This makes it possible to use std::thread without including the whole of
<thread>. It also makes this_thread::get_id() and this_thread::yield()
available even when there is no gthreads support (e.g. when GCC is built
with --disable-threads or --enable-threads=single).
In order for the std:🧵:id return type of this_thread::get_id() to
be defined, std:thread itself is defined unconditionally. However the
constructor that creates new threads is not defined for single-threaded
builds. The thread::join() and thread::detach() member functions are
defined inline for single-threaded builds and just throw an exception
(because we know the thread cannot be joinable if the constructor that
creates joinable threads doesn't exit).
The thread::hardware_concurrency() member function is also defined
inline and returns 0 (as suggested by the standard when the value "is
not computable or well-defined").
The main benefit for most targets is that other headers such as <future>
do not need to include the whole of <thread> just to be able to create a
std::thread. That avoids including <stop_token> and std::jthread where
not required. This is another partial fix for PR 92546.
This also means we can use this_thread::get_id() and this_thread::yield()
in <stop_token> instead of using the gthread functions directly. This
removes some preprocessor conditionals, simplifying the code.
libstdc++-v3/ChangeLog:
PR libstdc++/92546
* include/Makefile.am: Add new <bits/std_thread.h> header.
* include/Makefile.in: Regenerate.
* include/std/future: Include new header instead of <thread>.
* include/std/stop_token: Include new header instead of
<bits/gthr.h>.
(stop_token::_S_yield()): Use this_thread::yield().
(_Stop_state_t::_M_requester): Change type to std:🧵:id.
(_Stop_state_t::_M_request_stop()): Use this_thread::get_id().
(_Stop_state_t::_M_remove_callback(_Stop_cb*)): Likewise.
Use __is_single_threaded() to decide whether to synchronize.
* include/std/thread (thread, operator==, this_thread::get_id)
(this_thread::yield): Move to new header.
(operator<=>, operator!=, operator<, operator<=, operator>)
(operator>=, hash<thread::id>, operator<<): Define even when
gthreads not available.
* src/c++11/thread.cc: Include <memory>.
* include/bits/std_thread.h: New file.
(thread, operator==, this_thread::get_id, this_thread::yield):
Define even when gthreads not available.
[!_GLIBCXX_HAS_GTHREADS] (thread::join, thread::detach)
(thread::hardware_concurrency): Define inline.
To poll a std::future to see if it's ready you have to call one of the
timed waiting functions. The most obvious way is wait_for(0s) but this
was previously very inefficient because it would turn the relative
timeout to an absolute one by calling system_clock::now(). When the
relative timeout is zero (or less) we're obviously going to get a time
that has already passed, but the overhead of obtaining the current time
can be dozens of microseconds. The alternative is to call wait_until
with an absolute timeout that is in the past. If you know the clock's
epoch is in the past you can use a default constructed time_point.
Alternatively, using some_clock::time_point::min() gives the earliest
time point supported by the clock, which should be safe to assume is in
the past. However, using a futex wait with an absolute timeout before
the UNIX epoch fails and sets errno=EINVAL. The new code using futex
waits with absolute timeouts was not checking for this case, which could
result in hangs (or killing the process if the libray is built with
assertions enabled).
This patch checks for times before the epoch before attempting to wait
on a futex with an absolute timeout, which fixes the hangs or crashes.
It also makes it very fast to poll using an absolute timeout before the
epoch (because we skip the futex syscall).
It also makes future::wait_for avoid waiting at all when the relative
timeout is zero or less, to avoid the unnecessary overhead of getting
the current time. This makes polling with wait_for(0s) take only a few
cycles instead of dozens of milliseconds.
libstdc++-v3/ChangeLog:
* include/std/future (future::wait_for): Do not wait for
durations less than or equal to zero.
* src/c++11/futex.cc (_M_futex_wait_until)
(_M_futex_wait_until_steady): Do not wait for timeouts before
the epoch.
* testsuite/30_threads/future/members/poll.cc: New test.
This fixes some multiple definition errors caused by the changes for
PR libstdc++/90295. The previous solution for inlining the members of
std::exception_ptr but still exporting them from the library was to
suppress the 'inline' keyword on those functions when compiling
libsupc++/eh_ptr.cc, so they get defined in that file. That produces ODR
violations though, because there are now both inline and non-inline
definitions in the library, due to the use of std::exception_ptr in
other files sucg as src/c++11/future.cc.
