text: /* GLIB - Library of useful routines for C programming
   * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
   *
   * gthread.c: MT safety related functions
   * Copyright 1998 Sebastian Wilhelmi; University of Karlsruhe
   *                Owen Taylor
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, see <http://www.gnu.org/licenses/>.
   */
  
  /* Prelude {{{1 ----------------------------------------------------------- */
  
  /*
   * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
   * file for a list of people on the GLib Team.  See the ChangeLog
   * files for a list of changes.  These files are distributed with
   * GLib at ftp://ftp.gtk.org/pub/gtk/.
   */
  
  /*
   * MT safe
   */
  
  /* implement gthread.h's inline functions */
  #define G_IMPLEMENT_INLINES 1
  #define __G_THREAD_C__
  
  #include "config.h"
  
  #include "gthread.h"
  #include "gthreadprivate.h"
  
  #include <string.h>
  
  #ifdef G_OS_UNIX
  #include <unistd.h>
  #endif
  
  #ifndef G_OS_WIN32
  #include <sys/time.h>
  #include <time.h>
  #else
  #include <windows.h>
  #endif /* G_OS_WIN32 */
  
  #include "gslice.h"
  #include "gstrfuncs.h"
  #include "gtestutils.h"
  #include "glib_trace.h"
  
  /**
   * SECTION:threads
   * @title: Threads
   * @short_description: portable support for threads, mutexes, locks,
   *     conditions and thread private data
   * @see_also: #GThreadPool, #GAsyncQueue
   *
   * Threads act almost like processes, but unlike processes all threads
   * of one process share the same memory. This is good, as it provides
   * easy communication between the involved threads via this shared
   * memory, and it is bad, because strange things (so called
   * "Heisenbugs") might happen if the program is not carefully designed.
   * In particular, due to the concurrent nature of threads, no
   * assumptions on the order of execution of code running in different
   * threads can be made, unless order is explicitly forced by the
   * programmer through synchronization primitives.
   *
   * The aim of the thread-related functions in GLib is to provide a
   * portable means for writing multi-threaded software. There are
   * primitives for mutexes to protect the access to portions of memory
   * (#GMutex, #GRecMutex and #GRWLock). There is a facility to use
   * individual bits for locks (g_bit_lock()). There are primitives
   * for condition variables to allow synchronization of threads (#GCond).
   * There are primitives for thread-private data - data that every
   * thread has a private instance of (#GPrivate). There are facilities
   * for one-time initialization (#GOnce, g_once_init_enter()). Finally,
   * there are primitives to create and manage threads (#GThread).
   *
   * The GLib threading system used to be initialized with g_thread_init().
   * This is no longer necessary. Since version 2.32, the GLib threading
   * system is automatically initialized at the start of your program,
   * and all thread-creation functions and synchronization primitives
   * are available right away.
   *
   * Note that it is not safe to assume that your program has no threads
   * even if you don't call g_thread_new() yourself. GLib and GIO can
   * and will create threads for their own purposes in some cases, such
   * as when using g_unix_signal_source_new() or when using GDBus.
   *
   * Originally, UNIX did not have threads, and therefore some traditional
   * UNIX APIs are problematic in threaded programs. Some notable examples
   * are
   * 
   * - C library functions that return data in statically allocated
   *   buffers, such as strtok() or strerror(). For many of these,
   *   there are thread-safe variants with a _r suffix, or you can
   *   look at corresponding GLib APIs (like g_strsplit() or g_strerror()).
   *
   * - The functions setenv() and unsetenv() manipulate the process
   *   environment in a not thread-safe way, and may interfere with getenv()
   *   calls in other threads. Note that getenv() calls may be hidden behind
   *   other APIs. For example, GNU gettext() calls getenv() under the
   *   covers. In general, it is best to treat the environment as readonly.
   *   If you absolutely have to modify the environment, do it early in
   *   main(), when no other threads are around yet.
   *
   * - The setlocale() function changes the locale for the entire process,
   *   affecting all threads. Temporary changes to the locale are often made
   *   to change the behavior of string scanning or formatting functions
   *   like scanf() or printf(). GLib offers a number of string APIs
   *   (like g_ascii_formatd() or g_ascii_strtod()) that can often be
   *   used as an alternative. Or you can use the uselocale() function
   *   to change the locale only for the current thread.
   *
   * - The fork() function only takes the calling thread into the child's
   *   copy of the process image. If other threads were executing in critical
   *   sections they could have left mutexes locked which could easily
   *   cause deadlocks in the new child. For this reason, you should
   *   call exit() or exec() as soon as possible in the child and only
   *   make signal-safe library calls before that.
   *
   * - The daemon() function uses fork() in a way contrary to what is
   *   described above. It should not be used with GLib programs.
   *
   * GLib itself is internally completely thread-safe (all global data is
   * automatically locked), but individual data structure instances are
   * not automatically locked for performance reasons. For example,
   * you must coordinate accesses to the same #GHashTable from multiple
   * threads. The two notable exceptions from this rule are #GMainLoop
   * and #GAsyncQueue, which are thread-safe and need no further
   * application-level locking to be accessed from multiple threads.
   * Most refcounting functions such as g_object_ref() are also thread-safe.
   *
   * A common use for #GThreads is to move a long-running blocking operation out
   * of the main thread and into a worker thread. For GLib functions, such as
   * single GIO operations, this is not necessary, and complicates the code.
   * Instead, the `…_async()` version of the function should be used from the main
   * thread, eliminating the need for locking and synchronisation between multiple
   * threads. If an operation does need to be moved to a worker thread, consider
   * using g_task_run_in_thread(), or a #GThreadPool. #GThreadPool is often a
   * better choice than #GThread, as it handles thread reuse and task queueing;
   * #GTask uses this internally.
   *
   * However, if multiple blocking operations need to be performed in sequence,
   * and it is not possible to use #GTask for them, moving them to a worker thread
   * can clarify the code.
   */
  
