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| 1 //===------------------------- cxa_exception.cpp --------------------------===// |
| 2 // |
| 3 // The LLVM Compiler Infrastructure |
| 4 // |
| 5 // This file is dual licensed under the MIT and the University of Illinois Open |
| 6 // Source Licenses. See LICENSE.TXT for details. |
| 7 // |
| 8 // |
| 9 // This file implements the "Exception Handling APIs" |
| 10 // http://www.codesourcery.com/public/cxx-abi/abi-eh.html |
| 11 // |
| 12 //===----------------------------------------------------------------------===// |
| 13 |
| 14 #include "cxxabi.h" |
| 15 |
| 16 #include <exception> // for std::terminate |
| 17 #include <cstdlib> // for malloc, free |
| 18 #include <cstring> // for memset |
| 19 #include <pthread.h> |
| 20 |
| 21 #include "cxa_exception.hpp" |
| 22 #include "cxa_handlers.hpp" |
| 23 |
| 24 // +---------------------------+-----------------------------+---------------+ |
| 25 // | __cxa_exception | _Unwind_Exception CLNGC++\0 | thrown object | |
| 26 // +---------------------------+-----------------------------+---------------+ |
| 27 // ^ |
| 28 // | |
| 29 // +-------------------------------------------------------+ |
| 30 // | |
| 31 // +---------------------------+-----------------------------+ |
| 32 // | __cxa_dependent_exception | _Unwind_Exception CLNGC++\1 | |
| 33 // +---------------------------+-----------------------------+ |
| 34 |
| 35 namespace __cxxabiv1 { |
| 36 |
| 37 #pragma GCC visibility push(default) |
| 38 |
| 39 // Utility routines |
| 40 static |
| 41 inline |
| 42 __cxa_exception* |
| 43 cxa_exception_from_thrown_object(void* thrown_object) |
| 44 { |
| 45 return static_cast<__cxa_exception*>(thrown_object) - 1; |
| 46 } |
| 47 |
| 48 // Note: This is never called when exception_header is masquerading as a |
| 49 // __cxa_dependent_exception. |
| 50 static |
| 51 inline |
| 52 void* |
| 53 thrown_object_from_cxa_exception(__cxa_exception* exception_header) |
| 54 { |
| 55 return static_cast<void*>(exception_header + 1); |
| 56 } |
| 57 |
| 58 // Get the exception object from the unwind pointer. |
| 59 // Relies on the structure layout, where the unwind pointer is right in |
| 60 // front of the user's exception object |
| 61 static |
| 62 inline |
| 63 __cxa_exception* |
| 64 cxa_exception_from_exception_unwind_exception(_Unwind_Exception* unwind_exceptio
n) |
| 65 { |
| 66 return cxa_exception_from_thrown_object(unwind_exception + 1 ); |
| 67 } |
| 68 |
| 69 static |
| 70 inline |
| 71 size_t |
| 72 cxa_exception_size_from_exception_thrown_size(size_t size) |
| 73 { |
| 74 return size + sizeof (__cxa_exception); |
| 75 } |
| 76 |
| 77 static void setExceptionClass(_Unwind_Exception* unwind_exception) { |
| 78 unwind_exception->exception_class = kOurExceptionClass; |
| 79 } |
| 80 |
| 81 static void setDependentExceptionClass(_Unwind_Exception* unwind_exception) { |
| 82 unwind_exception->exception_class = kOurDependentExceptionClass; |
| 83 } |
| 84 |
| 85 // Is it one of ours? |
| 86 static bool isOurExceptionClass(const _Unwind_Exception* unwind_exception) { |
| 87 return (unwind_exception->exception_class & get_vendor_and_language) == |
| 88 (kOurExceptionClass & get_vendor_and_language); |
| 89 } |
| 90 |
| 91 static bool isDependentException(_Unwind_Exception* unwind_exception) { |
| 92 return (unwind_exception->exception_class & 0xFF) == 0x01; |
| 93 } |
| 94 |
| 95 // This does not need to be atomic |
| 96 static inline int incrementHandlerCount(__cxa_exception *exception) { |
| 97 return ++exception->handlerCount; |
| 98 } |
| 99 |
| 100 // This does not need to be atomic |
| 101 static inline int decrementHandlerCount(__cxa_exception *exception) { |
| 102 return --exception->handlerCount; |
| 103 } |
| 104 |
| 105 #include "fallback_malloc.ipp" |
| 106 |
| 107 // Allocate some memory from _somewhere_ |
| 108 static void *do_malloc(size_t size) { |
| 109 void *ptr = std::malloc(size); |
