Extracted uncaught_exceptions function from Boost.Log.

The uncaught_exceptions function is functionally equivalent to unhandled_exceptions_count in Boost.Log and implements functionality similar to the same named C++17 standard function. Tests and docs are also included. One notable difference from std::uncaught_exceptions is that the return type is unsigned rather than signed. This is deliberate as uncaught_exceptions must never return a negative value and unsigned int better documents that. Theoretically, as a counter, it may also overflow.
2018-11-10 17:44:13 +03:00
parent d60775659b
commit 82957de970
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+/*
+ *             Copyright Andrey Semashev 2018.
+ * Distributed under the Boost Software License, Version 1.0.
+ *    (See accompanying file LICENSE_1_0.txt or copy at
+ *          https://www.boost.org/LICENSE_1_0.txt)
+ */
+/*!
+ * \file   uncaught_exceptions.hpp
+ * \author Andrey Semashev
+ * \date   2018-11-10
+ *
+ * \brief  This header provides an `uncaught_exception` function implementation, which was introduced in C++17.
+ *
+ * The code in this file is based on the implementation by Evgeny Panasyuk:
+ *
+ * https://github.com/panaseleus/stack_unwinding/blob/master/boost/exception/uncaught_exception_count.hpp
+ */
+
+#include <exception>
+#include <boost/config.hpp>
+
+#if defined(BOOST_HAS_PRAGMA_ONCE)
+#pragma once
+#endif
+
+namespace boost {
+
+namespace core {
+
+namespace detail {
+
+// cxxabi.h availability macro
+#if defined(__has_include) && (!defined(BOOST_GCC) || (__GNUC__ + 0) >= 5)
+#   if __has_include(<cxxabi.h>)
+#       define BOOST_CORE_HAS_CXXABI_H
+#   endif
+#elif defined(__GLIBCXX__) || defined(__GLIBCPP__)
+#   define BOOST_CORE_HAS_CXXABI_H
+#endif
+
+#if defined(__cpp_lib_uncaught_exceptions) && __cpp_lib_uncaught_exceptions >= 201411
+#define BOOST_CORE_HAS_UNCAUGHT_EXCEPTIONS
+#elif defined(BOOST_CORE_HAS_CXXABI_H)
+// MinGW GCC 4.4 seem to not work the same way the newer GCC versions do. As a result, __cxa_get_globals based implementation will always return 0.
+// Just disable it for now and fall back to std::uncaught_exception().
+#if !defined(__MINGW32__) || (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)))
+// Only GCC 4.7 declares __cxa_get_globals() in cxxabi.h, older compilers do not expose this function but it's there
+#define BOOST_CORE_HAS_CXA_GET_GLOBALS
+extern "C" void* __cxa_get_globals();
+#endif
+#elif defined(_MSC_VER)
+#if _MSC_VER >= 1900
+// Visual Studio 14 supports N4152 std::uncaught_exceptions()
+#define BOOST_CORE_HAS_UNCAUGHT_EXCEPTIONS
+#elif _MSC_VER >= 1400
+#define BOOST_CORE_HAS_GETPTD
+extern "C" void* _getptd();
+#endif
+#endif
+
+} // namespace detail
+
+#if !defined(BOOST_CORE_HAS_UNCAUGHT_EXCEPTIONS) && !defined(BOOST_CORE_HAS_CXA_GET_GLOBALS) && !defined(BOOST_CORE_HAS_GETPTD)
+//! This macro is defined when `uncaught_exceptions` is not guaranteed to return values greater than 1 if multiple exceptions are pending
+#define BOOST_CORE_UNCAUGHT_EXCEPTIONS_EMULATED
+#endif
+
+//! Returns the number of currently pending exceptions
+inline unsigned int uncaught_exceptions() BOOST_NOEXCEPT
+{
+#if defined(BOOST_CORE_HAS_UNCAUGHT_EXCEPTIONS)
+    // C++17 implementation
+    return static_cast< unsigned int >(std::uncaught_exceptions());
+#elif defined(BOOST_CORE_HAS_CXA_GET_GLOBALS)
+    // Tested on {clang 3.2,GCC 3.5.6,GCC 4.1.2,GCC 4.4.6,GCC 4.4.7}x{x32,x64}
+    return *(reinterpret_cast< const unsigned int* >(static_cast< const char* >(boost::core::detail::__cxa_get_globals()) + sizeof(void*))); // __cxa_eh_globals::uncaughtExceptions, x32 offset - 0x4, x64 - 0x8
+#elif defined(BOOST_CORE_HAS_GETPTD)
+    // MSVC specific. Tested on {MSVC2005SP1,MSVC2008SP1,MSVC2010SP1,MSVC2012}x{x32,x64}.
+    return *(reinterpret_cast< const unsigned int* >(static_cast< const char* >(boost::core::detail::_getptd()) + (sizeof(void*) == 8 ? 0x100 : 0x90))); // _tiddata::_ProcessingThrow, x32 offset - 0x90, x64 - 0x100
+#else
+    // Portable C++03 implementation. Does not allow to detect multiple nested exceptions.
+    return static_cast< unsigned int >(std::uncaught_exception());
+#endif
+}
+
+#undef BOOST_CORE_HAS_CXXABI_H
+#undef BOOST_CORE_HAS_CXA_GET_GLOBALS
+#undef BOOST_CORE_HAS_UNCAUGHT_EXCEPTIONS
+#undef BOOST_CORE_HAS_GETPTD
+
+} // namespace core
+
+} // namespace boost