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## History

#### Version 4.0.0 - boost 1.53

Deprecated features:

| Warning
Deprecated features since boost 1.53 will be available only until boost 1.58.

- C++11 compliance: packaged_task<R> is deprecated, use instead packaged_task<R()>. See BOOST_THREAD_PROVIDES_SIGNATURE_PACKAGED_TASK and BOOST_THREAD_DONT_PROVIDE_SIGNATURE_PACKAGED_TASK
- #7537 deprecate Mutex::scoped_lock and scoped_try_lock and boost::condition

New Features:

- #6270 c++11 compliance: Add thread constructor from movable callable and movable arguments Provided when BOOST_THREAD_PROVIDES_VARIADIC_THREAD is defined (Default value from Boost 1.55): See BOOST_THREAD_PROVIDES_VARIADIC_THREAD and BOOST_THREAD_DONT_PROVIDE_VARIADIC_THREAD.
- #7279 C++11 compliance: Add noexcept in system related functions
- #7280 C++11 compliance: Add promise::...at_thread_exit functions
- #7281 C++11 compliance: Add ArgTypes to packaged_task template. Provided when BOOST_THREAD_PROVIDES_SIGNATURE_PACKAGED_TASK is defined (Default value from Boost 1.55). See BOOST_THREAD_PROVIDES_SIGNATURE_PACKAGED_TASK and BOOST_THREAD_DONT_PROVIDE_SIGNATURE_PACKAGED_TASK.
- #7282 C++11 compliance: Add packaged_task::make_ready_at_thread_exit function
- #7412 C++11 compliance: Add async from movable callable and movable arguments Provided when BOOST_THREAD_PROVIDES_VARIADIC_THREAD and BOOST_THREAD_PROVIDES_SIGNATURE_PACKAGED_TASK are defined (Default value from Boost 1.55): See BOOST_THREAD_PROVIDES_SIGNATURE_PACKAGED_TASK and BOOST_THREAD_DONT_PROVIDE_SIGNATURE_PACKAGED_TASK, BOOST_THREAD_PROVIDES_VARIADIC_THREAD and BOOST_THREAD_DONT_PROVIDE_VARIADIC_THREAD.
- #7413 C++11 compliance: Add async when the launch policy is deferred.
- #7414 C++11 compliance: future::get post-condition should be valid()==false.
- #7422 Provide a condition variable with zero-overhead performance penality.
- #7444 Async: Add make_future/make_shared_future.
- #7540 Threads: Add a helper class that join a thread on destruction.
- #7541 Threads: Add a thread wrapper class that joins on destruction.
- #7575 C++11 compliance: A future created by async should "join" in the destructor.
- #7587 Synchro: Add strict_lock and nested_strict_lock.
- #7588 Synchro: Split the locks.hpp in several files to limit dependencies.
- #7590 Synchro: Add lockable concept checkers based on Boost.ConceptCheck.
- #7591 Add lockable traits that can be used with enable_if.
- #7592 Synchro: Add a null_mutex that is a no-op and that is a model of UpgardeLockable.
- #7593 Synchro: Add a externally_locked class.
- #7594 Threads: Allow to disable thread interruptions.

Fixed Bugs:

- #7464 BOOST_TEST(n_alive == 1); fails due to race condition in a regression test tool.
- #7657 Serious performance and memory consumption hit if condition_variable methods condition notify_one or notify_all is used repeatedly.
- #7665 this_thread::sleep_for no longer uses steady_clock in thread.
- #7668 thread_group::join_all() should check whether its threads are joinable.
- #7669 thread_group::join_all() should catch resource_deadlock_would_occur.
- #7672 lockable_traits.hpp syntax error: "defined" token misspelled.
- #7798 boost::future set_wait_callback thread safety issues.
- #7808 Incorrect description of effects for this_thread::sleep_for and this_thread::sleep_until.
- #7812 Returns: cv_status::no_timeout if the call is returning because the time period specified by rel_time has elapsed, cv_status::timeout otherwise.
- #7874 compile warning: thread.hpp:342: warning: type attributes are honored only at type definition.
- #7875 BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED should not be enabled by default.
- #7882 wrong exception text from condition_variable::wait(unique_lock<mutex>&).

#### Version 3.1.0 - boost 1.52

Deprecated Features:

Deprecated features since boost 1.50 available only until boost 1.55:

These deprecated features will be provided by default up to boost 1.52. If you don't want to include the deprecated features you could define BOOST_THREAD_DONT_PROVIDE_DEPRECATED_FEATURES_SINCE_V3_0_0. Since 1.53 these features will not be included any more by default. Since this version, if you want to include the deprecated features yet you could define BOOST_THREAD_PROVIDE_DEPRECATED_FEATURES_SINCE_V3_0_0. These deprecated features will be only available until boost 1.55, that is you have yet 1 year to move to the new features.

