Boost C++ Libraries

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Thread Management

Synopsis
Tutorial
Class thread
Namespace this_thread
Class thread_group EXTENSION

Synopsis 

#include <boost/thread/thread.hpp>

namespace boost
{
  class thread;
  void swap(thread& lhs,thread& rhs) noexcept;

  namespace this_thread
  {
    thread::id get_id() noexcept;
    template<typename TimeDuration>
    void yield() noexcept;
    template <class Clock, class Duration>
    void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
    template <class Rep, class Period>
    void sleep_for(const chrono::duration<Rep, Period>& rel_time);
    namespace no_interruption_point  // EXTENSION
    {
    	template <class Clock, class Duration>
    	void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
    	template <class Rep, class Period>
    	void sleep_for(const chrono::duration<Rep, Period>& rel_time);
    }
    template<typename Callable>
    void at_thread_exit(Callable func); // EXTENSION

    void interruption_point(); // EXTENSION
    bool interruption_requested() noexcept; // EXTENSION
    bool interruption_enabled() noexcept; // EXTENSION 
    class disable_interruption; // EXTENSION
    class restore_interruption; // EXTENSION

  #if defined BOOST_THREAD_USES_DATETIME
    template <TimeDuration>
    void sleep(TimeDuration const& rel_time);  // DEPRECATED
    void sleep(system_time const& abs_time); // DEPRECATED
  #endif
  }
  class thread_group; // EXTENSION

}

Tutorial

Launching threads
Thread attributes
Exceptions in thread functions
Detaching thread
Joining a thread
Destructor V1-2
Destructor V3-X
Interruption
Thread IDs
Using native interfaces with Boost.Thread resources
Using Boost.Thread interfaces in a native thread

The boost::thread class is responsible for launching and managing threads. Each boost::thread object represents a single thread of execution, or Not-a-Thread, and at most one boost::thread object represents a given thread of execution: objects of type boost::thread are not copyable.

Objects of type boost::thread are movable, however, so they can be stored in move-aware containers, and returned from functions. This allows the details of thread creation to be wrapped in a function. 

boost::thread make_thread();

void f()
{
    boost::thread some_thread=make_thread();
    some_thread.join();
}
[Note] Note

On compilers that support rvalue references, boost::thread provides a proper move constructor and move-assignment operator, and therefore meets the C++0x MoveConstructible and MoveAssignable concepts. With such compilers, boost::thread can therefore be used with containers that support those concepts.

For other compilers, move support is provided with a move emulation layer, so containers must explicitly detect that move emulation layer. See <boost/thread/detail/move.hpp> for details.

A new thread is launched by passing an object of a callable type that can be invoked with no parameters to the constructor. The object is then copied into internal storage, and invoked on the newly-created thread of execution. If the object must not (or cannot) be copied, then boost::ref can be used to pass in a reference to the function object. In this case, the user of Boost.Thread must ensure that the referred-to object outlives the newly-created thread of execution. 

struct callable
{
    void operator()();
};

boost::thread copies_are_safe()
{
    callable x;
    return boost::thread(x);
} // x is destroyed, but the newly-created thread has a copy, so this is OK

boost::thread oops()
{
    callable x;
    return boost::thread(boost::ref(x));
} // x is destroyed, but the newly-created thread still has a reference
  // this leads to undefined behaviour

If you wish to construct an instance of boost::thread with a function or callable object that requires arguments to be supplied, this can be done by passing additional arguments to the boost::thread constructor: 

void find_the_question(int the_answer);

boost::thread deep_thought_2(find_the_question,42);

The arguments are copied into the internal thread structure: if a reference is required, use boost::ref, just as for references to callable functions.

There is an unspecified limit on the number of additional arguments that can be passed.

Thread launched in this way are created with implementation defined thread attributes as stack size, scheduling, priority, ... or any platform specific attributes. It is not evident how to provide a portable interface that allows the user to set the platform specific attributes. Boost.Thread stay in the middle road through the class thread::attributes which allows to set at least in a portable way the stack size as follows: 

boost::thread::attributes attrs;
attrs.set_stack_size(4096*10);
boost::thread deep_thought_2(attrs, find_the_question, 42);

Even for this simple attribute there could be portable issues as some platforms could require that the stack size should have a minimal size and/or be a multiple of a given page size. The library adapts the requested size to the platform constraints so that the user doesn't need to take care of it.

This is the single attribute that is provided in a portable way. In order to set any other thread attribute at construction time the user needs to use non portable code.

On PThread platforms the user will need to get the thread attributes handle and use it for whatever attribute.