  /* G_LOCK Documentation {{{1 ---------------------------------------------- */
  
  /**
   * G_LOCK_DEFINE:
   * @name: the name of the lock
   *
   * The #G_LOCK_ macros provide a convenient interface to #GMutex.
   * #G_LOCK_DEFINE defines a lock. It can appear in any place where
   * variable definitions may appear in programs, i.e. in the first block
   * of a function or outside of functions. The @name parameter will be
   * mangled to get the name of the #GMutex. This means that you
   * can use names of existing variables as the parameter - e.g. the name
   * of the variable you intend to protect with the lock. Look at our
   * give_me_next_number() example using the #G_LOCK macros:
   *
   * Here is an example for using the #G_LOCK convenience macros:
   * |[<!-- language="C" --> 
   *   G_LOCK_DEFINE (current_number);
   *
   *   int
   *   give_me_next_number (void)
   *   {
   *     static int current_number = 0;
   *     int ret_val;
   *
   *     G_LOCK (current_number);
   *     ret_val = current_number = calc_next_number (current_number);
   *     G_UNLOCK (current_number);
   *
   *     return ret_val;
   *   }
   * ]|
   */
  
  /**
   * G_LOCK_DEFINE_STATIC:
   * @name: the name of the lock
   *
   * This works like #G_LOCK_DEFINE, but it creates a static object.
   */
  
  /**
   * G_LOCK_EXTERN:
   * @name: the name of the lock
   *
   * This declares a lock, that is defined with #G_LOCK_DEFINE in another
   * module.
   */
  
  /**
   * G_LOCK:
   * @name: the name of the lock
   *
   * Works like g_mutex_lock(), but for a lock defined with
   * #G_LOCK_DEFINE.
   */
  
  /**
   * G_TRYLOCK:
   * @name: the name of the lock
   *
   * Works like g_mutex_trylock(), but for a lock defined with
   * #G_LOCK_DEFINE.
   *
   * Returns: %TRUE, if the lock could be locked.
   */
  
  /**
   * G_UNLOCK:
   * @name: the name of the lock
   *
   * Works like g_mutex_unlock(), but for a lock defined with
   * #G_LOCK_DEFINE.
   */
  
  /* GMutex Documentation {{{1 ------------------------------------------ */
  
  /**
   * GMutex:
   *
   * The #GMutex struct is an opaque data structure to represent a mutex
   * (mutual exclusion). It can be used to protect data against shared
   * access.
   *
   * Take for example the following function:
   * |[<!-- language="C" --> 
   *   int
   *   give_me_next_number (void)
   *   {
   *     static int current_number = 0;
   *
   *     // now do a very complicated calculation to calculate the new
   *     // number, this might for example be a random number generator
   *     current_number = calc_next_number (current_number);
   *
   *     return current_number;
   *   }
   * ]|
   * It is easy to see that this won't work in a multi-threaded
   * application. There current_number must be protected against shared
   * access. A #GMutex can be used as a solution to this problem:
   * |[<!-- language="C" --> 
   *   int
   *   give_me_next_number (void)
   *   {
   *     static GMutex mutex;
   *     static int current_number = 0;
   *     int ret_val;
   *
   *     g_mutex_lock (&mutex);
   *     ret_val = current_number = calc_next_number (current_number);
   *     g_mutex_unlock (&mutex);
   *
   *     return ret_val;
   *   }
   * ]|
   * Notice that the #GMutex is not initialised to any particular value.
   * Its placement in static storage ensures that it will be initialised
   * to all-zeros, which is appropriate.
   *
   * If a #GMutex is placed in other contexts (eg: embedded in a struct)
   * then it must be explicitly initialised using g_mutex_init().
   *
   * A #GMutex should only be accessed via g_mutex_ functions.
   */
  
  /* GRecMutex Documentation {{{1 -------------------------------------- */
  
  /**
   * GRecMutex:
   *
   * The GRecMutex struct is an opaque data structure to represent a
   * recursive mutex. It is similar to a #GMutex with the difference
   * that it is possible to lock a GRecMutex multiple times in the same
   * thread without deadlock. When doing so, care has to be taken to
   * unlock the recursive mutex as often as it has been locked.
   *
   * If a #GRecMutex is allocated in static storage then it can be used
   * without initialisation.  Otherwise, you should call
   * g_rec_mutex_init() on it and g_rec_mutex_clear() when done.
   *
   * A GRecMutex should only be accessed with the
   * g_rec_mutex_ functions.
   *
   * Since: 2.32
   */
  