- Time related functions don't using the Boost.Chrono library, use the chrono overloads instead.

Breaking changes when BOOST_THREAD_VERSION==3 (Default value since Boost 1.53):

There are some new features which share the same interface but with different behavior. These breaking features are provided by default when BOOST_THREAD_VERSION is 3, but the user can however choose the version 2 behavior by defining the corresponding macro. As for the deprecated features, these broken features will be only available until boost 1.55.

- #6229 Rename the unique_future to future following the c++11.
- #6266 Breaking change: thread destructor should call terminate if joinable.
- #6269 Breaking change: thread move assignment should call terminate if joinable.

New Features:

- #2361 thread_specific_ptr: document nature of the key, complexity and rationale.
- #4710 C++11 compliance: Missing async().
- #7283 C++11 compliance: Add notify_all_at_thread_exit.
- #7345 C++11 compliance: Add noexcept to recursive mutex try_lock.

Fixed Bugs:

- #2797 Two problems with thread_specific_ptr.
- #5274 failed to compile future.hpp with stlport 5.1.5 under msvc8.1, because of undefined class.
- #5431 compile error in Windows CE 6.0(interlocked).
- #5696 win32 detail::set_tss_data does nothing when tss_cleanup_function is NULL.
- #6931 mutex waits forwever with Intel C++ Compiler XE 12.1.5.344 Build 20120612
- #7045 Thread library does not automatically compile date_time.
- #7173 wrong function name interrupt_point().
- #7200 Unable to build boost.thread modularized.
- #7220 gcc 4.6.2 warns about inline+dllimport functions.
- #7238 this_thread::sleep_for() does not respond to interrupt().
- #7245 Minor typos on documentation related to version 3.
- #7272 win32/thread_primitives.hpp: (Unneccessary) Warning.
- #7284 Clarify that there is no access priority between lock and shared_lock on shared mutex.
- #7329 boost/thread/future.hpp does not compile on HPUX.
- #7336 BOOST_THREAD_DONT_USE_SYSTEM doesn't work.
- #7349 packaged_task holds reference to temporary.
- #7350 allocator_destructor does not destroy object
- #7360 Memory leak in pthread implementation of boost::thread_specific_ptr
- #7370 Boost.Thread documentation
- #7438 Segmentation fault in test_once regression test in group.join_all();
- #7461 detail::win32::ReleaseSemaphore may be called with count_to_release equal to 0
- #7499 call_once doesn't call even once

#### Version 3.0.1 - boost 1.51

Deprecated Features:

Deprecated features since boost 1.50 available only until boost 1.55:

These deprecated features will be provided by default up to boost 1.52. If you don't want to include the deprecated features you could define BOOST_THREAD_DONT_PROVIDE_DEPRECATED_FEATURES_SINCE_V3_0_0. Since 1.53 these features will not be included any more by default. Since this version, if you want to include the deprecated features yet you could define BOOST_THREAD_PROVIDE_DEPRECATED_FEATURES_SINCE_V3_0_0. These deprecated features will be only available until boost 1.55, that is you have 1 year and a half to move to the new features.

- Time related functions don't using the Boost.Chrono library, use the chrono overloads instead.

Breaking changes when BOOST_THREAD_VERSION==3:

There are some new features which share the same interface but with different behavior. These breaking features are provided by default when BOOST_THREAD_VERSION is 3, but the user can however choose the version 2 behavior by defining the corresponding macro. As for the deprecated features, these broken features will be only available until boost 1.55.

- #6229 Rename the unique_future to future following the c++11.
- #6266 Breaking change: thread destructor should call terminate if joinable.
- #6269 Breaking change: thread move assignment should call terminate if joinable.

Fixed Bugs:

- #4258 Linking with boost thread does not work on mingw/gcc 4.5.
- #4885 Access violation in set_tss_data at process exit due to invalid assumption about TlsAlloc.
- #6931 mutex waits forwever with Intel Compiler and /debug:parallel
- #7044 boost 1.50.0 header missing.
- #7052 Thread: BOOST_THREAD_PROVIDES_DEPRECATED_FEATURES_SINCE_V3_0_0 only masks thread::operator==, thread::operator!= forward declarations, not definitions.
- #7066 An attempt to fix current_thread_tls_key static initialization order.
- #7074 Multiply defined symbol boost::allocator_arg.
- #7078 Trivial 64-bit warning fix on Windows for thread attribute stack size
- #7089 BOOST_THREAD_WAIT_BUG limits functionality without solving anything

#### Version 3.0.0 - boost 1.50

Breaking changes when BOOST_THREAD_VERSION==3:

- #6229 Breaking change: Rename the unique_future to future following the c++11.
- #6266 Breaking change: thread destructor should call terminate if joinable.
- #6269 Breaking change: thread move assignment should call terminate if joinable.

