UncaughtExceptions.h

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/*
 * Copyright 2013-present Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <exception>

#if !defined(FOLLY_FORCE_EXCEPTION_COUNT_USE_STD) && \
    (defined(__GNUG__) || defined(__clang__))
#define FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS
namespace __cxxabiv1 {
// forward declaration (originally defined in unwind-cxx.h from from libstdc++)
struct __cxa_eh_globals;
// declared in cxxabi.h from libstdc++-v3
extern "C" __cxa_eh_globals* __cxa_get_globals() noexcept;
} // namespace __cxxabiv1
#elif defined(_MSC_VER) && (_MSC_VER >= 1400) && \
    (_MSC_VER < 1900) // MSVC++ 8.0 or greater
#define FOLLY_EXCEPTION_COUNT_USE_GETPTD
// forward declaration (originally defined in mtdll.h from MSVCRT)
struct _tiddata;
extern "C" _tiddata* _getptd(); // declared in mtdll.h from MSVCRT
#elif defined(FOLLY_FORCE_EXCEPTION_COUNT_USE_STD) || \
    (defined(_MSC_VER) && (_MSC_VER >= 1900)) // MSVC++ 2015
#define FOLLY_EXCEPTION_COUNT_USE_STD
#else
// Raise an error when trying to use this on unsupported platforms.
#error "Unsupported platform, don't include this header."
#endif

namespace folly {

inline int uncaught_exceptions() noexcept {
#if defined(FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS)
  // __cxa_get_globals returns a __cxa_eh_globals* (defined in unwind-cxx.h).
  // The offset below returns __cxa_eh_globals::uncaughtExceptions.
  return *(reinterpret_cast<unsigned int*>(
      static_cast<char*>(static_cast<void*>(__cxxabiv1::__cxa_get_globals())) +
      sizeof(void*)));
#elif defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD)
  // _getptd() returns a _tiddata* (defined in mtdll.h).
  // The offset below returns _tiddata::_ProcessingThrow.
  return *(reinterpret_cast<int*>(
      static_cast<char*>(static_cast<void*>(_getptd())) + sizeof(void*) * 28 +
      0x4 * 8));
#elif defined(FOLLY_EXCEPTION_COUNT_USE_STD)
  return std::uncaught_exceptions();
#endif
}

} // namespace folly