1 /* Copyright (C) 2019 Free Software Foundation, Inc.
3 This file is part of GDB.
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 #ifndef COMMON_SCOPE_EXIT_H
19 #define COMMON_SCOPE_EXIT_H
22 #include <type_traits>
23 #include "common/preprocessor.h"
25 /* scope_exit is a general-purpose scope guard that calls its exit
26 function at the end of the current scope. A scope_exit may be
27 canceled by calling the "release" method. The API is modeled on
28 P0052R5 - Generic Scope Guard and RAII Wrapper for the Standard
29 Library, which is itself based on Andrej Alexandrescu's
30 ScopeGuard/SCOPE_EXIT.
32 There are two forms available:
34 - The "make_scope_exit" form allows canceling the scope guard. Use
37 auto cleanup = make_scope_exit ( <function, function object, lambda> );
39 cleanup.release (); // cancel
41 - If you don't need to cancel the guard, you can use the SCOPE_EXIT
46 // any code you like here.
49 See also forward_scope_exit.
52 /* CRTP base class for cancelable scope_exit-like classes. Implements
53 the common call-custom-function-from-dtor functionality. Classes
54 that inherit this implement the on_exit() method, which is called
55 from scope_exit_base's dtor. */
57 template <typename CRTP>
61 scope_exit_base () = default;
67 auto *self = static_cast<CRTP *> (this);
72 /* This is needed for make_scope_exit because copy elision isn't
73 guaranteed until C++17. An optimizing compiler will usually skip
74 calling this, but it must exist. */
75 scope_exit_base (const scope_exit_base &other)
76 : m_released (other.m_released)
78 other.m_released = true;
81 void operator= (const scope_exit_base &) = delete;
83 /* If this is called, then the wrapped function will not be called
85 void release () noexcept
92 /* True if released. Mutable because of the copy ctor hack
94 mutable bool m_released = false;
97 /* The scope_exit class. */
100 class scope_exit : public scope_exit_base<scope_exit<EF>>
102 /* For access to on_exit(). */
103 friend scope_exit_base<scope_exit<EF>>;
107 template<typename EFP,
108 typename = gdb::Requires<std::is_constructible<EF, EFP>>>
110 try : m_exit_function ((!std::is_lvalue_reference<EFP>::value
111 && std::is_nothrow_constructible<EF, EFP>::value)
118 /* "If the initialization of exit_function throws an exception,
123 template<typename EFP,
124 typename = gdb::Requires<std::is_constructible<EF, EFP>>>
125 scope_exit (scope_exit &&rhs)
126 noexcept (std::is_nothrow_move_constructible<EF>::value
127 || std::is_nothrow_copy_constructible<EF>::value)
128 : m_exit_function (std::is_nothrow_constructible<EFP>::value
135 /* This is needed for make_scope_exit because copy elision isn't
136 guaranteed until C++17. An optimizing compiler will usually skip
137 calling this, but it must exist. */
138 scope_exit (const scope_exit &other)
139 : scope_exit_base<scope_exit<EF>> (other),
140 m_exit_function (other.m_exit_function)
144 void operator= (const scope_exit &) = delete;
145 void operator= (scope_exit &&) = delete;
153 /* The function to call on scope exit. */
157 template <typename EF>
158 scope_exit<typename std::decay<EF>::type>
159 make_scope_exit (EF &&f)
161 return scope_exit<typename std::decay<EF>::type> (std::forward<EF> (f));
167 enum class scope_exit_lhs {};
169 template<typename EF>
170 scope_exit<typename std::decay<EF>::type>
171 operator+ (scope_exit_lhs, EF &&rhs)
173 return scope_exit<typename std::decay<EF>::type> (std::forward<EF> (rhs));
178 /* Register a block of code to run on scope exit. Note that the local
179 context is captured by reference, which means you should be careful
180 to avoid inadvertently changing a captured local's value before the
184 auto CONCAT(scope_exit_, __LINE__) = ::detail::scope_exit_lhs () + [&] ()
186 #endif /* COMMON_SCOPE_EXIT_H */