[libc++] implement std::jthread

Author: huixie90

libcxx/docs/UsingLibcxx.rst

@@ -48,6 +48,7 @@ when ``-fexperimental-library`` is passed:
 
 * The parallel algorithms library (``<execution>`` and the associated algorithms)
 * ``std::stop_token``, ``std::stop_source`` and ``std::stop_callback``
+* ``std::jthread``
 * ``std::chrono::tzdb`` and related time zone functionality
 * ``std::ranges::join_view``
 

libcxx/include/CMakeLists.txt

@@ -677,6 +677,7 @@ set(files
   __system_error/system_error.h
   __thread/formatter.h
   __thread/id.h
+  __thread/jthread.h
   __thread/poll_with_backoff.h
   __thread/this_thread.h
   __thread/thread.h

libcxx/include/__stop_token/atomic_unique_lock.h

@@ -28,7 +28,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 // and LockedBit is the value of State when the lock bit is set, e.g  1 << 2
 template <class _State, _State _LockedBit>
 class _LIBCPP_AVAILABILITY_SYNC __atomic_unique_lock {
-  static_assert(std::popcount(_LockedBit) == 1, "LockedBit must be an integer where only one bit is set");
+  static_assert(std::__libcpp_popcount(static_cast<unsigned long long>(_LockedBit)) == 1,
+                "LockedBit must be an integer where only one bit is set");
 
   std::atomic<_State>& __state_;
   bool __is_locked_;

libcxx/include/__stop_token/stop_callback.h

@@ -26,6 +26,9 @@
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
@@ -96,4 +99,6 @@ _LIBCPP_AVAILABILITY_SYNC stop_callback(stop_token, _Callback) -> stop_callback<
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)

libcxx/include/__stop_token/stop_state.h

@@ -14,9 +14,9 @@
 #include <__config>
 #include <__stop_token/atomic_unique_lock.h>
 #include <__stop_token/intrusive_list_view.h>
+#include <__thread/id.h>
 #include <atomic>
 #include <cstdint>
-#include <thread>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -63,7 +63,7 @@ class __stop_state {
   using __callback_list      = __intrusive_list_view<__stop_callback_base>;
 
   __callback_list __callback_list_;
-  thread::id __requesting_thread_;
+  __thread_id __requesting_thread_;
 
 public:
   _LIBCPP_HIDE_FROM_ABI __stop_state() noexcept = default;

libcxx/include/__thread/jthread.h

@@ -0,0 +1,130 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___THREAD_JTHREAD_H
+#define _LIBCPP___THREAD_JTHREAD_H
+
+#include <__availability>
+#include <__config>
+#include <__functional/invoke.h>
+#include <__stop_token/stop_source.h>
+#include <__stop_token/stop_token.h>
+#include <__thread/thread.h>
+#include <__threading_support>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_constructible.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/remove_cvref.h>
+#include <__utility/forward.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class _LIBCPP_AVAILABILITY_SYNC jthread {
+public:
+  // types
+  using id                 = thread::id;
+  using native_handle_type = thread::native_handle_type;
+
+  // [thread.jthread.cons], constructors, move, and assignment
+  _LIBCPP_HIDE_FROM_ABI jthread() noexcept : __stop_source_(std::nostopstate) {}
+
+  template <class _Fun, class... _Args>
+  _LIBCPP_HIDE_FROM_ABI explicit jthread(_Fun&& __fun, _Args&&... __args)
+    requires(!std::is_same_v<remove_cvref_t<_Fun>, jthread>)
+      : __stop_source_(),
+        __thread_(__init_thread(__stop_source_, std::forward<_Fun>(__fun), std::forward<_Args>(__args)...)) {
+    static_assert(is_constructible_v<decay_t<_Fun>, _Fun>);
+    static_assert((is_constructible_v<decay_t<_Args>, _Args> && ...));
+    static_assert(is_invocable_v<decay_t<_Fun>, decay_t<_Args>...> ||
+                  is_invocable_v<decay_t<_Fun>, stop_token, decay_t<_Args>...>);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI ~jthread() {
+    if (joinable()) {
+      request_stop();
+      join();
+    }
+  }
+
+  jthread(const jthread&) = delete;
+
+  _LIBCPP_HIDE_FROM_ABI jthread(jthread&&) noexcept = default;
+
+  jthread& operator=(const jthread&) = delete;
+
+  _LIBCPP_HIDE_FROM_ABI jthread& operator=(jthread&& __other) noexcept {
+    if (this != &__other) {
+      if (joinable()) {
+        request_stop();
+        join();
+      }
+      __stop_source_ = std::move(__other.__stop_source_);
+      __thread_      = std::move(__other.__thread_);
+    }
+
+    return *this;
+  }
+
+  // [thread.jthread.mem], members
+  _LIBCPP_HIDE_FROM_ABI void swap(jthread& __other) noexcept {
+    std::swap(__stop_source_, __other.__stop_source_);
+    std::swap(__thread_, __other.__thread_);
+  }
+
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool joinable() const noexcept { return get_id() != id(); }
+
+  _LIBCPP_HIDE_FROM_ABI void join() { __thread_.join(); }
+
+  _LIBCPP_HIDE_FROM_ABI void detach() { __thread_.detach(); }
+
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI id get_id() const noexcept { return __thread_.get_id(); }
+
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() { return __thread_.native_handle(); }
+
+  // [thread.jthread.stop], stop token handling
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI stop_source get_stop_source() noexcept { return __stop_source_; }
+
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI stop_token get_stop_token() const noexcept { return __stop_source_.get_token(); }
+
+  _LIBCPP_HIDE_FROM_ABI bool request_stop() noexcept { return __stop_source_.request_stop(); }
+
+  // [thread.jthread.special], specialized algorithms
+  _LIBCPP_HIDE_FROM_ABI friend void swap(jthread& __lhs, jthread& __rhs) noexcept { __lhs.swap(__rhs); }
+
+  // [thread.jthread.static], static members
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static unsigned int hardware_concurrency() noexcept {
+    return thread::hardware_concurrency();
+  }
+
+private:
+  template <class _Fun, class... _Args>
+  _LIBCPP_HIDE_FROM_ABI static thread __init_thread(const stop_source& __ss, _Fun&& __fun, _Args&&... __args) {
+    if constexpr (is_invocable_v<decay_t<_Fun>, stop_token, decay_t<_Args>...>) {
+      return thread(std::forward<_Fun>(__fun), __ss.get_token(), std::forward<_Args>(__args)...);
+    } else {
+      return thread(std::forward<_Fun>(__fun), std::forward<_Args>(__args)...);
+    }
+  }
+
+  stop_source __stop_source_;
+  thread __thread_;
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
+
+#endif // _LIBCPP___THREAD_JTHREAD_H

