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exceptionhandler.cc

// -*- c++ -*-
/* $Id: exceptionhandler.cc 4 2005-05-13 20:47:18Z taybin $ */

/* exceptionhandler.cc
 *
 * Copyright 2002 The gtkmm Development Team
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <glib.h>
#include <exception>
#include <list>

#include <glibmmconfig.h>
#include <glibmm/error.h>
#include <glibmm/exceptionhandler.h>
#include <glibmm/thread.h>

GLIBMM_USING_STD(exception)
GLIBMM_USING_STD(list)


namespace
{

typedef sigc::signal<void> HandlerList;

// Each thread has its own list of exception handlers
// to avoid thread synchronization problems.
static Glib::StaticPrivate<HandlerList> thread_specific_handler_list = GLIBMM_STATIC_PRIVATE_INIT;


static void glibmm_exception_warning(const GError* error)
{
  g_assert(error != 0);

  g_critical("\n"
      "unhandled exception (type Glib::Error) in signal handler:\n"
      "domain: %s\n"
      "code  : %d\n"
      "what  : %s\n",
      g_quark_to_string(error->domain), error->code,
      (error->message) ? error->message : "(null)");
}

static void glibmm_unexpected_exception()
{
  try
  {
    throw; // re-throw current exception
  }
  catch(const Glib::Error& error)
  {
    // Access the GError directly, to avoid possible exceptions from C++ code.
    glibmm_exception_warning(error.gobj());

    // For most failures that cause a Glib::Error exception, aborting the
    // program seems too harsh.  Instead, give control back to the main loop.
    return;
  }
  catch(const std::exception& except)
  {
    g_error("\n"
        "unhandled exception (type std::exception) in signal handler:\n"
        "what: %s\n", except.what());
  }
  catch(...)
  {
    g_error("\nunhandled exception (type unknown) in signal handler\n");
  }
}

} // anonymous namespace


namespace Glib
{

sigc::connection add_exception_handler(const sigc::slot<void>& slot)
{
  HandlerList* handler_list = thread_specific_handler_list.get();

  if(!handler_list)
  {
    handler_list = new HandlerList();
    thread_specific_handler_list.set(handler_list);
  }

  handler_list->slots().push_front(slot);
  return handler_list->slots().begin();
}

// internal
void exception_handlers_invoke() throw()
{
  // This function will be called from our GLib signal handler proxies
  // if an exception has been caught.  It's not possible to throw C++
  // exceptions through C signal handlers.  To handle this situation, the
  // programmer can install slots to global Reusable Exception Handlers.
  //
  // A handler has to re-throw the current exception in a try block, and then
  // catch the exceptions it knows about.  Any unknown exceptions should just
  // fall through, i.e. the handler must not do catch(...).
  //
  // We now invoke each of the installed slots until the exception has been
  // handled.  If there are no more handlers in the list and the exception
  // is still unhandled, call glibmm_unexpected_exception().

  if(HandlerList *const handler_list = thread_specific_handler_list.get())
  {
    HandlerList::iterator pslot = handler_list->slots().begin();

    while(pslot != handler_list->slots().end())
    {
      // Calling an empty slot would mean ignoring the exception,
      // thus we have to check for dead slots explicitly.
      if(pslot->empty())
      {
        pslot = handler_list->slots().erase(pslot);
        continue;
      }

      // Call the Reusable Exception Handler, which should re-throw
      // the exception that's currently on the stack.
      try
      {
        (*pslot)();
      }
      catch(...) // unhandled, try next slot
      {
        ++pslot;
        continue;
      }

      // The exception has either been handled or ignored.
      // Give control back to the GLib main loop.
      return;
    }
  }

  // Critical: The exception is still unhandled.
  glibmm_unexpected_exception();
}

} // namespace Glib


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