The new solution is to define all the relevant members as 'inline'
unconditionally, but use __attribute__((used)) to cause definitions to
be emitted in libsupc++/eh_ptr.cc as before. This doesn't quite work
however, because PR c++/67453 means the attribute is ignored on
constructors and destructors. As a workaround, the old solution
(conditionally inline) is still used for those members, but they are
given the always_inline attribute so that they aren't emitted in
src/c++11/future.o as inline definitions.
libstdc++-v3/ChangeLog:
PR libstdc++/97729
* include/std/future (__basic_future::_M_get_result): Use
nullptr for null pointer constant.
* libsupc++/eh_ptr.cc (operator==, operator!=): Remove
definitions.
* libsupc++/exception_ptr.h (_GLIBCXX_EH_PTR_USED): Define
macro to conditionally add __attribute__((__used__)).
(operator==, operator!=, exception_ptr::exception_ptr())
(exception_ptr::exception_ptr(const exception_ptr&))
(exception_ptr::~exception_ptr())
(exception_ptr::operator=(const exception_ptr&))
(exception_ptr::swap(exception_ptr&)): Always define as
inline. Add macro to be conditionally "used".
By moving std::make_obj_using_allocator and the related "utility
functions for uses-allocator construction" to a new header, we can avoid
including the whole of <memory> in <scoped_allocator> and
<memory_resource>.
In order to simplify the implementation of those utility functions they
now use concepts unconditionally. They are no longer defined if
__cpp_concepts is not defined. To simplify the code that uses those
functions I've introduced a __cpp_lib_make_obj_using_allocator feature
test macro (not specified in the standard, which might be an oversight).
That allows the code in <memory_resource> and <scoped_allocator> to
check the feature test macro to decide whether to use the new utilities,
or fall back to the C++17 code.
At the same time, this reshuffles some of the headers included by
<memory> so that they are (mostly?) self-contained. It should no longer
be necessary to include other headers before <bits/shared_ptr.h> when
other parts of the library want to use std::shared_ptr without including
the whole of <memory>.
libstdc++-v3/ChangeLog:
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/bits/shared_ptr.h: Include <iosfwd>.
* include/bits/shared_ptr_base.h: Include required headers here
directly, instead of in <memory>.
* include/bits/uses_allocator_args.h: New file. Move utility
functions for uses-allocator construction from <memory> to here.
Only define the utility functions when concepts are available.
(__cpp_lib_make_obj_using_allocator): Define non-standard
feature test macro.
* include/std/condition_variable: Remove unused headers.
* include/std/future: Likewise.
* include/std/memory: Remove headers that are not needed
directly, and are now inclkuded where they're needed. Include
new <bits/uses_allocator_args.h> header.
* include/std/memory_resource: Include only the necessary
headers. Use new feature test macro to detect support for the
utility functions.
* include/std/scoped_allocator: Likewise.
* include/std/version (__cpp_lib_make_obj_using_allocator):
Define.
Add a static_assertions to check the result type is destructible, as in
the proposed resolution for LWG 3466 (which supersedes 3458).
libstdc++-v3/ChangeLog:
* include/std/future (future, shared_future. promise): Add
is_destructible assertion (LWG 3466). Adjust string-literal for
!is_array and !is_function assertions.
* testsuite/30_threads/future/requirements/lwg3458.cc: Check
types with no accessible destructor. Adjust expected errors.
* testsuite/30_threads/promise/requirements/lwg3466.cc:
Likewise.
* testsuite/30_threads/shared_future/requirements/lwg3458.cc:
Likewise.
As was previously done for std::thread, this removes an unnecessary copy
of an rvalue of type thread::_Invoker. Instead of creating the rvalue
and then moving that into the shared state, the member of the shared
state is initialized directly from the forwarded callable and bound
arguments.
This also slightly simplifies std::thread creation to remove the
_S_make_state helper function.
libstdc++-v3/ChangeLog:
PR libstdc++/69724
* include/std/future (__future_base::_S_make_deferred_state)
(__future_base::_S_make_async_state): Remove.
(__future_base::_Deferred_state): Change constructor to accept a
parameter pack of arguments and forward them to the call
wrapper.
