117 lines
3.7 KiB
C++
117 lines
3.7 KiB
C++
/**
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* Copyright 2004-present, Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <atomic>
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#include <stdexcept>
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#include <cxxabi.h>
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#include <unwind.h>
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#include <cassert>
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#include <lyra/lyra_exceptions.h>
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namespace facebook {
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namespace lyra {
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namespace {
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std::atomic<bool> enableBacktraces{true};
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}
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void enableCxaThrowHookBacktraces(bool enable) {
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enableBacktraces.store(enable, std::memory_order_relaxed);
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}
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[[gnu::noreturn]] void (*original_cxa_throw)(void*, const std::type_info*, void (*) (void *));
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#if defined(_LIBCPP_VERSION)
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[[noreturn]] void cxa_throw(void* obj, const std::type_info* type, void (*destructor) (void *)) {
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// lyra doesn't have support yet for libc++.
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original_cxa_throw(obj, type, destructor);
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}
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#else
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using namespace detail;
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namespace {
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const auto traceHolderType =
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static_cast<const abi::__class_type_info*>(&typeid(ExceptionTraceHolder));
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// lyra's __cxa_throw attaches stack trace information to thrown exceptions. It basically does:
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// 1. capture stack trace
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// 2. construct a new type_info struct that:
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// a. holds the ExceptionTraceHolder
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// b. supports upcasting to lyra::ExceptionTraceHolder* (by just returning the holder member)
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// c. acts like the original exception type_info otherwise
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// 3. call original __cxa_throw() with original exception pointer, the
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// HijackedExceptionTypeInfo, and HijackedExceptionTypeInfo::destructor
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// (which will both delete the constructed type info and call the original
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// destructor).
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struct HijackedExceptionTypeInfo : public abi::__class_type_info {
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HijackedExceptionTypeInfo(void* obj, const std::type_info* base, void(*destructor)(void*))
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: abi::__class_type_info{base->name()}, base_{base}, orig_dest_{destructor} {
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}
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bool __is_pointer_p() const override {
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return base_->__is_pointer_p();
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}
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bool __is_function_p() const override {
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return base_->__is_function_p();
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}
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bool __do_catch(const type_info *__thr_type, void **__thr_obj, unsigned __outer) const override {
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return base_->__do_catch(__thr_type, __thr_obj, __outer);
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}
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bool __do_upcast(const abi::__class_type_info *__target, void **__obj_ptr) const override {
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if (__target == traceHolderType) {
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*__obj_ptr = (void*)&stack_;
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return true;
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}
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return base_->__do_upcast(__target, __obj_ptr);
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}
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static void destructor(void* obj) {
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auto exc_ptr = reinterpret_cast<std::exception_ptr*>(&obj);
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auto info = reinterpret_cast<const::std::type_info*>(exc_ptr->__cxa_exception_type());
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auto mutable_info = static_cast<HijackedExceptionTypeInfo*>(const_cast<std::type_info*>(info));
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mutable_info->orig_dest_(obj);
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delete mutable_info;
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}
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private:
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const std::type_info* base_;
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void (*orig_dest_)(void*);
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ExceptionTraceHolder stack_;
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};
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} // namespace
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[[noreturn]] void cxa_throw(void* obj, const std::type_info* type, void (*destructor) (void *)) {
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if (enableBacktraces.load(std::memory_order_relaxed)) {
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if (!type->__do_upcast(traceHolderType, &obj)) {
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type = new HijackedExceptionTypeInfo(obj, type, destructor);
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destructor = HijackedExceptionTypeInfo::destructor;
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}
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}
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original_cxa_throw(obj, type, destructor);
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}
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#endif // libc++
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} // namespace lyra
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} // namespace facebook
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