Next follows how the user could set the stack size and the scheduling policy on PThread platforms. 

boost::thread::attributes attrs;
// set portable attributes
// ...
attr.set_stack_size(4096*10);
#if defined(BOOST_THREAD_PLATFORM_WIN32)
    // ... window version
#elif defined(BOOST_THREAD_PLATFORM_PTHREAD)
    // ... pthread version
    pthread_attr_setschedpolicy(attr.native_handle(), SCHED_RR);
#else
#error "Boost threads unavailable on this platform"
#endif
boost::thread th(attrs, find_the_question, 42);

On Windows platforms it is not so simple as there is no type that compiles the thread attributes. There is a linked to the creation of a thread on Windows that is emulated via the thread::attributes class. This is the LPSECURITY_ATTRIBUTES lpThreadAttributes. Boost.Thread provides a non portable set_security function so that the user can provide it before the thread creation as follows 

#if defined(BOOST_THREAD_PLATFORM_WIN32)
  boost::thread::attributes attrs;
  // set portable attributes
  attr.set_stack_size(4096*10);
  // set non portable attribute
  LPSECURITY_ATTRIBUTES sec;
  // init sec 
  attr.set_security(sec);
  boost::thread th(attrs, find_the_question, 42);
  // Set other thread attributes using the native_handle_type.
  //...
#else
#error "Platform not supported"
#endif

If the function or callable object passed to the boost::thread constructor propagates an exception when invoked that is not of type boost::thread_interrupted, std::terminate() is called.

A thread can be detached by explicitly invoking the detach() member function on the boost::thread object. In this case, the boost::thread object ceases to represent the now-detached thread, and instead represents Not-a-Thread. 

int main()
{
  boost::thread t(my_func);
  t.detach();
}

In order to wait for a thread of execution to finish, the join(), __join_for or __join_until ( timed_join() deprecated) member functions of the boost::thread object must be used. join() will block the calling thread until the thread represented by the boost::thread object has completed. 

int main()
{
  boost::thread t(my_func);
  t.join();
}

If the thread of execution represented by the boost::thread object has already completed, or the boost::thread object represents Not-a-Thread, then join() returns immediately. 

int main()
{
  boost::thread t;
  t.join(); // do nothing
}

Timed based join are similar, except that a call to __join_for or __join_until will also return if the thread being waited for does not complete when the specified time has elapsed or reached respectively. 

int main()
{
  boost::thread t;
  if ( t.join_for(boost::chrono::milliseconds(500)) )
    // do something else
  t.join(); // join anyway
}

When the boost::thread object that represents a thread of execution is destroyed the thread becomes detached. Once a thread is detached, it will continue executing until the invocation of the function or callable object supplied on construction has completed, or the program is terminated. A thread can also be detached by explicitly invoking the detach() member function on the boost::thread object. In this case, the boost::thread object ceases to represent the now-detached thread, and instead represents Not-a-Thread.

When the boost::thread object that represents a thread of execution is destroyed the program terminates if the thread is __joinable__. 

int main()
{
  boost::thread t(my_func);
} // calls std::terminate()

You can use a thread_joiner to ensure that the thread has been joined at the thread destructor. 

int main()
{
  boost::thread t(my_func);
  boost::thread_joiner g(t);
  // do something else
} // here the thread_joiner destructor will join the thread before it is destroyed.

A running thread can be interrupted by invoking the interrupt() member function of the corresponding boost::thread object. When the interrupted thread next executes one of the specified interruption points (or if it is currently blocked whilst executing one) with interruption enabled, then a boost::thread_interrupted exception will be thrown in the interrupted thread. Unless this exception is caught inside the interrupted thread's thread-main function, the stack unwinding process (as with any other exception) causes the destructors with automatic storage duration to be executed. Unlike other exceptions, when boost::thread_interrupted is propagated out of thread-main function, this does not cause the call to std::terminate; the effect is as though the thread-main function has returned normally.

If a thread wishes to avoid being interrupted, it can create an instance of boost::this_thread::disable_interruption. Objects of this class disable interruption for the thread that created them on construction, and restore the interruption state to whatever it was before on destruction: 

void f()
{
    // interruption enabled here
    {
        boost::this_thread::disable_interruption di;
        // interruption disabled
        {
            boost::this_thread::disable_interruption di2;
            // interruption still disabled
        } // di2 destroyed, interruption state restored
        // interruption still disabled
    } // di destroyed, interruption state restored
    // interruption now enabled
}

The effects of an instance of boost::this_thread::disable_interruption can be temporarily reversed by constructing an instance of boost::this_thread::restore_interruption, passing in the boost::this_thread::disable_interruption object in question. This will restore the interruption state to what it was when the boost::this_thread::disable_interruption object was constructed, and then disable interruption again when the boost::this_thread::restore_interruption object is destroyed. 

void g()
{
    // interruption enabled here
    {
        boost::this_thread::disable_interruption di;
        // interruption disabled
        {
            boost::this_thread::restore_interruption ri(di);
            // interruption now enabled
        } // ri destroyed, interruption disable again
    } // di destroyed, interruption state restored
    // interruption now enabled
}

At any point, the interruption state for the current thread can be queried by calling boost::this_thread::interruption_enabled().

Predefined Interruption Points

The following functions are interruption points, which will throw boost::thread_interrupted if interruption is enabled for the current thread, and interruption is requested for the current thread:

Objects of class boost::thread::id can be used to identify threads. Each running thread of execution has a unique ID obtainable from the corresponding boost::thread by calling the get_id() member function, or by calling boost::this_thread::get_id() from within the thread. Objects of class boost::thread::id can be copied, and used as keys in associative containers: the full range of comparison operators is provided. Thread IDs can also be written to an output stream using the stream insertion operator, though the output format is unspecified.

