2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #ifndef FOLLY_DETAIL_UNCAUGHTEXCEPTIONCOUNTER_H_
18 #define FOLLY_DETAIL_UNCAUGHTEXCEPTIONCOUNTER_H_
22 #if defined(__GNUG__) || defined(__CLANG__)
23 #define FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS
24 namespace __cxxabiv1 {
25 // forward declaration (originally defined in unwind-cxx.h from from libstdc++)
26 struct __cxa_eh_globals;
27 // declared in cxxabi.h from libstdc++-v3
28 extern "C" __cxa_eh_globals* __cxa_get_globals() noexcept;
30 #elif defined(_MSC_VER) && (_MSC_VER >= 1400) && \
31 (_MSC_VER < 1900) // MSVC++ 8.0 or greater
32 #define FOLLY_EXCEPTION_COUNT_USE_GETPTD
33 // forward declaration (originally defined in mtdll.h from MSVCRT)
35 extern "C" _tiddata* _getptd(); // declared in mtdll.h from MSVCRT
36 #elif defined(_MSC_VER) && (_MSC_VER >= 1900) // MSVC++ 2015
37 #define FOLLY_EXCEPTION_COUNT_USE_STD
39 // Raise an error when trying to use this on unsupported platforms.
40 #error "Unsupported platform, don't include this header."
44 namespace folly { namespace detail {
47 * Used to check if a new uncaught exception was thrown by monitoring the
48 * number of uncaught exceptions.
51 * - create a new UncaughtExceptionCounter object
52 * - call isNewUncaughtException() on the new object to check if a new
53 * uncaught exception was thrown since the object was created
55 class UncaughtExceptionCounter {
57 UncaughtExceptionCounter() noexcept
58 : exceptionCount_(getUncaughtExceptionCount()) {}
60 UncaughtExceptionCounter(const UncaughtExceptionCounter& other) noexcept
61 : exceptionCount_(other.exceptionCount_) {}
63 bool isNewUncaughtException() noexcept {
64 return getUncaughtExceptionCount() > exceptionCount_;
68 int getUncaughtExceptionCount() noexcept;
74 * Returns the number of uncaught exceptions.
76 * This function is based on Evgeny Panasyuk's implementation from here:
77 * http://fburl.com/15190026
79 inline int UncaughtExceptionCounter::getUncaughtExceptionCount() noexcept {
80 #if defined(FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS)
81 // __cxa_get_globals returns a __cxa_eh_globals* (defined in unwind-cxx.h).
82 // The offset below returns __cxa_eh_globals::uncaughtExceptions.
83 return *(reinterpret_cast<unsigned int*>(static_cast<char*>(
84 static_cast<void*>(__cxxabiv1::__cxa_get_globals())) + sizeof(void*)));
85 #elif defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD)
86 // _getptd() returns a _tiddata* (defined in mtdll.h).
87 // The offset below returns _tiddata::_ProcessingThrow.
88 return *(reinterpret_cast<int*>(static_cast<char*>(
89 static_cast<void*>(_getptd())) + sizeof(void*) * 28 + 0x4 * 8));
90 #elif defined(FOLLY_EXCEPTION_COUNT_USE_STD)
91 return std::uncaught_exceptions();
97 #endif /* FOLLY_DETAIL_UNCAUGHTEXCEPTIONCOUNTER_H_ */