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// ------------------------------------------------------------------------
//
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 1998 - 2025 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Part of the source code is dual licensed under Apache-2.0 WITH
// LLVM-exception OR LGPL-2.1-or-later. Detailed license information
// governing the source code and code contributions can be found in
// LICENSE.md and CONTRIBUTING.md at the top level directory of deal.II.
//
// ------------------------------------------------------------------------
#include <deal.II/base/enable_observer_pointer.h>
#include <deal.II/base/exceptions.h>
#include <deal.II/base/logstream.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <typeinfo>
DEAL_II_NAMESPACE_OPEN
static const char *unknown_subscriber = "unknown subscriber";
std::mutex EnableObserverPointer::mutex;
EnableObserverPointer::EnableObserverPointer(
EnableObserverPointer &&subscriptor) noexcept
: counter(0)
, object_info(subscriptor.object_info)
{
for (auto *const validity_ptr : subscriptor.validity_pointers)
*validity_ptr = false;
subscriptor.validity_pointers.clear();
}
EnableObserverPointer::~EnableObserverPointer()
{
for (auto *const validity_ptr : validity_pointers)
*validity_ptr = false;
object_info = nullptr;
}
void
EnableObserverPointer::check_no_subscribers() const noexcept
{
// Check whether there are still subscriptions to this object. If so, output
// the actual name of the class to which this object belongs, i.e. the most
// derived class. Note that the name may be mangled, so it need not be the
// clear-text class name. However, you can obtain the latter by running the
// c++filt program over the output.
if constexpr (running_in_debug_mode())
{
// If there are still active pointers, show a message and kill the
// program. However, under some circumstances, this is not so desirable.
// For example, in code like this:
//
// Triangulation tria;
// DoFHandler *dh = new DoFHandler(tria);
// ...some function that throws an exception
//
// the exception will lead to the destruction of the triangulation, but
// since the dof_handler is on the heap it will not be destroyed. This
// will trigger an assertion in the triangulation. If we kill the program
// at this point, we will never be able to learn what caused the problem.
// In this situation, just display a message and continue the program.
if (counter != 0)
{
if (std::uncaught_exceptions() == 0)
{
std::string infostring;
for (const auto &map_entry : counter_map)
{
if (map_entry.second > 0)
infostring +=
"\n from Subscriber " + std::string(map_entry.first);
}
if (infostring.empty())
infostring = "<none>";
AssertNothrow(counter == 0,
ExcInUse(counter.load(),
object_info->name(),
infostring));
}
else
{
std::cerr
<< "---------------------------------------------------------"
<< std::endl
<< "An object pointed to by a ObserverPointer is being destroyed."
<< std::endl
<< "Under normal circumstances, this would abort the program."
<< std::endl
<< "However, another exception is being processed at the"
<< std::endl
<< "moment, so the program will continue to run to allow"
<< std::endl
<< "this exception to be processed." << std::endl
<< "---------------------------------------------------------"
<< std::endl;
}
}
}
}
EnableObserverPointer &
EnableObserverPointer::operator=(EnableObserverPointer &&s) noexcept
{
for (auto *const validity_ptr : s.validity_pointers)
*validity_ptr = false;
s.validity_pointers.clear();
object_info = s.object_info;
return *this;
}
void
EnableObserverPointer::subscribe(std::atomic<bool> *const validity,
const std::string &id) const
{
std::lock_guard<std::mutex> lock(mutex);
if (object_info == nullptr)
object_info = &typeid(*this);
++counter;
const std::string &name = id.empty() ? unknown_subscriber : id;
++counter_map[name];
*validity = true;
validity_pointers.push_back(validity);
}
void
EnableObserverPointer::unsubscribe(std::atomic<bool> *const validity,
const std::string &id) const
{
const std::string &name = id.empty() ? unknown_subscriber : id;
if (counter == 0)
{
AssertNothrow(counter > 0, ExcNoSubscriber(object_info->name(), name));
// This is for the case that we do not abort after the exception
return;
}
std::lock_guard<std::mutex> lock(mutex);
map_iterator it = counter_map.find(name);
if (it == counter_map.end())
{
AssertNothrow(it != counter_map.end(),
ExcNoSubscriber(object_info->name(), name));
// This is for the case that we do not abort after the exception
return;
}
if (it->second == 0)
{
AssertNothrow(it->second > 0, ExcNoSubscriber(object_info->name(), name));
// This is for the case that we do not abort after the exception
return;
}
auto validity_ptr_it =
std::find(validity_pointers.begin(), validity_pointers.end(), validity);
if (validity_ptr_it == validity_pointers.end())
{
AssertNothrow(
validity_ptr_it != validity_pointers.end(),
ExcMessage(
"This EnableObserverPointer object does not know anything about the supplied pointer!"));
return;
}
validity_pointers.erase(validity_ptr_it);
--counter;
--it->second;
}
void
EnableObserverPointer::list_subscribers() const
{
list_subscribers(deallog);
}
DEAL_II_NAMESPACE_CLOSE
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