Each instance of boost::thread::id either refers to some thread, or Not-a-Thread. Instances that refer to Not-a-Thread compare equal to each other, but not equal to any instances that refer to an actual thread of execution. The comparison operators on boost::thread::id yield a total order for every non-equal thread ID.

boost::thread class has members native_handle_type and native_handle providing access to the underlying native handle.

This native handle can be used to change for example the scheduling.

In general, it is not safe to use this handle with operations that can conflict with the ones provided by Boost.Thread. An example of bad usage could be detaching a thread directly as it will not change the internals of the boost::thread instance, so for example the joinable function will continue to return true, while the native thread is no more joinable. 

thread t(fct);
thread::native_handle_type hnd=t.native_handle();
pthread_detach(hnd);
assert(t.joinable());

Any thread of execution created using the native interface is called a native thread in this documentation.

The first example of a native thread of execution is the main thread.

The user can access to some synchronization functions related to the native current thread using the boost::this_thread yield, sleep, sleep_for, sleep_until, functions. 

int main() {
  // ... 
  boost::this_thread::sleep_for(boost::chrono::milliseconds(10));
  // ... 
}

Of course all the synchronization facilities provided by Boost.Thread are also available on native threads.

The boost::this_thread interrupt related functions behave in a degraded mode when called from a thread created using the native interface, i.e. boost::this_thread::interruption_enabled() returns false. As consequence the use of boost::this_thread::disable_interruption and boost::this_thread::restore_interruption will do nothing and calls to boost::this_thread::interruption_point() will be just ignored.

As the single way to interrupt a thread is through a boost::thread instance, interruption_request() will return false for the native threads.

pthread_exit POSIX limitation

pthread_exit in glibc/NPTL causes a "forced unwind" that is almost like a C++ exception, but not quite. On Mac OS X, for example, pthread_exit unwinds without calling C++ destructors.

This behavior is incompatible with the current Boost.Thread design, so the use of this function in a POSIX thread result in undefined behavior of any Boost.Thread function.

Class thread

Default Constructor
Move Constructor
Move assignment operator
Thread Constructor
Thread Attributes Constructor EXTENSION
Thread Callable Move Constructor
Thread Attributes Move Constructor EXTENSION
Thread Constructor with arguments
Thread Destructor
Member function joinable()
Member function join()
Member function timed_join() DEPRECATED
Member function try_join_for() EXTENSION
Member function try_join_until() EXTENSION
Member function detach()
Member function get_id()
Member function interrupt() EXTENSION
Static member function hardware_concurrency()
Static member function physical_concurrency()
Member function native_handle()
operator== DEPRECATED
operator!= DEPRECATED
Static member function sleep() DEPRECATED
Static member function yield() DEPRECATED
Member function swap()
Non-member function swap()
Class boost::thread::id
Class boost::thread::attributes EXTENSION
#include <boost/thread/thread.hpp>

class thread
{
public:
    class attributes; // EXTENSION

    thread() noexcept;
    ~thread();

    thread(const thread&) = delete;
    thread& operator=(const thread&) = delete;

    // move support
    thread(thread&&) noexcept;
    thread& operator=(thread&&) noexcept;

    template <class F>
    explicit thread(F f);
    template <class F>
    thread(F &&f);

    template <class F,class A1,class A2,...>
    thread(F f,A1 a1,A2 a2,...);
    template <class F, class ...Args>
    explicit thread(F&& f, Args&&... args);

    template <class F>
    explicit thread(attributes& attrs, F f); // EXTENSION
    template <class F>
    thread(attributes& attrs, F &&f); // EXTENSION
    template <class F, class ...Args>
    explicit thread(attributes& attrs, F&& f, Args&&... args);

    void swap(thread& x) noexcept;

    class id;

    id get_id() const noexcept;

    bool joinable() const noexcept;
    void join();
    template <class Rep, class Period>
    bool try_join_for(const chrono::duration<Rep, Period>& rel_time); // EXTENSION
    template <class Clock, class Duration>
    bool try_join_until(const chrono::time_point<Clock, Duration>& t); // EXTENSION

    void detach();

    static unsigned hardware_concurrency() noexcept;
    static unsigned physical_concurrency() noexcept;

    typedef platform-specific-type native_handle_type;
    native_handle_type native_handle();

    void interrupt(); // EXTENSION
    bool interruption_requested() const noexcept; // EXTENSION


#if defined BOOST_THREAD_USES_DATETIME
    bool timed_join(const system_time& wait_until); // DEPRECATED
    template<typename TimeDuration>
    bool timed_join(TimeDuration const& rel_time); // DEPRECATED
    static void sleep(const system_time& xt);// DEPRECATED
#endif

#if defined BOOST_THREAD_PROVIDES_THREAD_EQ
    bool operator==(const thread& other) const; // DEPRECATED
    bool operator!=(const thread& other) const; // DEPRECATED

#endif
    static void yield() noexcept; // DEPRECATED

};

void swap(thread& lhs,thread& rhs) noexcept;

thread() noexcept;

Effects:

Constructs a boost::thread instance that refers to Not-a-Thread.