| 110 if (NULL == ptr) // if malloc fails, fall back to emergency stash |
| 111 ptr = fallback_malloc(size); |
| 112 return ptr; |
| 113 } |
| 114 |
| 115 static void do_free(void *ptr) { |
| 116 is_fallback_ptr(ptr) ? fallback_free(ptr) : std::free(ptr); |
| 117 } |
| 118 |
| 119 /* |
| 120 If reason isn't _URC_FOREIGN_EXCEPTION_CAUGHT, then the terminateHandler |
| 121 stored in exc is called. Otherwise the exceptionDestructor stored in |
| 122 exc is called, and then the memory for the exception is deallocated. |
| 123 |
| 124 This is never called for a __cxa_dependent_exception. |
| 125 */ |
| 126 static |
| 127 void |
| 128 exception_cleanup_func(_Unwind_Reason_Code reason, _Unwind_Exception* unwind_exc
eption) |
| 129 { |
| 130 __cxa_exception* exception_header = cxa_exception_from_exception_unwind_exce
ption(unwind_exception); |
| 131 if (_URC_FOREIGN_EXCEPTION_CAUGHT != reason) |
| 132 std::__terminate(exception_header->terminateHandler); |
| 133 // Just in case there exists a dependent exception that is pointing to this, |
| 134 // check the reference count and only destroy this if that count goes to
zero. |
| 135 __cxa_decrement_exception_refcount(unwind_exception + 1); |
| 136 } |
| 137 |
| 138 static LIBCXXABI_NORETURN void failed_throw(__cxa_exception* exception_header) { |
| 139 // Section 2.5.3 says: |
| 140 // * For purposes of this ABI, several things are considered exception hand
lers: |
| 141 // ** A terminate() call due to a throw. |
| 142 // and |
| 143 // * Upon entry, Following initialization of the catch parameter, |
| 144 // a handler must call: |
| 145 // * void *__cxa_begin_catch(void *exceptionObject ); |
| 146 (void) __cxa_begin_catch(&exception_header->unwindHeader); |
| 147 std::__terminate(exception_header->terminateHandler); |
| 148 } |
| 149 |
| 150 extern "C" { |
| 151 |
| 152 // Allocate a __cxa_exception object, and zero-fill it. |
| 153 // Reserve "thrown_size" bytes on the end for the user's exception |
| 154 // object. Zero-fill the object. If memory can't be allocated, call |
| 155 // std::terminate. Return a pointer to the memory to be used for the |
| 156 // user's exception object. |
| 157 void * __cxa_allocate_exception (size_t thrown_size) throw() { |
| 158 size_t actual_size = cxa_exception_size_from_exception_thrown_size(thrown_si
ze); |
| 159 __cxa_exception* exception_header = static_cast<__cxa_exception*>(do_malloc(
actual_size)); |
| 160 if (NULL == exception_header) |
| 161 std::terminate(); |
| 162 std::memset(exception_header, 0, actual_size); |
| 163 return thrown_object_from_cxa_exception(exception_header); |
| 164 } |
| 165 |
| 166 |
| 167 // Free a __cxa_exception object allocated with __cxa_allocate_exception. |
| 168 void __cxa_free_exception (void * thrown_object) throw() { |
| 169 do_free(cxa_exception_from_thrown_object(thrown_object)); |
| 170 } |
| 171 |
| 172 |
| 173 // This function shall allocate a __cxa_dependent_exception and |
| 174 // return a pointer to it. (Really to the object, not past its' end). |
| 175 // Otherwise, it will work like __cxa_allocate_exception. |
| 176 void * __cxa_allocate_dependent_exception () { |
| 177 size_t actual_size = sizeof(__cxa_dependent_exception); |
| 178 void *ptr = do_malloc(actual_size); |
| 179 if (NULL == ptr) |
| 180 std::terminate(); |
| 181 std::memset(ptr, 0, actual_size); |
| 182 return ptr; |
| 183 } |
| 184 |
| 185 |
| 186 // This function shall free a dependent_exception. |
| 187 // It does not affect the reference count of the primary exception. |
| 188 void __cxa_free_dependent_exception (void * dependent_exception) { |
| 189 do_free(dependent_exception); |
| 190 } |
| 191 |
| 192 |
| 193 // 2.4.3 Throwing the Exception Object |
| 194 /* |
| 195 After constructing the exception object with the throw argument value, |
| 196 the generated code calls the __cxa_throw runtime library routine. This |
| 197 routine never returns. |
| 198 |
| 199 The __cxa_throw routine will do the following: |
| 200 |
| 201 * Obtain the __cxa_exception header from the thrown exception object address, |
