { return pathscale::set_unexpected(f); }
1422 
1423 		return ATOMIC_SWAP(&unexpectedHandler, f);
1424 	}
1425 	/**
1426 	 * Sets the function that is called to terminate the program.
1427 	 */
1428 	terminate_handler set_terminate(terminate_handler f) throw()
1429 	{
1430 		if (thread_local_handlers) { return pathscale::set_terminate(f); }
1431 
1432 		return ATOMIC_SWAP(&terminateHandler, f);
1433 	}
1434 	/**
1435 	 * Terminates the program, calling a custom terminate implementation if
1436 	 * required.
1437 	 */
1438 	void terminate()
1439 	{
1440 		static __cxa_thread_info *info = thread_info();
1441 		if (0 != info && 0 != info->terminateHandler)
1442 		{
1443 			info->terminateHandler();
1444 			// Should not be reached - a terminate handler is not expected to
1445 			// return.
1446 			abort();
1447 		}
1448 		terminateHandler();
1449 	}
1450 	/**
1451 	 * Called when an unexpected exception is encountered (i.e. an exception
1452 	 * violates an exception specification).  This calls abort() unless a
1453 	 * custom handler has been set..
1454 	 */
1455 	void unexpected()
1456 	{
1457 		static __cxa_thread_info *info = thread_info();
1458 		if (0 != info && 0 != info->unexpectedHandler)
1459 		{
1460 			info->unexpectedHandler();
1461 			// Should not be reached - a terminate handler is not expected to
1462 			// return.
1463 			abort();
1464 		}
1465 		unexpectedHandler();
1466 	}
1467 	/**
1468 	 * Returns whether there are any exceptions currently being thrown that
1469 	 * have not been caught.  This can occur inside a nested catch statement.
1470 	 */
1471 	bool uncaught_exception() throw()
1472 	{
1473 		__cxa_thread_info *info = thread_info();
1474 		return info->globals.uncaughtExceptions != 0;
1475 	}
1476 	/**
1477 	 * Returns the current unexpected handler.
1478 	 */
1479 	unexpected_handler get_unexpected() throw()
1480 	{
1481 		__cxa_thread_info *info = thread_info();
1482 		if (info->unexpectedHandler)
1483 		{
1484 			return info->unexpectedHandler;
1485 		}
1486 		return ATOMIC_LOAD(&unexpectedHandler);
1487 	}
1488 	/**
1489 	 * Returns the current terminate handler.
1490 	 */
1491 	terminate_handler get_terminate() throw()
1492 	{
1493 		__cxa_thread_info *info = thread_info();
1494 		if (info->terminateHandler)
1495 		{
1496 			return info->terminateHandler;
1497 		}
1498 		return ATOMIC_LOAD(&terminateHandler);
1499 	}
1500 }
1501 #if defined(__arm__) && !defined(__ARM_DWARF_EH__)
1502 extern "C" _Unwind_Exception *__cxa_get_cleanup(void)
1503 {
1504 	__cxa_thread_info *info = thread_info_fast();
1505 	_Unwind_Exception *exceptionObject = info->currentCleanup;
1506 	if (isCXXException(exceptionObject->exception_class))
1507 	{
1508 		__cxa_exception *ex =  exceptionFromPointer(exceptionObject);
1509 		ex->cleanupCount--;
1510 		if (ex->cleanupCount == 0)
1511 		{
1512 			info->currentCleanup = ex->nextCleanup;
1513 			ex->nextCleanup = 0;
1514 		}
1515 	}
1516 	else
1517 	{
1518 		info->currentCleanup = 0;
1519 	}
1520 	return exceptionObject;
1521 }
1522 
1523 asm (
1524 ".pushsection .text.__cxa_end_cleanup    \n"
1525 ".global __cxa_end_cleanup               \n"
1526 ".type __cxa_end_cleanup, \"function\"   \n"
1527 "__cxa_end_cleanup:                      \n"
1528 "	push {r1, r2, r3, r4}                \n"
1529 "	bl __cxa_get_cleanup                 \n"
1530 "	push {r1, r2, r3, r4}                \n"
1531 "	b _Unwind_Resume                     \n"
1532 "	bl abort                             \n"
1533 ".popsection                             \n"
1534 );
1535 #endif
1536