Postconditions:

this->get_id()==thread::id()

Throws:

Nothing 

thread(thread&& other) noexcept;

Effects:

Transfers ownership of the thread managed by other (if any) to the newly constructed boost::thread instance.

Postconditions:

other.get_id()==thread::id() and get_id() returns the value of other.get_id() prior to the construction

Throws:

Nothing 

thread& operator=(thread&& other) noexcept;

Effects:

Transfers ownership of the thread managed by other (if any) to *this.

- if defined BOOST_THREAD_DONT_PROVIDE_THREAD_MOVE_ASSIGN_CALLS_TERMINATE_IF_JOINABLE: If the thread is joinable call detach(), DEPRECATED

- if defined BOOST_THREAD_PROVIDES_THREAD_MOVE_ASSIGN_CALLS_TERMINATE_IF_JOINABLE: If the thread is joinable calls to std::terminate().

Postconditions:

other->get_id()==thread::id() and get_id() returns the value of other.get_id() prior to the assignment.

Throws:

Nothing 

template<typename Callable>
thread(Callable func);

Requires:

Callable must be Copyable and func() must be a valid expression.

Effects:

func is copied into storage managed internally by the thread library, and that copy is invoked on a newly-created thread of execution. If this invocation results in an exception being propagated into the internals of the thread library that is not of type boost::thread_interrupted, then std::terminate() will be called. Any return value from this invocation is ignored.

Postconditions:

*this refers to the newly created thread of execution and this->get_id()!=thread::id().

Throws:

boost::thread_resource_error if an error occurs.

Error Conditions:

resource_unavailable_try_again : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

template<typename Callable>
thread(attributes& attrs, Callable func);

Preconditions:

Callable must be copyable.

Effects:

func is copied into storage managed internally by the thread library, and that copy is invoked on a newly-created thread of execution with the specified attributes. If this invocation results in an exception being propagated into the internals of the thread library that is not of type boost::thread_interrupted, then std::terminate() will be called. Any return value from this invocation is ignored. If the attributes declare the native thread as detached, the boost::thread will be detached.

Postconditions:

*this refers to the newly created thread of execution and this->get_id()!=thread::id().

Throws:

boost::thread_resource_error if an error occurs.

Error Conditions:

resource_unavailable_try_again : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

template<typename Callable>
thread(Callable &&func);

Preconditions:

Callable must be Movable.

Effects:

func is moved into storage managed internally by the thread library, and that copy is invoked on a newly-created thread of execution. If this invocation results in an exception being propagated into the internals of the thread library that is not of type boost::thread_interrupted, then std::terminate() will be called. Any return value from this invocation is ignored.

Postconditions:

*this refers to the newly created thread of execution and this->get_id()!=thread::id().

Throws:

boost::thread_resource_error if an error occurs.

Error Conditions:

resource_unavailable_try_again : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

template<typename Callable>
thread(attributes& attrs, Callable func);

Preconditions:

Callable must be copyable.

Effects:

func is copied into storage managed internally by the thread library, and that copy is invoked on a newly-created thread of execution with the specified attributes. If this invocation results in an exception being propagated into the internals of the thread library that is not of type boost::thread_interrupted, then std::terminate() will be called. Any return value from this invocation is ignored. If the attributes declare the native thread as detached, the boost::thread will be detached.

Postconditions:

*this refers to the newly created thread of execution and this->get_id()!=thread::id().

Throws:

boost::thread_resource_error if an error occurs.

Error Conditions:

resource_unavailable_try_again : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

template <class F,class A1,class A2,...>
thread(F f,A1 a1,A2 a2,...);

Preconditions:

F and each An must be copyable or movable.

Effects:

As if thread(boost::bind(f,a1,a2,...)). Consequently, f and each an are copied into internal storage for access by the new thread.

Postconditions:

*this refers to the newly created thread of execution.

Throws:

boost::thread_resource_error if an error occurs.

Error Conditions:

resource_unavailable_try_again : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded.

Note:

Currently up to nine additional arguments a1 to a9 can be specified in addition to the function f. 

~thread();

Effects:

- if defined BOOST_THREAD_DONT_PROVIDE_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE: If the thread is joinable calls detach(), DEPRECATED

- if defined BOOST_THREAD_PROVIDES_THREAD_DESTRUCTOR_CALLS_TERMINATE_IF_JOINABLE: If the thread is joinable calls to std::terminate. Destroys *this.

Throws:

Nothing.

Note:

The reason to moving to std::terminate is that either implicitly detaching or joining a joinable() thread in its destructor could result in difficult to debug correctness (for detach) or performance (for join) bugs encountered only when an exception is raised. Thus the programmer must ensure that the destructor is never executed while the thread is still joinable. Join the thread before destroying or use a scoped thread. 

bool joinable() const noexcept;

Returns:

true if *this refers to a thread of execution, false otherwise.