| 202 which can be computed as follows: |
| 203 __cxa_exception *header = ((__cxa_exception *) thrown_exception - 1); |
| 204 * Save the current unexpected_handler and terminate_handler in the __cxa_excepti
on header. |
| 205 * Save the tinfo and dest arguments in the __cxa_exception header. |
| 206 * Set the exception_class field in the unwind header. This is a 64-bit value |
| 207 representing the ASCII string "XXXXC++\0", where "XXXX" is a |
| 208 vendor-dependent string. That is, for implementations conforming to this |
| 209 ABI, the low-order 4 bytes of this 64-bit value will be "C++\0". |
| 210 * Increment the uncaught_exception flag. |
| 211 * Call _Unwind_RaiseException in the system unwind library, Its argument is the |
| 212 pointer to the thrown exception, which __cxa_throw itself received as an argumen
t. |
| 213 __Unwind_RaiseException begins the process of stack unwinding, described |
| 214 in Section 2.5. In special cases, such as an inability to find a |
| 215 handler, _Unwind_RaiseException may return. In that case, __cxa_throw |
| 216 will call terminate, assuming that there was no handler for the |
| 217 exception. |
| 218 */ |
| 219 LIBCXXABI_NORETURN |
| 220 void |
| 221 __cxa_throw(void* thrown_object, std::type_info* tinfo, void (*dest)(void*)) |
| 222 { |
| 223 __cxa_eh_globals *globals = __cxa_get_globals(); |
| 224 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_
object); |
| 225 |
| 226 exception_header->unexpectedHandler = std::get_unexpected(); |
| 227 exception_header->terminateHandler = std::get_terminate(); |
| 228 exception_header->exceptionType = tinfo; |
| 229 exception_header->exceptionDestructor = dest; |
| 230 setExceptionClass(&exception_header->unwindHeader); |
| 231 exception_header->referenceCount = 1; // This is a newly allocated exceptio
n, no need for thread safety. |
| 232 globals->uncaughtExceptions += 1; // Not atomically, since globals are thr
ead-local |
| 233 |
| 234 exception_header->unwindHeader.exception_cleanup = exception_cleanup_func; |
| 235 #if __arm__ |
| 236 _Unwind_SjLj_RaiseException(&exception_header->unwindHeader); |
| 237 #else |
| 238 _Unwind_RaiseException(&exception_header->unwindHeader); |
| 239 #endif |
| 240 // This only happens when there is no handler, or some unexpected unwinding |
| 241 // error happens. |
| 242 failed_throw(exception_header); |
| 243 } |
| 244 |
| 245 |
| 246 // 2.5.3 Exception Handlers |
| 247 /* |
| 248 The adjusted pointer is computed by the personality routine during phase 1 |
| 249 and saved in the exception header (either __cxa_exception or |
| 250 __cxa_dependent_exception). |
| 251 |
| 252 Requires: exception is native |
| 253 */ |
| 254 void* |
| 255 __cxa_get_exception_ptr(void* unwind_exception) throw() |
| 256 { |
| 257 return cxa_exception_from_exception_unwind_exception |
| 258 ( |
| 259 static_cast<_Unwind_Exception*>(unwind_exception) |
| 260 )->adjustedPtr; |
| 261 } |
| 262 |
| 263 /* |
| 264 This routine can catch foreign or native exceptions. If native, the exception |
| 265 can be a primary or dependent variety. This routine may remain blissfully |
| 266 ignorant of whether the native exception is primary or dependent. |
| 267 |
| 268 If the exception is native: |
| 269 * Increment's the exception's handler count. |
| 270 * Push the exception on the stack of currently-caught exceptions if it is not |
| 271 already there (from a rethrow). |
| 272 * Decrements the uncaught_exception count. |
| 273 * Returns the adjusted pointer to the exception object, which is stored in |
| 274 the __cxa_exception by the personality routine. |
| 275 |
| 276 If the exception is foreign, this means it did not originate from one of throw |
| 277 routines. The foreign exception does not necessarily have a __cxa_exception |
| 278 header. However we can catch it here with a catch (...), or with a call |
| 279 to terminate or unexpected during unwinding. |
