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 */ 124