Throws:

Nothing 

void join();

Preconditions:

the thread is joinable.

Effects:

If *this refers to a thread of execution, waits for that thread of execution to complete.

Synchronization:

The completion of the thread represented by *this synchronizes with the corresponding successful join() return.

Note:

Operations on *this are not synchronized.

Postconditions:

If *this refers to a thread of execution on entry, that thread of execution has completed. *this no longer refers to any thread of execution.

Throws:

boost::thread_interrupted if the current thread of execution is interrupted or system_error

Error Conditions:

resource_deadlock_would_occur: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

invalid_argument: if the thread is not joinable and BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED is defined.

Notes:

join() is one of the predefined interruption points. 

bool timed_join(const system_time& wait_until);

template<typename TimeDuration>
bool timed_join(TimeDuration const& rel_time);
[Warning] Warning

DEPRECATED since 3.00.

Use instead try_join_for, try_join_until.

Preconditions:

the thread is joinable.

Effects:

If *this refers to a thread of execution, waits for that thread of execution to complete, the time wait_until has been reach or the specified duration rel_time has elapsed. If *this doesn't refer to a thread of execution, returns immediately.

Returns:

true if *this refers to a thread of execution on entry, and that thread of execution has completed before the call times out, false otherwise.

Postconditions:

If *this refers to a thread of execution on entry, and timed_join returns true, that thread of execution has completed, and *this no longer refers to any thread of execution. If this call to timed_join returns false, *this is unchanged.

Throws:

boost::thread_interrupted if the current thread of execution is interrupted or system_error

Error Conditions:

resource_deadlock_would_occur: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

invalid_argument: if the thread is not joinable and BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED is defined.

Notes:

timed_join() is one of the predefined interruption points. 

template <class Rep, class Period>
bool try_join_for(const chrono::duration<Rep, Period>& rel_time);

Preconditions:

the thread is joinable.

Effects:

If *this refers to a thread of execution, waits for that thread of execution to complete, the specified duration rel_time has elapsed. If *this doesn't refer to a thread of execution, returns immediately.

Returns:

true if *this refers to a thread of execution on entry, and that thread of execution has completed before the call times out, false otherwise.

Postconditions:

If *this refers to a thread of execution on entry, and try_join_for returns true, that thread of execution has completed, and *this no longer refers to any thread of execution. If this call to try_join_for returns false, *this is unchanged.

Throws:

boost::thread_interrupted if the current thread of execution is interrupted or system_error

Error Conditions:

resource_deadlock_would_occur: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

invalid_argument: if the thread is not joinable and BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED is defined.

Notes:

try_join_for() is one of the predefined interruption points. 

template <class Clock, class Duration>
bool try_join_until(const chrono::time_point<Clock, Duration>& abs_time);

Preconditions:

the thread is joinable.

Effects:

If *this refers to a thread of execution, waits for that thread of execution to complete, the time abs_time has been reach. If *this doesn't refer to a thread of execution, returns immediately.

Returns:

true if *this refers to a thread of execution on entry, and that thread of execution has completed before the call times out, false otherwise.

Postconditions:

If *this refers to a thread of execution on entry, and try_join_until returns true, that thread of execution has completed, and *this no longer refers to any thread of execution. If this call to try_join_until returns false, *this is unchanged.

Throws:

boost::thread_interrupted if the current thread of execution is interrupted or system_error

Error Conditions:

resource_deadlock_would_occur: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

invalid_argument: if the thread is not joinable and BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED is defined.

Notes:

try_join_until() is one of the predefined interruption points. 

void detach();

Preconditions:

the thread is joinable.

Effects:

The thread of execution becomes detached, and no longer has an associated boost::thread object.

Postconditions:

*this no longer refers to any thread of execution.

Throws:

system_error

Error Conditions:

no_such_process: if the thread is not valid.

invalid_argument: if the thread is not joinable and BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED is defined. 

thread::id get_id() const noexcept;

Returns:

If *this refers to a thread of execution, an instance of boost::thread::id that represents that thread. Otherwise returns a default-constructed boost::thread::id.

Throws:

Nothing 

void interrupt();

Effects:

If *this refers to a thread of execution, request that the thread will be interrupted the next time it enters one of the predefined interruption points with interruption enabled, or if it is currently blocked in a call to one of the predefined interruption points with interruption enabled. Otherwise do noting.

Throws:

Nothing 

unsigned hardware_concurrency() noexcept;

Returns:

The number of hardware threads available on the current system (e.g. number of CPUs or cores or hyperthreading units), or 0 if this information is not available.

Throws:

Nothing 

unsigned physical_concurrency() noexcept;

Returns:

The number of physical cores available on the current system. In contrast to hardware_concurrency() it does not return the number of virtual cores, but it counts only physical cores.

Throws:

Nothing 

typedef platform-specific-type native_handle_type;
native_handle_type native_handle();

Effects:

Returns an instance of native_handle_type that can be used with platform-specific APIs to manipulate the underlying implementation. If no such instance exists, native_handle() and native_handle_type are not present.