| 280 * Do not try to increment the exception's handler count, we don't know where |
| 281 it is. |
| 282 * Push the exception on the stack of currently-caught exceptions only if the |
| 283 stack is empty. The foreign exception has no way to link to the current |
| 284 top of stack. If the stack is not empty, call terminate. Even with an |
| 285 empty stack, this is hacked in by pushing a pointer to an imaginary |
| 286 __cxa_exception block in front of the foreign exception. It would be better |
| 287 if the __cxa_eh_globals structure had a stack of _Unwind_Exception, but it |
| 288 doesn't. It has a stack of __cxa_exception (which has a next* in it). |
| 289 * Do not decrement the uncaught_exception count because we didn't increment it |
| 290 in __cxa_throw (or one of our rethrow functions). |
| 291 * If we haven't terminated, assume the exception object is just past the |
| 292 _Unwind_Exception and return a pointer to that. |
| 293 */ |
| 294 void* |
| 295 __cxa_begin_catch(void* unwind_arg) throw() |
| 296 { |
| 297 _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(unwind
_arg); |
| 298 bool native_exception = isOurExceptionClass(unwind_exception); |
| 299 __cxa_eh_globals* globals = __cxa_get_globals(); |
| 300 // exception_header is a hackish offset from a foreign exception, but it |
| 301 // works as long as we're careful not to try to access any __cxa_exception |
| 302 // parts. |
| 303 __cxa_exception* exception_header = |
| 304 cxa_exception_from_exception_unwind_exception |
| 305 ( |
| 306 static_cast<_Unwind_Exception*>(unwind_exception) |
| 307 ); |
| 308 if (native_exception) |
| 309 { |
| 310 // Increment the handler count, removing the flag about being rethrown |
| 311 exception_header->handlerCount = exception_header->handlerCount < 0 ? |
| 312 -exception_header->handlerCount + 1 : exception_header->handlerCount
+ 1; |
| 313 // place the exception on the top of the stack if it's not already |
| 314 // there by a previous rethrow |
| 315 if (exception_header != globals->caughtExceptions) |
| 316 { |
| 317 exception_header->nextException = globals->caughtExceptions; |
| 318 globals->caughtExceptions = exception_header; |
| 319 } |
| 320 globals->uncaughtExceptions -= 1; // Not atomically, since globals are
thread-local |
| 321 return exception_header->adjustedPtr; |
| 322 } |
| 323 // Else this is a foreign exception |
| 324 // If the caughtExceptions stack is not empty, terminate |
| 325 if (globals->caughtExceptions != 0) |
| 326 std::terminate(); |
| 327 // Push the foreign exception on to the stack |
| 328 globals->caughtExceptions = exception_header; |
| 329 return unwind_exception + 1; |
| 330 } |
| 331 |
| 332 |
| 333 /* |
| 334 Upon exit for any reason, a handler must call: |
| 335 void __cxa_end_catch (); |
| 336 |
| 337 This routine can be called for either a native or foreign exception. |
| 338 For a native exception: |
| 339 * Locates the most recently caught exception and decrements its handler count. |
| 340 * Removes the exception from the caught exception stack, if the handler count go
es to zero. |
| 341 * If the handler count goes down to zero, and the exception was not re-thrown |
| 342 by throw, it locates the primary exception (which may be the same as the one |
| 343 it's handling) and decrements its reference count. If that reference count |
| 344 goes to zero, the function destroys the exception. In any case, if the current |
| 345 exception is a dependent exception, it destroys that. |
| 346 |
| 347 For a foreign exception: |
| 348 * If it has been rethrown, there is nothing to do. |
| 349 * Otherwise delete the exception and pop the catch stack to empty. |
| 350 */ |
| 351 void __cxa_end_catch() |
| 352 { |
| 353 static_assert(sizeof(__cxa_exception) == sizeof(__cxa_dependent_exception), |
| 354 "sizeof(__cxa_exception) must be equal to sizeof(__cxa_depende
nt_exception)"); |
| 355 __cxa_eh_globals* globals = __cxa_get_globals_fast(); // __cxa_get_globals c
alled in __cxa_begin_catch |