libcxx/include/module.modulemap.in

@@ -1789,6 +1789,10 @@ module std_private_system_error_system_error    [system] { header "__system_erro
 
 module std_private_thread_formatter            [system] { header "__thread/formatter.h" }
 module std_private_thread_id                   [system] { header "__thread/id.h" }
+module std_private_thread_jthread              [system] {
+  header "__thread/jthread.h"
+  export *
+}
 module std_private_thread_poll_with_backoff    [system] { header "__thread/poll_with_backoff.h" }
 module std_private_thread_this_thread          [system] { header "__thread/this_thread.h" }
 module std_private_thread_thread               [system] {

libcxx/include/thread

@@ -90,6 +90,7 @@ void sleep_for(const chrono::duration<Rep, Period>& rel_time);
 #include <__availability>
 #include <__config>
 #include <__thread/formatter.h>
+#include <__thread/jthread.h>
 #include <__thread/this_thread.h>
 #include <__thread/thread.h>
 #include <__threading_support>

libcxx/modules/std/thread.inc

@@ -15,7 +15,9 @@ export namespace std {
   using std::swap;
 
   // [thread.jthread.class], class jthread
-  // using std::jthread;
+#  if !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
+  using std::jthread;
+#  endif
 
   // [thread.thread.this], namespace this_thread
   namespace this_thread {

libcxx/test/libcxx/transitive_includes/cxx03.csv

@@ -805,9 +805,9 @@ stop_token cstddef
 stop_token cstdint
 stop_token cstring
 stop_token ctime
+stop_token iosfwd
 stop_token limits
 stop_token ratio
-stop_token thread
 stop_token type_traits
 stop_token version
 streambuf cstdint
@@ -867,6 +867,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread atomic
 thread cerrno
 thread chrono
 thread compare

libcxx/test/libcxx/transitive_includes/cxx11.csv

@@ -811,9 +811,9 @@ stop_token cstddef
 stop_token cstdint
 stop_token cstring
 stop_token ctime
+stop_token iosfwd
 stop_token limits
 stop_token ratio
-stop_token thread
 stop_token type_traits
 stop_token version
 streambuf cstdint
@@ -873,6 +873,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread atomic
 thread cerrno
 thread chrono
 thread compare

libcxx/test/libcxx/transitive_includes/cxx14.csv

@@ -813,9 +813,9 @@ stop_token cstddef
 stop_token cstdint
 stop_token cstring
 stop_token ctime
+stop_token iosfwd
 stop_token limits
 stop_token ratio
-stop_token thread
 stop_token type_traits
 stop_token version
 streambuf cstdint
@@ -875,6 +875,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread atomic
 thread cerrno
 thread chrono
 thread compare

libcxx/test/libcxx/transitive_includes/cxx17.csv

@@ -813,9 +813,9 @@ stop_token cstddef
 stop_token cstdint
 stop_token cstring
 stop_token ctime
+stop_token iosfwd
 stop_token limits
 stop_token ratio
-stop_token thread
 stop_token type_traits
 stop_token version
 streambuf cstdint
@@ -875,6 +875,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread atomic
 thread cerrno
 thread chrono
 thread compare

libcxx/test/libcxx/transitive_includes/cxx20.csv

@@ -818,9 +818,9 @@ stop_token cstddef
 stop_token cstdint
 stop_token cstring
 stop_token ctime
+stop_token iosfwd
 stop_token limits
 stop_token ratio
-stop_token thread
 stop_token type_traits
 stop_token version
 streambuf cstdint
@@ -880,6 +880,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread atomic
 thread cerrno
 thread compare
 thread cstddef

libcxx/test/libcxx/transitive_includes/cxx23.csv

@@ -582,9 +582,9 @@ stop_token cstddef
 stop_token cstdint
 stop_token cstring
 stop_token ctime
+stop_token iosfwd
 stop_token limits
 stop_token ratio
-stop_token thread
 stop_token version
 streambuf cstdint
 streambuf ios
@@ -627,6 +627,7 @@ system_error stdexcept
 system_error string
 system_error version
 thread array
+thread atomic
 thread cerrno
 thread compare
 thread cstddef

libcxx/test/libcxx/transitive_includes/cxx26.csv

@@ -582,9 +582,9 @@ stop_token cstddef
 stop_token cstdint
 stop_token cstring
 stop_token ctime
+stop_token iosfwd
 stop_token limits
 stop_token ratio
-stop_token thread
 stop_token version
 streambuf cstdint
 streambuf ios
@@ -627,6 +627,7 @@ system_error stdexcept
 system_error string
 system_error version
 thread array
+thread atomic
 thread cerrno
 thread compare
 thread cstddef