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// *****************************************************************************
// * This file is part of the FreeFileSync project. It is distributed under *
// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0 *
// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
// *****************************************************************************
#ifndef SCOPE_GUARD_H_8971632487321434
#define SCOPE_GUARD_H_8971632487321434
#include <cassert>
#include <exception>
#include "type_tools.h"
//std::uncaught_exceptions() currently unsupported on GCC and Clang => clean up ASAP
static_assert(__GNUC__ < 7 || (__GNUC__ == 7 && (__GNUC_MINOR__ < 2 || (__GNUC_MINOR__ == 2 && __GNUC_PATCHLEVEL__ <= 1))), "check std::uncaught_exceptions support");
namespace __cxxabiv1
{
struct __cxa_eh_globals;
extern "C" __cxa_eh_globals* __cxa_get_globals() noexcept;
}
inline
int getUncaughtExceptionCount()
{
return *(reinterpret_cast<unsigned int*>(static_cast<char*>(static_cast<void*>(__cxxabiv1::__cxa_get_globals())) + sizeof(void*)));
}
//best of Zen, Loki and C++17
namespace zen
{
//Scope Guard
/*
auto guardAio = zen::makeGuard<ScopeGuardRunMode::ON_EXIT>([&] { ::CloseHandle(hDir); });
...
guardAio.dismiss();
Scope Exit:
ZEN_ON_SCOPE_EXIT(::CloseHandle(hDir));
ZEN_ON_SCOPE_FAIL(UndoPreviousWork());
ZEN_ON_SCOPE_SUCCESS(NotifySuccess());
*/
enum class ScopeGuardRunMode
{
ON_EXIT,
ON_SUCCESS,
ON_FAIL
};
//partially specialize scope guard destructor code and get rid of those pesky MSVC "4127 conditional expression is constant"
template <typename F> inline
void runScopeGuardDestructor(F& fun, int /*exeptionCountOld*/, StaticEnum<ScopeGuardRunMode, ScopeGuardRunMode::ON_EXIT>)
{
try { fun(); }
catch (...) { assert(false); } //consistency: don't expect exceptions for ON_EXIT even if "!failed"!
}
template <typename F> inline
void runScopeGuardDestructor(F& fun, int exeptionCountOld, StaticEnum<ScopeGuardRunMode, ScopeGuardRunMode::ON_SUCCESS>)
{
const bool failed = getUncaughtExceptionCount() > exeptionCountOld;
if (!failed)
fun(); //throw X
}
template <typename F> inline
void runScopeGuardDestructor(F& fun, int exeptionCountOld, StaticEnum<ScopeGuardRunMode, ScopeGuardRunMode::ON_FAIL>)
{
const bool failed = getUncaughtExceptionCount() > exeptionCountOld;
if (failed)
try { fun(); }
catch (...) { assert(false); }
}
template <ScopeGuardRunMode runMode, typename F>
class ScopeGuard
{
public:
explicit ScopeGuard(const F& fun) : fun_(fun) {}
explicit ScopeGuard( F&& fun) : fun_(std::move(fun)) {}
ScopeGuard(ScopeGuard&& other) : fun_(std::move(other.fun_)),
exeptionCount_(other.exeptionCount_),
dismissed_(other.dismissed_) { other.dismissed_ = true; }
~ScopeGuard() noexcept(runMode != ScopeGuardRunMode::ON_SUCCESS)
{
if (!dismissed_)
runScopeGuardDestructor(fun_, exeptionCount_, StaticEnum<ScopeGuardRunMode, runMode>());
}
void dismiss() { dismissed_ = true; }
private:
ScopeGuard (const ScopeGuard&) = delete;
ScopeGuard& operator=(const ScopeGuard&) = delete;
F fun_;
const int exeptionCount_ = getUncaughtExceptionCount();
bool dismissed_ = false;
};
template <ScopeGuardRunMode runMode, class F> inline
auto makeGuard(F&& fun) { return ScopeGuard<runMode, std::decay_t<F>>(std::forward<F>(fun)); }
}
#define ZEN_CONCAT_SUB(X, Y) X ## Y
#define ZEN_CONCAT(X, Y) ZEN_CONCAT_SUB(X, Y)
#define ZEN_ON_SCOPE_EXIT(X) auto ZEN_CONCAT(dummy, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_EXIT >([&]{ X; }); (void)ZEN_CONCAT(dummy, __LINE__);
#define ZEN_ON_SCOPE_FAIL(X) auto ZEN_CONCAT(dummy, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_FAIL >([&]{ X; }); (void)ZEN_CONCAT(dummy, __LINE__);
#define ZEN_ON_SCOPE_SUCCESS(X) auto ZEN_CONCAT(dummy, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_SUCCESS>([&]{ X; }); (void)ZEN_CONCAT(dummy, __LINE__);
#endif //SCOPE_GUARD_H_8971632487321434
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