| 356 __cxa_exception* exception_header = globals->caughtExceptions; |
| 357 // If we've rethrown a foreign exception, then globals->caughtExceptions |
| 358 // will have been made an empty stack by __cxa_rethrow() and there is |
| 359 // nothing more to be done. Do nothing! |
| 360 if (NULL != exception_header) |
| 361 { |
| 362 bool native_exception = isOurExceptionClass(&exception_header->unwindHea
der); |
| 363 if (native_exception) |
| 364 { |
| 365 // This is a native exception |
| 366 if (exception_header->handlerCount < 0) |
| 367 { |
| 368 // The exception has been rethrown by __cxa_rethrow, so don't d
elete it |
| 369 if (0 == incrementHandlerCount(exception_header)) |
| 370 { |
| 371 // Remove from the chain of uncaught exceptions |
| 372 globals->caughtExceptions = exception_header->nextException; |
| 373 // but don't destroy |
| 374 } |
| 375 // Keep handlerCount negative in case there are nested catch's |
| 376 // that need to be told that this exception is rethrown. Don'
t |
| 377 // erase this rethrow flag until the exception is recaught. |
| 378 } |
| 379 else |
| 380 { |
| 381 // The native exception has not been rethrown |
| 382 if (0 == decrementHandlerCount(exception_header)) |
| 383 { |
| 384 // Remove from the chain of uncaught exceptions |
| 385 globals->caughtExceptions = exception_header->nextException; |
| 386 // Destroy this exception, being careful to distinguish |
| 387 // between dependent and primary exceptions |
| 388 if (isDependentException(&exception_header->unwindHeader)) |
| 389 { |
| 390 // Reset exception_header to primaryException and deallo
cate the dependent exception |
| 391 __cxa_dependent_exception* dep_exception_header = |
| 392 reinterpret_cast<__cxa_dependent_exception*>(excepti
on_header); |
| 393 exception_header = |
| 394 cxa_exception_from_thrown_object(dep_exception_heade
r->primaryException); |
| 395 __cxa_free_dependent_exception(dep_exception_header); |
| 396 } |
| 397 // Destroy the primary exception only if its referenceCount
goes to 0 |
| 398 // (this decrement must be atomic) |
| 399 __cxa_decrement_exception_refcount(thrown_object_from_cxa_ex
ception(exception_header)); |
| 400 } |
| 401 } |
| 402 } |
| 403 else |
| 404 { |
| 405 // The foreign exception has not been rethrown. Pop the stack |
| 406 // and delete it. If there are nested catch's and they try |
| 407 // to touch a foreign exception in any way, that is undefined |
| 408 // behavior. They likely can't since the only way to catch |
| 409 // a foreign exception is with catch (...)! |
| 410 _Unwind_DeleteException(&globals->caughtExceptions->unwindHeader); |
| 411 globals->caughtExceptions = 0; |
| 412 } |
| 413 } |
| 414 } |
| 415 |
| 416 // Note: exception_header may be masquerading as a __cxa_dependent_exception |
| 417 // and that's ok. exceptionType is there too. |
| 418 // However watch out for foreign exceptions. Return null for them. |
| 419 std::type_info * __cxa_current_exception_type() { |
| 420 // get the current exception |
| 421 __cxa_eh_globals *globals = __cxa_get_globals_fast(); |
| 422 if (NULL == globals) |
| 423 return NULL; // If there have never been any exceptions, there are
none now. |
| 424 __cxa_exception *exception_header = globals->caughtExceptions; |
| 425 if (NULL == exception_header) |
| 426 return NULL; // No current exception |
| 427 if (!isOurExceptionClass(&exception_header->unwindHeader)) |
| 428 return NULL; |
| 429 return exception_header->exceptionType; |
| 430 } |
| 431 |
| 432 // 2.5.4 Rethrowing Exceptions |
| 433 /* This routine can rethrow native or foreign exceptions. |
| 434 If the exception is native: |
| 435 * marks the exception object on top of the caughtExceptions stack |
| 436 (in an implementation-defined way) as being rethrown. |
| 437 * If the caughtExceptions stack is empty, it calls terminate() |
| 438 (see [C++FDIS] [except.throw], 15.1.8). |
| 439 * It then calls _Unwind_RaiseException which should not return |
| 440 (terminate if it does). |