New Features:

- #1850 Request for unlock_guard to compliment lock_guard.
- #2637 Request for shared_mutex duration timed_lock and timed_lock_shared.
- #2741 Proposal to manage portable and non portable thread attributes.
- #3567 Request for shared_lock_guard.
- #6194 Adapt to Boost.Move.
- #6195 c++11 compliance: Provide the standard time related interface using Boost.Chrono.
- #6217 Enhance Boost.Thread shared mutex interface following Howard Hinnant proposal.
- #6224 c++11 compliance: Add the use of standard noexcept on compilers supporting them.
- #6225 Add the use of standard =delete defaulted operations on compilers supporting them.
- #6226 c++11 compliance: Add explicit bool conversion from locks.
- #6228 Add promise constructor with allocator following the standard c++11.
- #6230 c++11 compliance: Follows the exception reporting mechanism as defined in the c++11.
- #6231 Add BasicLockable requirements in the documentation to follow c++11.
- #6272 c++11 compliance: Add thread::id hash specialization.
- #6273 c++11 compliance: Add cv_status enum class and use it on the conditions wait functions.
- #6342 c++11 compliance: Adapt the one_flag to the c++11 interface.
- #6671 upgrade_lock: missing mutex and release functions.
- #6672 upgrade_lock:: missing constructors from time related types.
- #6675 upgrade_lock:: missing non-member swap.
- #6676 lock conversion should be explicit.
- Added missing packaged_task::result_type and packaged_task:: constructor with allocator.
- Added packaged_task::reset()

Fixed Bugs:

- #2380 boost::move from lvalue does not work with gcc.
- #2430 shared_mutex for win32 doesn't have timed_lock_upgrade.
- #2575 Bug- Boost 1.36.0 on Itanium platform.
- #3160 Duplicate tutorial code in boost::thread.
- #4345 thread::id and joining problem with cascade of threads.
- #4521 Error using boost::move on packaged_task (MSVC 10).
- #4711 Must use implementation details to return move-only types.
- #4921 BOOST_THREAD_USE_DLL and BOOST_THREAD_USE_LIB are crucial and need to be documented.
- #5013 documentation: boost::thread: pthreas_exit causes terminate().
- #5173 boost::this_thread::get_id is very slow.
- #5351 interrupt a future get boost::unknown_exception.
- #5516 Upgrade lock is not acquired when previous upgrade lock releases if another read lock is present.
- #5990 shared_future<T>::get() has wrong return type.
- #6174 packaged_task doesn't correctly handle moving results.
- #6222 Compile error with SunStudio: unique_future move.
- #6354 PGI: Compiler threading support is not turned on.
- #6673 shared_lock: move assign doesn't works with c++11.
- #6674 shared_mutex: try_lock_upgrade_until doesn't works.
- #6908 Compile error due to unprotected definitions of _WIN32_WINNT and WINVER.
- #6940 TIME_UTC is a macro in C11.
- #6959 call of abs is ambiguous.
- Fix issue signaled on the ML with task_object(task_object const&) in presence of task_object(task_object &&)

#### Version 2.1.1 - boost 1.49

Fixed Bugs:

- #2309 Lack of g++ symbol visibility support in Boost.Thread.
- #2639 documentation should be extended(defer_lock, try_to_lock, ...).
- #3639 Boost.Thread doesn't build with Sun-5.9 on Linux.
- #3762 Thread can't be compiled with winscw (Codewarrior by Nokia).
- #3885 document about mix usage of boost.thread and native thread api.
- #3975 Incorrect precondition for promise::set_wait_callback().
- #4048 thread::id formatting involves locale
- #4315 gcc 4.4 Warning: inline ... declared as dllimport: attribute ignored.
- #4480 OpenVMS patches for compiler issues workarounds.
- #4819 boost.thread's documentation misprints.
- #5423 thread issues with C++0x.
- #5617 boost::thread::id copy ctor.
- #5739 set-but-not-used warnings with gcc-4.6.
- #5826 threads.cpp: resource leak on threads creation failure.
- #5839 thread.cpp: ThreadProxy leaks on exceptions.
- #5859 win32 shared_mutex constructor leaks on exceptions.
- #6100 Compute hardware_concurrency() using get_nprocs() on GLIBC systems.
- #6168 recursive_mutex is using wrong config symbol (possible typo).
- #6175 Compile error with SunStudio.
- #6200 patch to have condition_variable and mutex error better handle EINTR.
- #6207 shared_lock swap compiler error on clang 3.0 c++11.
- #6208 try_lock_wrapper swap compiler error on clang 3.0 c++11.

