/*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-#ifndef FOLLY_SCOPEGUARD_H_
-#define FOLLY_SCOPEGUARD_H_
+#pragma once
#include <cstddef>
#include <functional>
#include <new>
+#include <type_traits>
+#include <utility>
+#include <folly/Portability.h>
#include <folly/Preprocessor.h>
#include <folly/detail/UncaughtExceptionCounter.h>
* a functor, or a void(*)() function pointer.
*
*
- * Usage example: Add a friend to memory iff it is also added to the db.
+ * Usage example: Add a friend to memory if and only if it is also added
+ * to the db.
*
* void User::addFriend(User& newFriend) {
* // add the friend to memory
dismissed_ = true;
}
+ template <typename T>
+ FOLLY_ALWAYS_INLINE static void runAndWarnAboutToCrashOnException(
+ T& function) noexcept {
+ try {
+ function();
+ } catch (...) {
+ warnAboutToCrash();
+ std::terminate();
+ }
+ }
+
protected:
- ScopeGuardImplBase()
- : dismissed_(false) {}
+ ScopeGuardImplBase() noexcept : dismissed_(false) {}
- ScopeGuardImplBase(ScopeGuardImplBase&& other) noexcept
- : dismissed_(other.dismissed_) {
- other.dismissed_ = true;
+ static ScopeGuardImplBase makeEmptyScopeGuard() noexcept {
+ return ScopeGuardImplBase{};
+ }
+
+ template <typename T>
+ static const T& asConst(const T& t) noexcept {
+ return t;
}
bool dismissed_;
+
+ private:
+ static void warnAboutToCrash() noexcept;
};
template <typename FunctionType>
class ScopeGuardImpl : public ScopeGuardImplBase {
public:
- explicit ScopeGuardImpl(const FunctionType& fn)
- : function_(fn) {}
-
- explicit ScopeGuardImpl(FunctionType&& fn)
- : function_(std::move(fn)) {}
-
- ScopeGuardImpl(ScopeGuardImpl&& other)
- : ScopeGuardImplBase(std::move(other))
- , function_(std::move(other.function_)) {
+ explicit ScopeGuardImpl(FunctionType& fn) noexcept(
+ std::is_nothrow_copy_constructible<FunctionType>::value)
+ : ScopeGuardImpl(
+ asConst(fn),
+ makeFailsafe(std::is_nothrow_copy_constructible<FunctionType>{},
+ &fn)) {}
+
+ explicit ScopeGuardImpl(const FunctionType& fn) noexcept(
+ std::is_nothrow_copy_constructible<FunctionType>::value)
+ : ScopeGuardImpl(
+ fn,
+ makeFailsafe(std::is_nothrow_copy_constructible<FunctionType>{},
+ &fn)) {}
+
+ explicit ScopeGuardImpl(FunctionType&& fn) noexcept(
+ std::is_nothrow_move_constructible<FunctionType>::value)
+ : ScopeGuardImpl(
+ std::move_if_noexcept(fn),
+ makeFailsafe(std::is_nothrow_move_constructible<FunctionType>{},
+ &fn)) {}
+
+ ScopeGuardImpl(ScopeGuardImpl&& other) noexcept(
+ std::is_nothrow_move_constructible<FunctionType>::value)
+ : function_(std::move_if_noexcept(other.function_)) {
+ // If the above line attempts a copy and the copy throws, other is
+ // left owning the cleanup action and will execute it (or not) depending
+ // on the value of other.dismissed_. The following lines only execute
+ // if the move/copy succeeded, in which case *this assumes ownership of
+ // the cleanup action and dismisses other.
+ dismissed_ = other.dismissed_;
+ other.dismissed_ = true;
}
~ScopeGuardImpl() noexcept {
}
private:
- void* operator new(size_t) = delete;
+ static ScopeGuardImplBase makeFailsafe(std::true_type, const void*) noexcept {
+ return makeEmptyScopeGuard();
+ }
- void execute() noexcept { function_(); }
+ template <typename Fn>
+ static auto makeFailsafe(std::false_type, Fn* fn) noexcept
+ -> ScopeGuardImpl<decltype(std::ref(*fn))> {
+ return ScopeGuardImpl<decltype(std::ref(*fn))>{std::ref(*fn)};
+ }
+
+ template <typename Fn>
+ explicit ScopeGuardImpl(Fn&& fn, ScopeGuardImplBase&& failsafe)
+ : ScopeGuardImplBase{}, function_(std::forward<Fn>(fn)) {
+ failsafe.dismiss();
+ }
+
+ void* operator new(std::size_t) = delete;
+
+ void execute() noexcept {
+ runAndWarnAboutToCrashOnException(function_);
+ }
FunctionType function_;
};
template <typename FunctionType>
ScopeGuardImpl<typename std::decay<FunctionType>::type>
-makeGuard(FunctionType&& fn) {
+makeGuard(FunctionType&& fn) noexcept(
+ std::is_nothrow_constructible<typename std::decay<FunctionType>::type,
+ FunctionType>::value) {
return ScopeGuardImpl<typename std::decay<FunctionType>::type>(
std::forward<FunctionType>(fn));
}
namespace detail {
#if defined(FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS) || \
- defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD)
+ defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD) || \
+ defined(FOLLY_EXCEPTION_COUNT_USE_STD)
/**
* ScopeGuard used for executing a function when leaving the current scope
* If the parameter is false, then the function is executed if no new uncaught
* exceptions are present at the end of the scope.
*
- * Used to implement SCOPE_FAIL and SCOPE_SUCCES below.
+ * Used to implement SCOPE_FAIL and SCOPE_SUCCESS below.
*/
template <typename FunctionType, bool executeOnException>
class ScopeGuardForNewException {
~ScopeGuardForNewException() noexcept(executeOnException) {
if (executeOnException == exceptionCounter_.isNewUncaughtException()) {
- function_();
+ if (executeOnException) {
+ ScopeGuardImplBase::runAndWarnAboutToCrashOnException(function_);
+ } else {
+ function_();
+ }
}
}
private:
ScopeGuardForNewException(const ScopeGuardForNewException& other) = delete;
- void* operator new(size_t) = delete;
+ void* operator new(std::size_t) = delete;
FunctionType function_;
UncaughtExceptionCounter exceptionCounter_;
}
} // namespace detail
-} // folly
+} // namespace folly
#define SCOPE_EXIT \
auto FB_ANONYMOUS_VARIABLE(SCOPE_EXIT_STATE) \
= ::folly::detail::ScopeGuardOnExit() + [&]() noexcept
#if defined(FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS) || \
- defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD)
+ defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD) || \
+ defined(FOLLY_EXCEPTION_COUNT_USE_STD)
#define SCOPE_FAIL \
auto FB_ANONYMOUS_VARIABLE(SCOPE_FAIL_STATE) \
= ::folly::detail::ScopeGuardOnFail() + [&]() noexcept
auto FB_ANONYMOUS_VARIABLE(SCOPE_SUCCESS_STATE) \
= ::folly::detail::ScopeGuardOnSuccess() + [&]()
#endif // native uncaught_exception() supported
-
-#endif // FOLLY_SCOPEGUARD_H_
projects / folly.git / blobdiff