| 441 Note: exception_header may be masquerading as a __cxa_dependent_exception |
| 442 and that's ok. |
| 443 */ |
| 444 LIBCXXABI_NORETURN |
| 445 void |
| 446 __cxa_rethrow() |
| 447 { |
| 448 __cxa_eh_globals* globals = __cxa_get_globals(); |
| 449 __cxa_exception* exception_header = globals->caughtExceptions; |
| 450 if (NULL == exception_header) |
| 451 std::terminate(); // throw; called outside of a exception handler |
| 452 bool native_exception = isOurExceptionClass(&exception_header->unwindHeader)
; |
| 453 if (native_exception) |
| 454 { |
| 455 // Mark the exception as being rethrown (reverse the effects of __cxa_b
egin_catch) |
| 456 exception_header->handlerCount = -exception_header->handlerCount; |
| 457 globals->uncaughtExceptions += 1; |
| 458 // __cxa_end_catch will remove this exception from the caughtExceptions
stack if necessary |
| 459 } |
| 460 else // this is a foreign exception |
| 461 { |
| 462 // The only way to communicate to __cxa_end_catch that we've rethrown |
| 463 // a foreign exception, so don't delete us, is to pop the stack here |
| 464 // which must be empty afterwards. Then __cxa_end_catch will do |
| 465 // nothing |
| 466 globals->caughtExceptions = 0; |
| 467 } |
| 468 #if __arm__ |
| 469 _Unwind_SjLj_RaiseException(&exception_header->unwindHeader); |
| 470 #else |
| 471 _Unwind_RaiseException(&exception_header->unwindHeader); |
| 472 #endif |
| 473 |
| 474 // If we get here, some kind of unwinding error has occurred. |
| 475 // There is some weird code generation bug happening with |
| 476 // Apple clang version 4.0 (tags/Apple/clang-418.0.2) (based on LLVM 3.1
svn) |
| 477 // If we call failed_throw here. Turns up with -O2 or higher, and -Os. |
| 478 __cxa_begin_catch(&exception_header->unwindHeader); |
| 479 if (native_exception) |
| 480 std::__terminate(exception_header->terminateHandler); |
| 481 // Foreign exception: can't get exception_header->terminateHandler |
| 482 std::terminate(); |
| 483 } |
| 484 |
| 485 /* |
| 486 If thrown_object is not null, atomically increment the referenceCount field |
| 487 of the __cxa_exception header associated with the thrown object referred to |
| 488 by thrown_object. |
| 489 |
| 490 Requires: If thrown_object is not NULL, it is a native exception. |
| 491 */ |
| 492 void |
| 493 __cxa_increment_exception_refcount(void* thrown_object) throw() |
| 494 { |
| 495 if (thrown_object != NULL ) |
| 496 { |
| 497 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thr
own_object); |
| 498 __sync_add_and_fetch(&exception_header->referenceCount, 1); |
| 499 } |
| 500 } |
| 501 |
| 502 /* |
| 503 If thrown_object is not null, atomically decrement the referenceCount field |
| 504 of the __cxa_exception header associated with the thrown object referred to |
| 505 by thrown_object. If the referenceCount drops to zero, destroy and |
| 506 deallocate the exception. |
| 507 |
| 508 Requires: If thrown_object is not NULL, it is a native exception. |
| 509 */ |
| 510 void |
| 511 __cxa_decrement_exception_refcount(void* thrown_object) throw() |
| 512 { |
| 513 if (thrown_object != NULL ) |
| 514 { |
| 515 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thr
own_object); |
| 516 if (__sync_sub_and_fetch(&exception_header->referenceCount, size_t(1)) =
= 0) |
| 517 { |
| 518 if (NULL != exception_header->exceptionDestructor) |
| 519 exception_header->exceptionDestructor(thrown_object); |
| 520 __cxa_free_exception(thrown_object); |
| 521 } |
| 522 } |
| 523 } |
| 524 |
| 525 /* |
| 526 Returns a pointer to the thrown object (if any) at the top of the |
| 527 caughtExceptions stack. Atomically increment the exception's referenceCount
. |
| 528 If there is no such thrown object or if the thrown object is foreign, |
| 529 returns null. |
| 530 |
| 531 We can use __cxa_get_globals_fast here to get the globals because if there h
ave |
| 532 been no exceptions thrown, ever, on this thread, we can return NULL without |
| 533 the need to allocate the exception-handling globals. |
| 534 */ |
| 535 void* |