#### Version 2.1.0 - Changes since boost 1.40

The 1.41.0 release of Boost adds futures to the thread library. There are also a few minor changes.

#### Changes since boost 1.35

The 1.36.0 release of Boost includes a few new features in the thread library:

- New generic `lock()` and `try_lock()` functions for locking multiple mutexes at once.
- Rvalue reference support for move semantics where the compilers supports it.
- A few bugs fixed and missing functions added (including the serious win32 condition variable bug).
- `scoped_try_lock` types are now backwards-compatible with Boost 1.34.0 and previous releases.
- Support for passing function arguments to the thread function by supplying additional arguments to the `boost::thread` constructor.
- Backwards-compatibility overloads added for `timed_lock` and `timed_wait` functions to allow use of `xtime` for timeouts.

#### Version 2.0.0 - Changes since boost 1.34

Almost every line of code in Boost.Thread has been changed since the 1.34 release of boost. However, most of the interface changes have been extensions, so the new code is largely backwards-compatible with the old code. The new features and breaking changes are described below.

#### New Features

- Instances of `boost::thread` and of the various lock types are now movable.
- Threads can be interrupted at interruption points.
- Condition variables can now be used with any type that implements the `Lockable` concept, through the use of `boost::condition_variable_any` (`boost::condition` is a `typedef` to `boost::condition_variable_any`, provided for backwards compatibility). `boost::condition_variable` is provided as an optimization, and will only work with `boost::unique_lock<boost::mutex>` (`boost::mutex::scoped_lock`).
- Thread IDs are separated from `boost::thread`, so a thread can obtain it's own ID (using `boost::this_thread::get_id()`), and IDs can be used as keys in associative containers, as they have the full set of comparison operators.
- Timeouts are now implemented using the Boost DateTime library, through a typedef `boost::system_time` for absolute timeouts, and with support for relative timeouts in many cases. `boost::xtime` is supported for backwards compatibility only.
- Locks are implemented as publicly accessible templates `boost::lock_guard`, `boost::unique_lock`, `boost::shared_lock`, and `boost::upgrade_lock`, which are templated on the type of the mutex. The `Lockable` concept has been extended to include publicly available `lock()` and `unlock()` member functions, which are used by the lock types.

#### Breaking Changes

The list below should cover all changes to the public interface which break backwards compatibility.

- `boost::try_mutex` has been removed, and the functionality subsumed into `boost::mutex`. `boost::try_mutex` is left as a `typedef`, but is no longer a separate class.
- `boost::recursive_try_mutex` has been removed, and the functionality subsumed into `boost::recursive_mutex`. `boost::recursive_try_mutex` is left as a `typedef`, but is no longer a separate class.
- `boost::detail::thread::lock_ops` has been removed. Code that relies on the `lock_ops` implementation detail will no longer work, as this has been removed, as it is no longer necessary now that mutex types now have public `lock()` and `unlock()` member functions.
- `scoped_lock` constructors with a second parameter of type `bool` are no longer provided. With previous boost releases,

      boost::mutex::scoped_lock some_lock(some_mutex,false);

  could be used to create a lock object that was associated with a mutex, but did not lock it on construction. This facility has now been replaced with the constructor that takes a `boost::defer_lock_type` as the second parameter:

      boost::mutex::scoped_lock some_lock(some_mutex,boost::defer_lock);

- The `locked()` member function of the `scoped_lock` types has been renamed to `owns_lock()`.
- You can no longer obtain a `boost::thread` instance representing the current thread: a default-constructed `boost::thread` object is not associated with any thread. The only use for such a thread object was to support the comparison operators: this functionality has been moved to `boost::thread::id`.
- The broken `boost::read_write_mutex` has been replaced with `boost::shared_mutex`.
- `boost::mutex` is now never recursive. For Boost releases prior to 1.35 `boost::mutex` was recursive on Windows and not on POSIX platforms.
- When using a `boost::recursive_mutex` with a call to `boost::condition_variable_any::wait()`, the mutex is only unlocked one level, and not completely. This prior behaviour was not guaranteed and did not feature in the tests.