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

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Using and building the library

Configuration
Limitations

Boost.Thread is configured following the conventions used to build libraries with separate source code. Boost.Thread will import/export the code only if the user has specifically asked for it, by defining either BOOST_ALL_DYN_LINK if they want all boost libraries to be dynamically linked, or BOOST_THREAD_DYN_LINK if they want just this one to be dynamically liked.

The definition of these macros determines whether BOOST_THREAD_USE_DLL is defined. If BOOST_THREAD_USE_DLL is not defined, the library will define BOOST_THREAD_USE_DLL or BOOST_THREAD_USE_LIB depending on whether the platform. On non windows platforms BOOST_THREAD_USE_LIB is defined if is not defined. In windows platforms, BOOST_THREAD_USE_LIB is defined if BOOST_THREAD_USE_DLL and the compiler supports auto-tss cleanup with Boost.Threads (for the time been Msvc and Intel)

The source code compiled when building the library defines a macros BOOST_THREAD_SOURCE that is used to import or export it. The user must not define this macro in any case.

Boost.Thread depends on some non header-only libraries.

It seems that there are some IDE (as e.g. Visual Studio) that deduce the libraries that a program needs to link to inspecting the sources. Such IDE could force to link to Boost.DateTime and/or Boost.Chrono.

As the single mandatory dependency is to Boost.System, the following

bjam toolset=msvc-11.0 --build-type=complete --with-thread

will install only boost_thread and boost_system.

Users of such IDE should force the Boost.Chrono and Boost.DateTime build using

bjam toolset=msvc-11.0 --build-type=complete --with-thread --with-chrono --with-date_time

The following section describes all the macros used to configure Boost.Thread.

Boost.Thread uses by default Boost.Chrono for the time related functions. For backward compatibility and also for compilers that don't work well with Boost.Chrono the user can define BOOST_THREAD_DONT_USE_CHRONO.

BOOST_THREAD_USES_CHRONO is defined when Boost.Thread uses Boost.Chrono.

Boost.Thread uses by default an internal move semantic implementation. Since version 3.0.0 you can use the move emulation emulation provided by Boost.Move.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_USES_MOVE if you want to use Boost.Move interface. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_USE_MOVE if you don't want to use Boost.Move interface.

The shared mutex implementation on Windows platform provides currently less functionality than the generic one that is used for PTheads based platforms. In order to have access to these functions, the user needs to define BOOST_THREAD_PROVIDES_GENERIC_SHARED_MUTEX_ON_WIN to use the generic implementation, that while could be less efficient, provides all the functions.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_GENERIC_SHARED_MUTEX_ON_WIN if you want these features. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_GENERIC_SHARED_MUTEX_ON_WIN if you don't want these features.

Boost.Threads includes in version 3 the Shared Locking Upwards Conversion as defined in Shared Locking. These conversions need to be used carefully to avoid deadlock or livelock. The user need to define explicitly BOOST_THREAD_PROVIDES_SHARED_MUTEX_UPWARDS_CONVERSION to get these upwards conversions.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_SHARED_MUTEX_UPWARDS_CONVERSION if you want these features. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_SHARED_MUTEX_UPWARDS_CONVERSION if you don't want these features.

In Shared Locking the lock conversions are explicit. As this explicit conversion breaks the lock interfaces, it is provided only if the BOOST_THREAD_PROVIDES_EXPLICIT_LOCK_CONVERSION is defined.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_EXPLICIT_LOCK_CONVERSION if you want these features. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_EXPLICIT_LOCK_CONVERSION if you don't want these features.

C++11 uses std::future. Versions of Boost.Thread previous to version 3.0.0 uses boost:unique_future. Since version 3.0.0 boost::future replaces boost::unique_future when BOOST_THREAD_PROVIDES_FUTURE is defined. The documentation doesn't contains anymore however boost::unique_future.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_FUTURE if you want to use boost::future. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_FUTURE if you want to use boost::unique_future.

C++11 promise initialize the associated state at construction time. Versions of Boost.Thread previous to version 3.0.0 initialize it lazily at any point in time in which this associated state is needed.

Since version 3.0.0 this difference in behavior can be configured. When BOOST_THREAD_PROVIDES_PROMISE_LAZY is defined the backward compatible behavior is provided.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_DONT_PROVIDE_PROMISE_LAZY if you want to use boost::future. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_PROVIDES_PROMISE_LAZY if you want to use boost::unique_future.