(__future_base::_Async_state_impl): Likewise. Replace lambda
expression with a named member function.
(async): Construct state object directly from the arguments,
instead of using thread::__make_invoker, _S_make_deferred_state
and _S_make_async_state. Move shared state into the returned
future.
* include/std/thread (thread::_Call_wrapper): New alias
template for use by constructor and std::async.
(thread::thread(Callable&&, Args&&...)): Create state object
directly instead of using _S_make_state.
(thread::__make_invoker, thread::__decayed_tuple)
(thread::_S_make_state): Remove.
* testsuite/30_threads/async/69724.cc: New test.
LWG recently decided it should be ill-formed to instantiate std::future
and std::shared_future for types that can't be returned from a function.
This adds static assertions to enforce it (std::future already failed,
but this makes the error more understandable).
LWG 3466 extends that to std::promise. The actual constraint is that
t.~T() is well-formed for the primary template, but rejecting arrays and
functions as done for futures matches that condition.
libstdc++-v3/ChangeLog:
* include/std/future (future, shared_future, promise): Add
static assertions to the primary template to reject array and
function types.
* testsuite/30_threads/future/requirements/lwg3458.cc: New test.
* testsuite/30_threads/promise/requirements/lwg3466.cc: New test.
* testsuite/30_threads/shared_future/requirements/lwg3458.cc: New test.
For C++20 the wait_until members of mutexes and condition variables are
required to be ill-formed if given a clock that doesn't meet the
requirements for a clock type. To implement that requirement this patch
adds static assertions using the chrono::is_clock trait, and defines
that trait.
To avoid expensive checks for the common cases, the trait (and
associated variable template) are explicitly specialized for the
standard clock types.
This also moves the filesystem::__file_clock type from <filesystem> to
<chrono>, so that chrono::file_clock and chrono::file_time can be
defined in <chrono> as required.
* include/bits/fs_fwd.h (filesystem::__file_clock): Move to ...
* include/std/chrono (filesystem::__file_clock): Here.
(filesystem::__file_clock::from_sys, filesystem::__file_clock::to_sys):
Define public member functions for C++20.
(is_clock, is_clock_v): Define traits for C++20.
* include/std/condition_variable (condition_variable::wait_until): Add
check for valid clock.
* include/std/future (_State_baseV2::wait_until): Likewise.
* include/std/mutex (__timed_mutex_impl::_M_try_lock_until): Likewise.
* include/std/shared_mutex (shared_timed_mutex::try_lock_shared_until):
Likewise.
* include/std/thread (this_thread::sleep_until): Likewise.
* testsuite/30_threads/condition_variable/members/2.cc: Qualify
slow_clock with new namespace.
* testsuite/30_threads/condition_variable/members/clock_neg.cc: New
test.
* testsuite/30_threads/condition_variable_any/members/clock_neg.cc:
New test.
* testsuite/30_threads/future/members/clock_neg.cc: New test.
* testsuite/30_threads/recursive_timed_mutex/try_lock_until/3.cc:
Qualify slow_clock with new namespace.
* testsuite/30_threads/recursive_timed_mutex/try_lock_until/
clock_neg.cc: New test.
* testsuite/30_threads/shared_future/members/clock_neg.cc: New
test.
* testsuite/30_threads/shared_lock/locking/clock_neg.cc: New test.
* testsuite/30_threads/shared_timed_mutex/try_lock_until/clock_neg.cc:
New test.
* testsuite/30_threads/timed_mutex/try_lock_until/3.cc: Qualify
slow_clock with new namespace.
* testsuite/30_threads/timed_mutex/try_lock_until/4.cc: Likewise.
* testsuite/30_threads/timed_mutex/try_lock_until/clock_neg.cc: New
test.
* testsuite/30_threads/unique_lock/locking/clock_neg.cc: New test.
* testsuite/std/time/traits/is_clock.cc: New test.
* testsuite/util/slow_clock.h (slow_clock): Move to __gnu_test
namespace.
* doc/xml/manual/evolution.xml: Document LWG DR 2921 change.
* doc/xml/manual/intro.xml: Likewise.
* include/std/future (__create_task_state): Add default arguments
to make providing an allocator optional.
(packaged_task::packaged_task(F&&)): Call __create_task_state directly
instead of delegating to another constructor.
