Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.
PrevUpHomeNext

Safe hooks

Features of the safe mode
Configuring safe-mode assertions

Boost.Intrusive hooks can be configured to operate in safe-link mode. The safe mode is activated by default, but it can be also explicitly activated:

//Configuring explicity the safe mode
class Foo : public list_base_hook< link_mode<safe_link> >
{};

Thanks to the safe-mode the user can detect without any external reference, if the object is actually inserted in a container. Let's review the basic features of the safe-mode:

  • Hooks' constructor puts the hook in a well-known default state.
  • Hooks' destructor checks if the hook is in the well-known default state. If not, an assertion is raised.
  • Every time an object is being inserted in the intrusive container, the container checks if the hook is in the well-known default state. If not, an assertion is raised.
  • Every time an object is being erased from the intrusive container, the container puts the erased object in the well-known default state.

With these features, without any external reference the user can know if the object has been inserted in a container calling the is_linked() member function. If the object is not actually inserted in a container, the hook is in the default state and if it's inserted in a container, the hook is not in the default state.

By default, all safe-mode assertions raised by Boost-Intrusive hooks and containers in are implemented using BOOST_ASSERT, which can be configured by the user. See http://www.boost.org/libs/utility/assert.html for more information about BOOST_ASSERT.

BOOST_ASSERT is globally configured, so the user might want to redefine intrusive safe-mode assertions without modifying the global BOOST_ASSERT. This can be achieved redefining the following macros:

  • BOOST_INTRUSIVE_SAFE_HOOK_DEFAULT_ASSERT: This assertion will be used in insertion functions of the intrusive containers to check that the hook of the value to be inserted is default constructed.
  • BOOST_INTRUSIVE_SAFE_HOOK_DESTRUCTOR_ASSERT: This assertion will be used in hooks' destructors to check that the hook is in a default state.

If any of these macros is not redefined, the assertion will be defaul to BOOST_ASSERT.


PrevUpHomeNext