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Remove meaningless namespace qualifier from throw override. Look up the Objective-C exception vtable dynamically (since weak import doesn't do what you think, even when it does). Remove useless debugging statements that were just causing trouble.

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This commit is contained in:
Gwynne Raskind 2015-06-22 10:12:16 -07:00 committed by Andreas Linde
parent 733eff9ac6
commit 4bc9d45c45
1 changed files with 22 additions and 21 deletions
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43
Classes/BITCrashCXXExceptionHandler.mm
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@ -54,23 +54,33 @@ static pthread_key_t _BITCrashCXXExceptionInfoTSDKey = 0;
@implementation BITCrashUncaughtCXXExceptionHandlerManager
extern "C" void LIBCXXABI_NORETURN __cxxabiv1::__cxa_throw(void *exception_object, std::type_info *tinfo, void (*dest)(void *))
extern "C" void LIBCXXABI_NORETURN __cxa_throw(void *exception_object, std::type_info *tinfo, void (*dest)(void *))
{
// Purposely do not take a lock in this function. The aim is to be as fast as
// possible. While we could really use some of the info set up by the real
// __cxa_throw, if we call through we never get control back - the function is
// noreturn and jumps to landing pads. Most of the stuff in __cxxabiv1 also
// won't work yet. We therefore have to do these checks by hand.
// This technique for distinguishing Objective-C exceptions is based on the
// The technique for distinguishing Objective-C exceptions is based on the
// implementation of objc_exception_throw(). It's weird, but it's fast. The
// weak import and NULL checks should guard against the implementation
// changing in a future version.
// explicit symbol load and NULL checks should guard against the
// implementation changing in a future version. (Or not existing in an earlier
// version).
// This works for C++ crashes in the main app but not yet in dynamic frameworks on iOS
extern const void WEAK_IMPORT_ATTRIBUTE *objc_ehtype_vtable[];
if (tinfo && objc_ehtype_vtable && // Guard from an ABI change
*reinterpret_cast<void **>(tinfo) == objc_ehtype_vtable + 2) {
typedef void (*cxa_throw_func)(void *, std::type_info *, void (*)(void *)) LIBCXXABI_NORETURN;
static dispatch_once_t predicate = 0;
static cxa_throw_func __original__cxa_throw = nullptr;
static const void **__real_objc_ehtype_vtable = nullptr;
dispatch_once(&predicate, ^ {
__original__cxa_throw = reinterpret_cast<cxa_throw_func>(dlsym(RTLD_NEXT, "__cxa_throw"));
__real_objc_ehtype_vtable = reinterpret_cast<const void **>(dlsym(RTLD_DEFAULT, "objc_ehtype_vtable"));
});
// Actually check for Objective-C exceptions.
if (tinfo && __real_objc_ehtype_vtable && // Guard from an ABI change
*reinterpret_cast<void **>(tinfo) == __real_objc_ehtype_vtable + 2) {
goto callthrough;
}
@ -92,13 +102,6 @@ extern "C" void LIBCXXABI_NORETURN __cxxabiv1::__cxa_throw(void *exception_objec
}
callthrough:
typedef void (*cxa_throw_func)(void *, std::type_info *, void (*)(void *)) LIBCXXABI_NORETURN;
static dispatch_once_t predicate = 0;
static cxa_throw_func __original__cxa_throw = nullptr;
dispatch_once(&predicate, ^ {
__original__cxa_throw = reinterpret_cast<cxa_throw_func>(dlsym(RTLD_NEXT, "__cxa_throw"));
});
if (__original__cxa_throw) {
__original__cxa_throw(exception_object, tinfo, dest);
} else {
@ -114,7 +117,7 @@ __attribute__((always_inline))
static inline void BITCrashIterateExceptionHandlers_unlocked(const BITCrashUncaughtCXXExceptionInfo &info)
{
for (const auto &handler : _BITCrashUncaughtExceptionHandlerList) {
handler(&info);
handler(&info);
}
}
@ -140,10 +143,8 @@ static void BITCrashUncaughtCXXTerminateHandler(void)
info.exception_frames_count = recorded_info->num_frames - 1;
info.exception_frames = &recorded_info->call_stack[1];
} else {
// There's no backtrace, grab this function's trace instead.
#if DEBUG
fprintf(stderr, "[HockeySDK] WARNING: No backtrace available, where did this exception come from?\n");
#endif
// There's no backtrace, grab this function's trace instead. Probably
// means the exception came from a dynamically loaded library.
void *frames[128] = { nullptr };
info.exception_frames_count = backtrace(&frames[0], sizeof(frames) / sizeof(frames[0])) - 1;