Throws:

Nothing. 

bool operator==(const thread& other) const;
[Warning] Warning

DEPRECATED since 4.0.0.

Use a.get_id()==b.get_id() instead`.

Returns:

get_id()==other.get_id() 

bool operator!=(const thread& other) const;
[Warning] Warning

DEPRECATED since 4.0.0.

Use a.get_id()!=b.get_id() instead`.

Returns:

get_id()!=other.get_id() 

void sleep(system_time const& abs_time);
[Warning] Warning

DEPRECATED since 3.0.0.

Use this_thread::sleep_for() or this_thread::sleep_until().

Effects:

Suspends the current thread until the specified time has been reached.

Throws:

boost::thread_interrupted if the current thread of execution is interrupted.

Notes:

sleep() is one of the predefined interruption points. 

void yield();
[Warning] Warning

DEPRECATED since 3.0.0.

Use this_thread::yield().

Effects:

See boost::this_thread::yield(). 

void swap(thread& other) noexcept;

Effects:

Exchanges the threads of execution associated with *this and other, so *this is associated with the thread of execution associated with other prior to the call, and vice-versa.

Postconditions:

this->get_id() returns the same value as other.get_id() prior to the call. other.get_id() returns the same value as this->get_id() prior to the call.

Throws:

Nothing. 

#include <boost/thread/thread.hpp>

void swap(thread& lhs,thread& rhs) noexcept;

Effects:

lhs.swap(rhs).

Default constructor
operator==
operator!=
operator<
operator>
operator<=
operator>=
Friend operator<<
#include <boost/thread/thread.hpp>

class thread::id
{
public:
    id() noexcept;

    bool operator==(const id& y) const noexcept;
    bool operator!=(const id& y) const noexcept;
    bool operator<(const id& y) const noexcept;
    bool operator>(const id& y) const noexcept;
    bool operator<=(const id& y) const noexcept;
    bool operator>=(const id& y) const noexcept;

    template<class charT, class traits>
    friend std::basic_ostream<charT, traits>&
    operator<<(std::basic_ostream<charT, traits>& os, const id& x);
};

id() noexcept;

Effects:

Constructs a boost::thread::id instance that represents Not-a-Thread.

Throws:

Nothing 

bool operator==(const id& y) const noexcept;

Returns:

true if *this and y both represent the same thread of execution, or both represent Not-a-Thread, false otherwise.

Throws:

Nothing 

bool operator!=(const id& y) const noexcept;

Returns:

true if *this and y represent different threads of execution, or one represents a thread of execution, and the other represent Not-a-Thread, false otherwise.

Throws:

Nothing 

bool operator<(const id& y) const noexcept;

Returns:

true if *this!=y is true and the implementation-defined total order of boost::thread::id values places *this before y, false otherwise.

Throws:

Nothing

Note:

A boost::thread::id instance representing Not-a-Thread will always compare less than an instance representing a thread of execution. 

bool operator>(const id& y) const noexcept;

Returns:

y<*this

Throws:

Nothing 

bool operator<=(const id& y) const noexcept;

Returns:

!(y<*this)

Throws:

Nothing 

bool operator>=(const id& y) const noexcept;

Returns:

!(*this<y)

Throws:

Nothing 

template<class charT, class traits>
friend std::basic_ostream<charT, traits>&
operator<<(std::basic_ostream<charT, traits>& os, const id& x);

Effects:

Writes a representation of the boost::thread::id instance x to the stream os, such that the representation of two instances of boost::thread::id a and b is the same if a==b, and different if a!=b.

Returns:

os

Default constructor
Member function set_stack_size()
Member function get_stack_size()
Member function native_handle()
class thread::attributes {
public:
    attributes() noexcept;
    ~ attributes()=default;
    // stack
    void set_stack_size(std::size_t size) noexcept;
    std::size_t get_stack_size() const noexcept;

#if defined BOOST_THREAD_DEFINES_THREAD_ATTRIBUTES_NATIVE_HANDLE
    typedef platform-specific-type native_handle_type;
    native_handle_type* native_handle() noexcept;
    const native_handle_type* native_handle() const noexcept;
#endif

};

thread_attributes() noexcept;

Effects:

Constructs a thread attributes instance with its default values.

Throws:

Nothing 

void set_stack_size(std::size_t size) noexcept;

Effects:

Stores the stack size to be used to create a thread. This is a hint that the implementation can choose a better size if to small or too big or not aligned to a page.

Postconditions:

this-> get_stack_size() returns the chosen stack size.

Throws:

Nothing. 

std::size_t get_stack_size() const noexcept;

Returns:

The stack size to be used on the creation of a thread. Note that this function can return 0 meaning the default.

Throws:

Nothing. 

typedef platform-specific-type native_handle_type;
    typedef platform-specific-type native_handle_type;
    native_handle_type* native_handle() noexcept;
    const native_handle_type* native_handle() const noexcept;

Effects:

Returns an instance of native_handle_type that can be used with platform-specific APIs to manipulate the underlying thread attributes implementation. If no such instance exists, native_handle() and native_handle_type are not present and BOOST_THREAD_DEFINES_THREAD_ATTRIBUTES_NATIVE_HANDLE is not defined.

