Mercurial > octave
view liboctave/util/unwind-prot.h @ 33584:3fe954c2fd25 default tip @
maint: merge stable to default
author | Rik <rik@octave.org> |
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date | Mon, 13 May 2024 11:41:11 -0700 |
parents | 4b601ca024d5 |
children |
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//////////////////////////////////////////////////////////////////////// // // Copyright (C) 1993-2024 The Octave Project Developers // // See the file COPYRIGHT.md in the top-level directory of this // distribution or <https://octave.org/copyright/>. // // This file is part of Octave. // // Octave 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. // // Octave 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 Octave; see the file COPYING. If not, see // <https://www.gnu.org/licenses/>. // //////////////////////////////////////////////////////////////////////// #if ! defined (octave_unwind_prot_h) #define octave_unwind_prot_h 1 #include "octave-config.h" #include <cstddef> #include <stack> #include <memory> #include "action-container.h" OCTAVE_BEGIN_NAMESPACE(octave) class OCTAVE_API unwind_protect : public action_container { public: unwind_protect () : m_lifo () { } OCTAVE_DISABLE_COPY_MOVE (unwind_protect) // Destructor should not raise an exception, so all actions // registered should be exception-safe. If you're not sure, see // unwind_protect_safe. ~unwind_protect () { run (); } operator bool () const { return ! empty (); } void run_first () { if (! empty ()) { // No leak on exception! std::unique_ptr<elem> ptr (m_lifo.top ()); m_lifo.pop (); ptr->run (); } } void discard_first () { if (! empty ()) { elem *ptr = m_lifo.top (); m_lifo.pop (); delete ptr; } } std::size_t size () const { return m_lifo.size (); } protected: virtual void add_action (elem *new_elem) { m_lifo.push (new_elem); } std::stack<elem *> m_lifo; }; // Like unwind_protect, but this one will guard against the possibility // of seeing an exception (or interrupt) in the cleanup actions. // Not that we can do much about it, but at least we won't crash. class OCTAVE_API unwind_protect_safe : public unwind_protect { private: void warn_unhandled_exception () const; public: unwind_protect_safe () : unwind_protect () { } OCTAVE_DISABLE_COPY_MOVE (unwind_protect_safe) ~unwind_protect_safe () { while (! empty ()) { try { run_first (); } catch (...) // Yes, the black hole. Remember we're in a destructor. { warn_unhandled_exception (); } } } }; // In most cases, the following are preferred for efficiency. Some // cases may require the flexibility of the general unwind_protect // mechanism defined above. // Perform action at end of the current scope when unwind_action // object destructor is called. // // For example: // // void fcn (int val) { ... } // // ... // // { // int val = 42; // // // template parameters, std::bind and std::function provide // // flexibility in calling forms (function pointer or lambda): // // unwind_action act1 (fcn, val); // unwind_action act2 ([val] () { fcn (val); }); // } // // NOTE: Don't forget to provide a name for the unwind_action // variable. If you write // // unwind_action /* NO NAME! */ (...); // // then the destructor for the temporary anonymous object will be // called immediately after the object is constructed instead of at // the end of the current scope. class OCTAVE_API unwind_action { public: unwind_action () : m_fcn () { } // FIXME: Do we need to apply std::forward to the arguments to // std::bind here? template <typename F, typename... Args> unwind_action (F&& fcn, Args&& ... args) : m_fcn (std::bind (fcn, args...)) { } OCTAVE_DISABLE_COPY_MOVE (unwind_action) ~unwind_action () { run (); } // FIXME: Do we need to apply std::forward to the arguments to // std::bind here? template <typename F, typename... Args> void set (F&& fcn, Args&& ... args) { m_fcn = std::bind (fcn, args...); } void set () { m_fcn = nullptr; } // Alias for set() which is clearer about programmer intention. void discard () { set (); } void run () { if (m_fcn) m_fcn (); // Invalidate so action won't run again when object is deleted. discard (); } private: std::function<void ()> m_fcn; }; // Like unwind_action, but this one will guard against the possibility // of seeing an exception (or interrupt) in the cleanup actions. // Not that we can do much about it, but at least we won't crash. class OCTAVE_API unwind_action_safe { private: void warn_unhandled_exception () const; public: unwind_action_safe () : m_fcn () { } // FIXME: Do we need to apply std::forward to the arguments to // std::bind here? template <typename F, typename... Args> unwind_action_safe (F&& fcn, Args&& ... args) : m_fcn (std::bind (fcn, args...)) { } OCTAVE_DISABLE_COPY_MOVE (unwind_action_safe) ~unwind_action_safe () { run (); } // FIXME: Do we need to apply std::forward to the arguments to // std::bind here? template <typename F, typename... Args> void set (F&& fcn, Args&& ... args) { m_fcn = std::bind (fcn, args...); } void set () { m_fcn = nullptr; } // Alias for set() which is clearer about programmer intention. void discard () { set (); } void run () { try { if (m_fcn) m_fcn (); } catch (...) // Yes, the black hole. Remember we're in a destructor. { warn_unhandled_exception (); } // Invalidate so action won't run again when object is deleted. discard (); } private: std::function<void ()> m_fcn; }; // Reset a variable value at the end of the current scope when // unwind_protect_var object destructor is called. // // For example: // // { // int x = 42; // unwind_protect_var<int> upv (x); // X will be reset at end of scope // x = 13; // Set temporary value. // } // // Temporary value may be set at construction: // // { // int x = ...; // unwind_protect_var<int> upv (x, 13); // X will be reset. // // temporary value is 13. // } // // NOTE: Don't forget to provide a name for the unwind_protect_var // variable. If you write // // unwind_protect_var<type> /* NO NAME! */ (...); // // then the destructor for the temporary anonymous object will be // called immediately after the object is constructed instead of at // the end of the current scope. // // FIXME: Once we are able to use C++17, class template argument // deduction will allow us to omit the explicit template type from the // constructor expression: // // unwind_protect_var upv (...); template <typename T> class unwind_protect_var { public: // Ensure that the value referenced by REF will be reset when this // unwind_protect_var object goes out of scope. explicit unwind_protect_var (T& ref) : m_ref (ref), m_val (ref) { } // Set the value referenced by REF to NEW_VAL and ensure that it // will be reset to its original value when this // unwind_protect_var object goes out of scope. unwind_protect_var (T& ref, const T& new_val) : m_ref (ref), m_val (ref) { m_ref = new_val; } OCTAVE_DISABLE_CONSTRUCT_COPY_MOVE (unwind_protect_var) ~unwind_protect_var () { m_ref = m_val; } private: T& m_ref; T m_val; }; OCTAVE_END_NAMESPACE(octave) #endif