1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
|
/* Copyright (C) 2019-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef COMMON_SCOPE_EXIT_H
#define COMMON_SCOPE_EXIT_H
#include <functional>
#include <type_traits>
#include "gdbsupport/preprocessor.h"
/* scope_exit is a general-purpose scope guard that calls its exit
function at the end of the current scope. A scope_exit may be
canceled by calling the "release" method. The API is modeled on
P0052R5 - Generic Scope Guard and RAII Wrapper for the Standard
Library, which is itself based on Andrej Alexandrescu's
ScopeGuard/SCOPE_EXIT.
There are two forms available:
- The "make_scope_exit" form allows canceling the scope guard. Use
it like this:
auto cleanup = make_scope_exit ( <function, function object, lambda> );
...
cleanup.release (); // cancel
- If you don't need to cancel the guard, you can use the SCOPE_EXIT
macro, like this:
SCOPE_EXIT
{
// any code you like here.
}
See also forward_scope_exit.
*/
/* CRTP base class for cancelable scope_exit-like classes. Implements
the common call-custom-function-from-dtor functionality. Classes
that inherit this implement the on_exit() method, which is called
from scope_exit_base's dtor. */
template <typename CRTP>
class scope_exit_base
{
public:
scope_exit_base () = default;
~scope_exit_base ()
{
if (!m_released)
{
auto *self = static_cast<CRTP *> (this);
self->on_exit ();
}
}
/* This is needed for make_scope_exit because copy elision isn't
guaranteed until C++17. An optimizing compiler will usually skip
calling this, but it must exist. */
scope_exit_base (const scope_exit_base &other)
: m_released (other.m_released)
{
other.m_released = true;
}
void operator= (const scope_exit_base &) = delete;
/* If this is called, then the wrapped function will not be called
on destruction. */
void release () noexcept
{
m_released = true;
}
private:
/* True if released. Mutable because of the copy ctor hack
above. */
mutable bool m_released = false;
};
/* The scope_exit class. */
template<typename EF>
class scope_exit : public scope_exit_base<scope_exit<EF>>
{
/* For access to on_exit(). */
friend scope_exit_base<scope_exit<EF>>;
public:
template<typename EFP,
typename = gdb::Requires<std::is_constructible<EF, EFP>>>
scope_exit (EFP &&f)
try : m_exit_function ((!std::is_lvalue_reference<EFP>::value
&& std::is_nothrow_constructible<EF, EFP>::value)
? std::move (f)
: f)
{
}
catch (...)
{
/* "If the initialization of exit_function throws an exception,
calls f()." */
f ();
}
template<typename EFP,
typename = gdb::Requires<std::is_constructible<EF, EFP>>>
scope_exit (scope_exit &&rhs)
noexcept (std::is_nothrow_move_constructible<EF>::value
|| std::is_nothrow_copy_constructible<EF>::value)
: m_exit_function (std::is_nothrow_constructible<EFP>::value
? std::move (rhs)
: rhs)
{
rhs.release ();
}
/* This is needed for make_scope_exit because copy elision isn't
guaranteed until C++17. An optimizing compiler will usually skip
calling this, but it must exist. */
scope_exit (const scope_exit &other)
: scope_exit_base<scope_exit<EF>> (other),
m_exit_function (other.m_exit_function)
{
}
void operator= (const scope_exit &) = delete;
void operator= (scope_exit &&) = delete;
private:
void on_exit ()
{
m_exit_function ();
}
/* The function to call on scope exit. */
EF m_exit_function;
};
template <typename EF>
scope_exit<typename std::decay<EF>::type>
make_scope_exit (EF &&f)
{
return scope_exit<typename std::decay<EF>::type> (std::forward<EF> (f));
}
namespace detail
{
enum class scope_exit_lhs {};
template<typename EF>
scope_exit<typename std::decay<EF>::type>
operator+ (scope_exit_lhs, EF &&rhs)
{
return scope_exit<typename std::decay<EF>::type> (std::forward<EF> (rhs));
}
}
/* Register a block of code to run on scope exit. Note that the local
context is captured by reference, which means you should be careful
to avoid inadvertently changing a captured local's value before the
scope exit runs. */
#define SCOPE_EXIT \
auto CONCAT(scope_exit_, __LINE__) = ::detail::scope_exit_lhs () + [&] ()
#endif /* COMMON_SCOPE_EXIT_H */
|