(packaged_task::packaged_task(allocator_arg_t, const A&, ...)): Do not
define allocator-extended constructors for C++17 and later.
* testsuite/30_threads/packaged_task/cons/alloc.cc: Only run test for
C++11 and C++14.
* testsuite/30_threads/packaged_task/cons/alloc2.cc: Likewise.
* testsuite/30_threads/packaged_task/cons/alloc_min.cc: Likewise.
* testsuite/30_threads/packaged_task/uses_allocator.cc: Likewise.
From-SVN: r271582
As well as simpifying the code by removing duplication, this means that
we only need to touch std::__invoke_r if we need to implement changes to
INVOKE<R>, such as those in P0932R0.
* include/bits/std_function.h (_Simple_type_wrapper): Remove.
(_Function_handler): Remove partial specializations for void return
types and pointers to member.
(_Function_handler::_M_manager): Adapt to removal of
_Simple_type_wrapper.
(_Function_handler::_M_invoke): Use __invoke_r instead of __invoke.
* include/std/functional (_Bind_result::__enable_if_void)
(_Bind_result::__disable_if_void): Remove sfinae helpers.
(_Bind_result::__call): Use __invoke_r and remove overloads for void
return types.
* include/std/future (__future_base::_Task_state::_M_run)
(__future_base::_Task_state::_M_run_delayed): Use __invoke_r and
change return type of lambda expressions.
From-SVN: r271174
* include/std/future (__constrain_pkgdtask): Replace with ...
(packaged_task::__not_same): New alias template, using
__remove_cvref_t instead of decay.
* include/std/thread (thread::__not_same): Add comment.
From-SVN: r261618
PR libstdc++/80316
* include/std/future (_State_baseV2::_Setter::operator()): Remove
_S_check calls that are done after the pointer to the shared state is
already dereferenced.
(_State_baseV2::_Setter<_Res, void>): Define specialization for void
as partial specialization so it can be defined within the definition
of _State_baseV2.
(_State_baseV2::__setter): Call _S_check.
(_State_baseV2::__setter(promise<void>*)): Add overload for use by
promise<void>::set_value and promise<void>::set_value_at_thread_exit.
(promise<T>, promise<T&>, promise<void>): Make _State a friend.
(_State_baseV2::_Setter<void, void>): Remove explicit specialization.
(promise<void>::set_value, promise<void>::set_value_at_thread_exit):
Use new __setter overload.
* testsuite/30_threads/promise/members/at_thread_exit2.cc: New test.
* testsuite/30_threads/promise/members/set_exception.cc: Test
promise<T&> and promise<void> specializations.
* testsuite/30_threads/promise/members/set_exception2.cc: Likewise.
Test for no_state error condition.
* testsuite/30_threads/promise/members/set_value2.cc: Likewise.
From-SVN: r247064
* include/std/functional (_Bind_simple, _Bind_simple_helper)
(__bind_simple): Remove.
* include/std/future: Include <bits/invoke.h> instead of <functional>.
(__future_base::_Task_state::_M_run)
(__future_base::_Task_state::_M_run_delayed): Use lambda expressions
instead of __bind_simple.
(__future_base::_Task_state::_S_maybe_wrap_ref): Remove.
(async): Use thread::__make_invoker instead of __bind_simple.
* include/std/thread: Include <tuple> and <bits/invoke.h> instead of
<functional>.
(thread::_Invoker, thread::__make_invoker): Define helpers to do
INVOKE(DECAY_COPY(f), DECAY_COPY(args)...).
From-SVN: r241093
* include/std/functional (__invoke_impl): New overloads.
(__invoke): Replace with a single function calling __invoke_impl.
(invoke): Add C++17 std::invoke.
(reference_wrapper::operator()): Qualify call to __invoke.
(_Mem_fn_traits_base, _Mem_fn_traits): Remove unused typedefs.
(_Mem_fn_base): Remove unused typedefs and implement call operator in
terms of __invoke.
* include/std/future (__future_base::_Async_state_commonV2): Do not
pass reference_wrapper as object argument to call_once.
* include/std/type_traits (result_of): Define nested __invoke_type.
Handle reference_wrapper as per LWG 2219.
* testsuite/20_util/bind/ref_neg.cc: Adjust dg-error directives.
* testsuite/20_util/function_objects/mem_fn/55463.cc: Remove tests
using member functions of reference_wrapper.
