| 1 | /* Copyright (C) 2019-2020 Free Software Foundation, Inc. |
| 2 | |
| 3 | This file is part of GDB. |
| 4 | |
| 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. |
| 9 | |
| 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. |
| 14 | |
| 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/>. */ |
| 17 | |
| 18 | #ifndef COMMON_FORWARD_SCOPE_EXIT_H |
| 19 | #define COMMON_FORWARD_SCOPE_EXIT_H |
| 20 | |
| 21 | #include "gdbsupport/scope-exit.h" |
| 22 | #include <functional> |
| 23 | |
| 24 | /* A forward_scope_exit is like scope_exit, but instead of giving it a |
| 25 | callable, you instead specialize it for a given cleanup function, |
| 26 | and the generated class automatically has a constructor with the |
| 27 | same interface as the cleanup function. forward_scope_exit |
| 28 | captures the arguments passed to the ctor, and in turn passes those |
| 29 | as arguments to the wrapped cleanup function, when it is called at |
| 30 | scope exit time, from within the forward_scope_exit dtor. The |
| 31 | forward_scope_exit class can take any number of arguments, and is |
| 32 | cancelable if needed. |
| 33 | |
| 34 | This allows usage like this: |
| 35 | |
| 36 | void |
| 37 | delete_longjmp_breakpoint (int arg) |
| 38 | { |
| 39 | // Blah, blah, blah... |
| 40 | } |
| 41 | |
| 42 | using longjmp_breakpoint_cleanup |
| 43 | = FORWARD_SCOPE_EXIT (delete_longjmp_breakpoint); |
| 44 | |
| 45 | This above created a new cleanup class `longjmp_breakpoint_cleanup` |
| 46 | than can then be used like this: |
| 47 | |
| 48 | longjmp_breakpoint_cleanup obj (thread); |
| 49 | |
| 50 | // Blah, blah, blah... |
| 51 | |
| 52 | obj.release (); // Optional cancel if needed. |
| 53 | |
| 54 | forward_scope_exit is also handy when you would need to wrap a |
| 55 | scope_exit in a gdb::optional: |
| 56 | |
| 57 | gdb::optional<longjmp_breakpoint_cleanup> cleanup; |
| 58 | if (some condition) |
| 59 | cleanup.emplace (thread); |
| 60 | ... |
| 61 | if (cleanup) |
| 62 | cleanup->release (); |
| 63 | |
| 64 | since with scope exit, you would have to know the scope_exit's |
| 65 | callable template type when you create the gdb::optional: |
| 66 | |
| 67 | gdb:optional<scope_exit<what goes here?>> |
| 68 | |
| 69 | The "forward" naming fits both purposes shown above -- the class |
| 70 | "forwards" ctor arguments to the wrapped cleanup function at scope |
| 71 | exit time, and can also be used to "forward declare" |
| 72 | scope_exit-like objects. */ |
| 73 | |
| 74 | namespace detail |
| 75 | { |
| 76 | |
| 77 | /* Function and Signature are passed in the same type, in order to |
| 78 | extract Function's arguments' types in the specialization below. |
| 79 | Those are used to generate the constructor. */ |
| 80 | |
| 81 | template<typename Function, Function *function, typename Signature> |
| 82 | struct forward_scope_exit; |
| 83 | |
| 84 | template<typename Function, Function *function, |
| 85 | typename Res, typename... Args> |
| 86 | class forward_scope_exit<Function, function, Res (Args...)> |
| 87 | : public scope_exit_base<forward_scope_exit<Function, |
| 88 | function, |
| 89 | Res (Args...)>> |
| 90 | { |
| 91 | /* For access to on_exit(). */ |
| 92 | friend scope_exit_base<forward_scope_exit<Function, |
| 93 | function, |
| 94 | Res (Args...)>>; |
| 95 | |
| 96 | public: |
| 97 | explicit forward_scope_exit (Args ...args) |
| 98 | : m_bind_function (function, args...) |
| 99 | { |
| 100 | /* Nothing. */ |
| 101 | } |
| 102 | |
| 103 | private: |
| 104 | void on_exit () |
| 105 | { |
| 106 | m_bind_function (); |
| 107 | } |
| 108 | |
| 109 | /* The function and the arguments passed to the ctor, all packed in |
| 110 | a std::bind. */ |
| 111 | decltype (std::bind (function, std::declval<Args> ()...)) |
| 112 | m_bind_function; |
| 113 | }; |
| 114 | |
| 115 | } /* namespace detail */ |
| 116 | |
| 117 | /* This is the "public" entry point. It's a macro to avoid having to |
| 118 | name FUNC more than once. */ |
| 119 | |
| 120 | #define FORWARD_SCOPE_EXIT(FUNC) \ |
| 121 | detail::forward_scope_exit<decltype (FUNC), FUNC, decltype (FUNC)> |
| 122 | |
| 123 | #endif /* COMMON_FORWARD_SCOPE_EXIT_H */ |