C++11 std::promise provides constructors with allocators.

template <typename R>
class promise
{
  public:
    template <class Allocator>
    explicit promise(allocator_arg_t, Allocator a);
  // ...
};
template <class R, class Alloc> struct uses_allocator<promise<R>,Alloc>: true_type {};

where

struct allocator_arg_t { };
constexpr allocator_arg_t allocator_arg = allocator_arg_t();

template <class T, class Alloc> struct uses_allocator;

Since version 3.0.0 Boost.Thread implements this constructor using the following interface

namespace boost
{
  typedef container::allocator_arg_t allocator_arg_t;
  constexpr allocator_arg_t allocator_arg = {};

  namespace container
  {
    template <class R, class Alloc>
    struct uses_allocator<promise<R>,Alloc>: true_type {};
  }
  template <class T, class Alloc>
  struct uses_allocator : public container::uses_allocator<T, Alloc> {};
}

which introduces a dependency on Boost.Container. This feature is provided only if BOOST_THREAD_PROVIDES_FUTURE_CTOR_ALLOCATORS is defined.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_FUTURE_CTOR_ALLOCATORS if you want these features. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_FUTURE_CTOR_ALLOCATORS if you don't want these features.

C++11 has a different semantic for the thread destructor and the move assignment. Instead of detaching the thread, calls to terminate() if the thread was joinable. When BOOST_THREAD_PROVIDES_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE and BOOST_THREAD_PROVIDES_THREAD_MOVE_ASSIGN_CALLS_TERMINATE_IF_JOINABLE is defined Boost.Thread provides the C++ semantic.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE if you want these features. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE if you don't want these features.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_THREAD_MOVE_ASSIGN_CALLS_TERMINATE_IF_JOINABLE if you want these features. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_THREAD_MOVE_ASSIGN_CALLS_TERMINATE_IF_JOINABLE if you don't want these features.

C++11 defines a default constructor for once_flag. When BOOST_THREAD_PROVIDES_ONCE_CXX11 is defined Boost.Thread provides this C++ semantics. In this case, the previous aggregate syntax is not supported.

boost::once_flag once = BOOST_ONCE_INIT;

You should now just do

boost::once_flag once;

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_PROVIDES_ONCE_CXX11 if you want these features. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_PROVIDE_ONCE_CXX11 if you don't want these features.

Version 3.0.0 deprecates some Boost.Thread features.

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.

BOOST_THREAD_VERSION defines the Boost.Thread version. The default version is 2. In this case the following breaking or extending macros are defined if the opposite is not requested:

  • BOOST_THREAD_PROVIDES_PROMISE_LAZY
  • BOOST_THREAD_PROVIDES_DEPRECATED_FEATURES_SINCE_V3_0_0

The user can request the version 3 by defining BOOST_THREAD_VERSION to 3. In this case the following breaking or extending macros are defined if the opposite is not requested:

  • Breaking change BOOST_THREAD_PROVIDES_EXPLICIT_LOCK_CONVERSION
  • Breaking change BOOST_THREAD_PROVIDES_FUTURE
  • Uniformity BOOST_THREAD_PROVIDES_GENERIC_SHARED_MUTEX_ON_WIN
  • Extension BOOST_THREAD_PROVIDES_SHARED_MUTEX_UPWARDS_CONVERSION
  • Conformity BOOST_THREAD_PROVIDES_FUTURE_CTOR_ALLOCATORS
  • Breaking change BOOST_THREAD_PROVIDES_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE
  • Breaking change BOOST_THREAD_PROVIDES_THREAD_MOVE_ASSIGN_CALLS_TERMINATE_IF_JOINABLE
  • Breaking change BOOST_THREAD_PROVIDES_ONCE_CXX11
  • Breaking change BOOST_THREAD_DONT_PROVIDE_PROMISE_LAZY
  • Breaking change BOOST_THREAD_DONT_PROVIDE_DEPRECATED_FEATURES_SINCE_V3_0_0

The default value for BOOST_THREAD_VERSION will be changed to 3 since Boost 1.53.

Some compilers don't work correctly with some of the added features.

If __SUNPRO_CC < 0x5100 the library defines

  • BOOST_THREAD_DONT_USE_MOVE

If __SUNPRO_CC < 0x5100 the library defines

  • BOOST_THREAD_DONT_PROVIDE_FUTURE_CTOR_ALLOCATORS

If __IBMCPP__ < 1100 the library defines

  • BOOST_THREAD_DONT_USE_CHRONO

And Boost.Thread doesn't links with Boost.Chrono.


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