From-SVN: r229290
* include/std/future (future_error(error_code)): Construct base
class with error_code's message.
* src/c++11/future.cc (future_error::what()): Do not call c_str() on
temporary string.
From-SVN: r221236
* config/abi/pre/gnu.ver: Add new exports.
* include/std/condition_variable (notify_all_at_thread_exit): Declare.
(__at_thread_exit_elt): New base class.
* include/std/future: Add comments documenting the implementation.
(__future_base::_State_baseV2::_State_baseV2()): Use brace-or-equal
initializers and define constructor as defaulted.
(__future_base::_State_baseV2::_M_ready): Replace member function
with member variable.
(__future_base::_State_baseV2::_M_set_result): Set _M_ready.
(__future_base::_State_baseV2::_M_set_delayed_result): Define.
(__future_base::_State_baseV2::_M_break_promise): Set _M_ready.
(__future_base::_State_baseV2::_Make_ready): New helper class.
(__future_base::_Deferred_state::_M_has_deferred): Remove requirement
for caller to own mutex.
(__future_base::_Async_state_impl::~_Async_state_impl): Call join
directly.
(__future_base::_Task_state_base::_M_run): Take arguments by
reference.
(__future_base::_Task_state_base::_M_run_delayed): Declare new pure
virtual function.
(__future_base::_Task_state::_M_run_delayed): Define override.
(promise::set_value_at_thread_exit): Define.
(promise::set_exception_at_thread_exit): Define.
(packaged_task::make_ready_at_thread_exit): Define.
* src/c++11/condition_variable.cc (notify_all_at_thread_exit): Define.
* src/c++11/future.cc
(__future_base::_State_baseV2::_Make_ready::_M_set): Define.
* testsuite/30_threads/condition_variable/members/3.cc: New.
* testsuite/30_threads/packaged_task/members/at_thread_exit.cc: New.
* testsuite/30_threads/promise/members/at_thread_exit.cc: New.
From-SVN: r218255
* include/std/future (_State_baseV2::_M_set_result): Pass pointers to
_M_do_set.
(_State_baseV2::_M_do_set): Change parameters to pointers.
(_State_baseV2::_Setter): Change _M_arg from reference to pointer.
(_State_baseV2::__setter): Initialize _Setter with pointers.
(_State_baseV2::__setter(promise<void>*)): Remove overload.
(promise::set_value, promise::set_exception): Pass setter directly
to _M_set_result.
(_State_baseV2::_Task_setter): Add template parameter for callable
type and replace std::function member with pointer to that type.
Change _M_result member from reference to pointer.
(_State_baseV2::_S_task_setter): Change parameter to lvalue reference
and initialize _Task_setter with pointers.
(__location_invariant): Specialize for _Setter and _Task_setter.
From-SVN: r213737
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/bits/allocated_ptr.h (__allocated_ptr, __allocate_guarded):
New RAII utilities for working with allocators.
* include/bits/shared_ptr_base.h (_Sp_counted_deleter): Define
__allocator_type typedef and use new __allocated_ptr type.
(_Sp_counted_ptr_inplace): Likewise.
(__shared_count::__shared_count, __shared_ptr::__shared_ptr): Use
__allocate_guarded to to simplify exception handling.
* include/experimental/any (any::_Manager_alloc::_S_alloc): Likewise.
* include/std/future (_Result_alloc::_M_destroy): Likewise.
(_Result_alloc::_S_allocate_result): Likewise.
* testsuite/20_util/shared_ptr/cons/43820_neg.cc: Adjust line number.
* testsuite/20_util/shared_ptr/cons/void_neg.cc: Likewise.
* testsuite/20_util/shared_ptr/creation/no_rtti.cc: New.
* testsuite/20_util/shared_ptr/creation/alloc.cc: Test allocator
with fancy pointer.
* testsuite/30_threads/promise/cons/alloc.cc: Likewise.
From-SVN: r211996
PR libstdc++/60966
* include/std/future (__future_base::_State_baseV2::_M_set_result):
Pass lock into _M_do_set and hold it until the function returns.
Signal condition variable after call_once completes.
(__future_base::_State_baseV2::_M_do_set): Use lock argument. Do not
signal here.
* testsuite/30_threads/promise/60966.cc: New.
From-SVN: r210556