Throws:

Nothing.

Namespace this_thread

Non-member function get_id()
Non-member function interruption_point() EXTENSION
Non-member function interruption_requested() EXTENSION
Non-member function interruption_enabled() EXTENSION
Non-member function sleep() DEPRECATED
Non-member function sleep_until()
Non-member function sleep_for()
Non-member function yield()
Class disable_interruption EXTENSION
Class restore_interruption EXTENSION
Non-member function template at_thread_exit() EXTENSION
namespace boost {
  namespace this_thread {
    thread::id get_id() noexcept;
    template<typename TimeDuration>
    void yield() noexcept;
    template <class Clock, class Duration>
    void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
    template <class Rep, class Period>
    void sleep_for(const chrono::duration<Rep, Period>& rel_time);

    template<typename Callable>
    void at_thread_exit(Callable func); // EXTENSION

    void interruption_point(); // EXTENSION
    bool interruption_requested() noexcept; // EXTENSION
    bool interruption_enabled() noexcept; // EXTENSION
    class disable_interruption; // EXTENSION
    class restore_interruption; // EXTENSION

  #if defined BOOST_THREAD_USES_DATETIME
    void sleep(TimeDuration const& rel_time); // DEPRECATED
    void sleep(system_time const& abs_time);  // DEPRECATED
  #endif
  }
}

#include <boost/thread/thread.hpp>

namespace this_thread
{
    thread::id get_id() noexcept;
}

Returns:

An instance of boost::thread::id that represents that currently executing thread.

Throws:

boost::thread_resource_error if an error occurs. 

#include <boost/thread/thread.hpp>

namespace this_thread
{
    void interruption_point();
}

Effects:

Check to see if the current thread has been interrupted.

Throws:

boost::thread_interrupted if boost::this_thread::interruption_enabled() and boost::this_thread::interruption_requested() both return true. 

#include <boost/thread/thread.hpp>

namespace this_thread
{
    bool interruption_requested() noexcept;
}

Returns:

true if interruption has been requested for the current thread, false otherwise.

Throws:

Nothing. 

#include <boost/thread/thread.hpp>

namespace this_thread
{
    bool interruption_enabled() noexcept;
}

Returns:

true if interruption has been enabled for the current thread, false otherwise.

Throws:

Nothing. 

#include <boost/thread/thread.hpp>

namespace this_thread
{
    template<typename TimeDuration>
    void sleep(TimeDuration const& rel_time);
    void sleep(system_time const& abs_time)
}
[Warning] Warning

DEPRECATED since 3.0.0.

Use sleep_for() and sleep_until() instead.

Effects:

Suspends the current thread until the time period specified by rel_time has elapsed or the time point specified by abs_time has been reached.

Throws:

boost::thread_interrupted if the current thread of execution is interrupted.

Notes:

sleep() is one of the predefined interruption points. 

#include <boost/thread/thread.hpp>

namespace this_thread
{
  template <class Clock, class Duration>
  void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
  namespace no_interruption_point
  {
    template <class Clock, class Duration>
    void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
  }
}

Effects:

Suspends the current thread until the time point specified by abs_time has been reached.

Throws:

Nothing if Clock satisfies the TrivialClock requirements and operations of Duration do not throw exceptions. boost::thread_interrupted if the current thread of execution is interrupted.

Notes:

sleep_until() is one of the predefined interruption points.

Notes:

no_interruption_point::sleep_until() is NOT one of the interruption points. 

#include <boost/thread/thread.hpp>

namespace this_thread
{
  template <class Rep, class Period>
  void sleep_for(const chrono::duration<Rep, Period>& rel_time);
  namespace no_interruption_point
  {
    template <class Rep, class Period>
    void sleep_for(const chrono::duration<Rep, Period>& rel_time);
  }
}

Effects:

Suspends the current thread until the duration specified by rel_time has elapsed.

Throws:

Nothing if operations of chrono::duration<Rep, Period> do not throw exceptions. boost::thread_interrupted if the current thread of execution is interrupted.

Notes:

sleep_for() is one of the predefined interruption points.

Notes:

no_interruption_point:: sleep_for() is NOT one of the interruption points. 

#include <boost/thread/thread.hpp>

namespace this_thread
{
    void yield() noexcept;
}

Effects:

Gives up the remainder of the current thread's time slice, to allow other threads to run.

Throws:

Nothing.

Constructor
Destructor
#include <boost/thread/thread.hpp>

namespace this_thread
{
    class disable_interruption
    {
    public:
        disable_interruption(const disable_interruption&) = delete;
        disable_interruption& operator=(const disable_interruption&) = delete;
        disable_interruption() noexcept;
        ~disable_interruption() noexcept;
    };
}

boost::this_thread::disable_interruption disables interruption for the current thread on construction, and restores the prior interruption state on destruction. Instances of disable_interruption cannot be copied or moved. 

disable_interruption() noexcept;

Effects:

Stores the current state of boost::this_thread::interruption_enabled() and disables interruption for the current thread.