| 536 __cxa_current_primary_exception() throw() |
| 537 { |
| 538 // get the current exception |
| 539 __cxa_eh_globals* globals = __cxa_get_globals_fast(); |
| 540 if (NULL == globals) |
| 541 return NULL; // If there are no globals, there is no exception |
| 542 __cxa_exception* exception_header = globals->caughtExceptions; |
| 543 if (NULL == exception_header) |
| 544 return NULL; // No current exception |
| 545 if (!isOurExceptionClass(&exception_header->unwindHeader)) |
| 546 return NULL; // Can't capture a foreign exception (no way to refc
ount it) |
| 547 if (isDependentException(&exception_header->unwindHeader)) { |
| 548 __cxa_dependent_exception* dep_exception_header = |
| 549 reinterpret_cast<__cxa_dependent_exception*>(exception_header); |
| 550 exception_header = cxa_exception_from_thrown_object(dep_exception_header
->primaryException); |
| 551 } |
| 552 void* thrown_object = thrown_object_from_cxa_exception(exception_header); |
| 553 __cxa_increment_exception_refcount(thrown_object); |
| 554 return thrown_object; |
| 555 } |
| 556 |
| 557 /* |
| 558 If reason isn't _URC_FOREIGN_EXCEPTION_CAUGHT, then the terminateHandler |
| 559 stored in exc is called. Otherwise the referenceCount stored in the |
| 560 primary exception is decremented, destroying the primary if necessary. |
| 561 Finally the dependent exception is destroyed. |
| 562 */ |
| 563 static |
| 564 void |
| 565 dependent_exception_cleanup(_Unwind_Reason_Code reason, _Unwind_Exception* unwin
d_exception) |
| 566 { |
| 567 __cxa_dependent_exception* dep_exception_header = |
| 568 reinterpret_cast<__cxa_dependent_exception*>(unwind_except
ion + 1) - 1; |
| 569 if (_URC_FOREIGN_EXCEPTION_CAUGHT != reason) |
| 570 std::__terminate(dep_exception_header->terminateHandler); |
| 571 __cxa_decrement_exception_refcount(dep_exception_header->primaryException); |
| 572 __cxa_free_dependent_exception(dep_exception_header); |
| 573 } |
| 574 |
| 575 /* |
| 576 If thrown_object is not null, allocate, initialize and throw a dependent |
| 577 exception. |
| 578 */ |
| 579 void |
| 580 __cxa_rethrow_primary_exception(void* thrown_object) |
| 581 { |
| 582 if ( thrown_object != NULL ) |
| 583 { |
| 584 // thrown_object guaranteed to be native because |
| 585 // __cxa_current_primary_exception returns NULL for foreign exceptions |
| 586 __cxa_exception* exception_header = cxa_exception_from_thrown_object(thr
own_object); |
| 587 __cxa_dependent_exception* dep_exception_header = |
| 588 static_cast<__cxa_dependent_exception*>(__cxa_allocate_dependent_exc
eption()); |
| 589 dep_exception_header->primaryException = thrown_object; |
| 590 __cxa_increment_exception_refcount(thrown_object); |
| 591 dep_exception_header->exceptionType = exception_header->exceptionType; |
| 592 dep_exception_header->unexpectedHandler = std::get_unexpected(); |
| 593 dep_exception_header->terminateHandler = std::get_terminate(); |
| 594 setDependentExceptionClass(&dep_exception_header->unwindHeader); |
| 595 __cxa_get_globals()->uncaughtExceptions += 1; |
| 596 dep_exception_header->unwindHeader.exception_cleanup = dependent_excepti
on_cleanup; |
| 597 #if __arm__ |
| 598 _Unwind_SjLj_RaiseException(&dep_exception_header->unwindHeader); |
| 599 #else |
| 600 _Unwind_RaiseException(&dep_exception_header->unwindHeader); |
| 601 #endif |
| 602 // Some sort of unwinding error. Note that terminate is a handler. |
| 603 __cxa_begin_catch(&dep_exception_header->unwindHeader); |
| 604 } |
| 605 // If we return client will call terminate() |
| 606 } |
| 607 |
| 608 bool |
| 609 __cxa_uncaught_exception() throw() |
| 610 { |
| 611 // This does not report foreign exceptions in flight |
| 612 __cxa_eh_globals* globals = __cxa_get_globals_fast(); |
| 613 if (globals == 0) |
| 614 return false; |
| 615 return globals->uncaughtExceptions != 0; |
| 616 } |
| 617 |
| 618 } // extern "C" |
| 619 |
| 620 #pragma GCC visibility pop |
| 621 |
| 622 } // abi |
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