Postconditions:

boost::this_thread::interruption_enabled() returns false for the current thread.

Throws:

Nothing. 

~disable_interruption() noexcept;

Preconditions:

Must be called from the same thread from which *this was constructed.

Effects:

Restores the current state of boost::this_thread::interruption_enabled() for the current thread to that prior to the construction of *this.

Postconditions:

boost::this_thread::interruption_enabled() for the current thread returns the value stored in the constructor of *this.

Throws:

Nothing.

Constructor
Destructor
#include <boost/thread/thread.hpp>

namespace this_thread
{
    class restore_interruption
    {
    public:
        restore_interruption(const restore_interruption&) = delete;
        restore_interruption& operator=(const restore_interruption&) = delete;
        explicit restore_interruption(disable_interruption& disabler) noexcept;
        ~restore_interruption() noexcept;
    };
}

On construction of an instance of boost::this_thread::restore_interruption, the interruption state for the current thread is restored to the interruption state stored by the constructor of the supplied instance of boost::this_thread::disable_interruption. When the instance is destroyed, interruption is again disabled. Instances of restore_interruption cannot be copied or moved. 

explicit restore_interruption(disable_interruption& disabler) noexcept;

Preconditions:

Must be called from the same thread from which disabler was constructed.

Effects:

Restores the current state of boost::this_thread::interruption_enabled() for the current thread to that prior to the construction of disabler.

Postconditions:

boost::this_thread::interruption_enabled() for the current thread returns the value stored in the constructor of disabler.

Throws:

Nothing. 

~restore_interruption() noexcept;

Preconditions:

Must be called from the same thread from which *this was constructed.

Effects:

Disables interruption for the current thread.

Postconditions:

boost::this_thread::interruption_enabled() for the current thread returns false.

Throws:

Nothing. 

#include <boost/thread/thread.hpp>

template<typename Callable>
void at_thread_exit(Callable func);

Effects:

A copy of func is placed in thread-specific storage. This copy is invoked when the current thread exits (even if the thread has been interrupted).

Postconditions:

A copy of func has been saved for invocation on thread exit.

Throws:

std::bad_alloc if memory cannot be allocated for the copy of the function, boost::thread_resource_error if any other error occurs within the thread library. Any exception thrown whilst copying func into internal storage.

Note:

This function is not called if the thread was terminated forcefully using platform-specific APIs, or if the thread is terminated due to a call to exit(), abort() or std::terminate(). In particular, returning from main() is equivalent to call to exit(), so will not call any functions registered with at_thread_exit()

Class thread_group EXTENSION

Constructor
Destructor
Member function create_thread()
Member function add_thread()
Member function remove_thread()
Member function join_all()
Member function is_this_thread_in()
Member function is_thread_in()
Member function interrupt_all()
Member function size()
#include <boost/thread/thread.hpp>

class thread_group
{
public:
    thread_group(const thread_group&) = delete;
    thread_group& operator=(const thread_group&) = delete;

    thread_group();
    ~thread_group();

    template<typename F>
    thread* create_thread(F threadfunc);
    void add_thread(thread* thrd);
    void remove_thread(thread* thrd);
    bool is_this_thread_in();
    bool is_thread_in(thread* thrd);
    void join_all();
    void interrupt_all();
    int size() const;
};

thread_group provides for a collection of threads that are related in some fashion. New threads can be added to the group with add_thread and create_thread member functions. thread_group is not copyable or movable. 

thread_group();

Effects:

Create a new thread group with no threads. 

~thread_group();

Effects:

Destroy *this and delete all boost::thread objects in the group. 

template<typename F>
thread* create_thread(F threadfunc);

Effects:

Create a new boost::thread object as-if by new thread(threadfunc) and add it to the group.

Postcondition:

this->size() is increased by one, the new thread is running.

Returns:

A pointer to the new boost::thread object. 

void add_thread(thread* thrd);

Precondition:

The expression delete thrd is well-formed and will not result in undefined behaviour and is_thread_in(thrd) == false.

Effects:

Take ownership of the boost::thread object pointed to by thrd and add it to the group.

Postcondition:

this->size() is increased by one. 

void remove_thread(thread* thrd);

Effects:

If thrd is a member of the group, remove it without calling delete.

Postcondition:

If thrd was a member of the group, this->size() is decreased by one. 

void join_all();

Requires:

is_this_thread_in() == false.

Effects:

Call join() on each boost::thread object in the group.

Postcondition:

Every thread in the group has terminated.

Note:

Since join() is one of the predefined interruption points, join_all() is also an interruption point. 

bool is_this_thread_in();

Returns:

true if there is a thread th in the group such that th.get_id() == this_thread::get_id(). 

bool is_thread_in(thread* thrd);

Returns:

true if there is a thread th in the group such that th.get_id() == thrd->get_id(). 

void interrupt_all();

Effects:

Call interrupt() on each boost::thread object in the group. 

int size();

Returns:

The number of threads in the group.

Throws:

Nothing.

Copyright © 2007 -11 Anthony Williams
Copyright © 2011 -17 Vicente J. Botet Escriba

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

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