  /* GRWLock Documentation {{{1 ---------------------------------------- */
  
  /**
   * GRWLock:
   *
   * The GRWLock struct is an opaque data structure to represent a
   * reader-writer lock. It is similar to a #GMutex in that it allows
   * multiple threads to coordinate access to a shared resource.
   *
   * The difference to a mutex is that a reader-writer lock discriminates
   * between read-only ('reader') and full ('writer') access. While only
   * one thread at a time is allowed write access (by holding the 'writer'
   * lock via g_rw_lock_writer_lock()), multiple threads can gain
   * simultaneous read-only access (by holding the 'reader' lock via
   * g_rw_lock_reader_lock()).
   *
   * It is unspecified whether readers or writers have priority in acquiring the
   * lock when a reader already holds the lock and a writer is queued to acquire
   * it.
   *
   * Here is an example for an array with access functions:
   * |[<!-- language="C" --> 
   *   GRWLock lock;
   *   GPtrArray *array;
   *
   *   gpointer
   *   my_array_get (guint index)
   *   {
   *     gpointer retval = NULL;
   *
   *     if (!array)
   *       return NULL;
   *
   *     g_rw_lock_reader_lock (&lock);
   *     if (index < array->len)
   *       retval = g_ptr_array_index (array, index);
   *     g_rw_lock_reader_unlock (&lock);
   *
   *     return retval;
   *   }
   *
   *   void
   *   my_array_set (guint index, gpointer data)
   *   {
   *     g_rw_lock_writer_lock (&lock);
   *
   *     if (!array)
   *       array = g_ptr_array_new ();
   *
   *     if (index >= array->len)
   *       g_ptr_array_set_size (array, index+1);
   *     g_ptr_array_index (array, index) = data;
   *
   *     g_rw_lock_writer_unlock (&lock);
   *   }
   *  ]|
   * This example shows an array which can be accessed by many readers
   * (the my_array_get() function) simultaneously, whereas the writers
   * (the my_array_set() function) will only be allowed one at a time
   * and only if no readers currently access the array. This is because
   * of the potentially dangerous resizing of the array. Using these
   * functions is fully multi-thread safe now.
   *
   * If a #GRWLock is allocated in static storage then it can be used
   * without initialisation.  Otherwise, you should call
   * g_rw_lock_init() on it and g_rw_lock_clear() when done.
   *
   * A GRWLock should only be accessed with the g_rw_lock_ functions.
   *
   * Since: 2.32
   */
  
  /* GCond Documentation {{{1 ------------------------------------------ */
  
  /**
   * GCond:
   *
   * The #GCond struct is an opaque data structure that represents a
   * condition. Threads can block on a #GCond if they find a certain
   * condition to be false. If other threads change the state of this
   * condition they signal the #GCond, and that causes the waiting
   * threads to be woken up.
   *
   * Consider the following example of a shared variable.  One or more
   * threads can wait for data to be published to the variable and when
   * another thread publishes the data, it can signal one of the waiting
   * threads to wake up to collect the data.
   *
   * Here is an example for using GCond to block a thread until a condition
   * is satisfied:
   * |[<!-- language="C" --> 
   *   gpointer current_data = NULL;
   *   GMutex data_mutex;
   *   GCond data_cond;
   *
   *   void
   *   push_data (gpointer data)
   *   {
   *     g_mutex_lock (&data_mutex);
   *     current_data = data;
   *     g_cond_signal (&data_cond);
   *     g_mutex_unlock (&data_mutex);
   *   }
   *
   *   gpointer
   *   pop_data (void)
   *   {
   *     gpointer data;
   *
   *     g_mutex_lock (&data_mutex);
   *     while (!current_data)
   *       g_cond_wait (&data_cond, &data_mutex);
   *     data = current_data;
   *     current_data = NULL;
   *     g_mutex_unlock (&data_mutex);
   *
   *     return data;
   *   }
   * ]|
   * Whenever a thread calls pop_data() now, it will wait until
   * current_data is non-%NULL, i.e. until some other thread
   * has called push_data().
   *
   * The example shows that use of a condition variable must always be
   * paired with a mutex.  Without the use of a mutex, there would be a
   * race between the check of @current_data by the while loop in
   * pop_data() and waiting. Specifically, another thread could set
   * @current_data after the check, and signal the cond (with nobody
   * waiting on it) before the first thread goes to sleep. #GCond is
   * specifically useful for its ability to release the mutex and go
   * to sleep atomically.
   *
   * It is also important to use the g_cond_wait() and g_cond_wait_until()
   * functions only inside a loop which checks for the condition to be
   * true.  See g_cond_wait() for an explanation of why the condition may
   * not be true even after it returns.
   *
   * If a #GCond is allocated in static storage then it can be used
   * without initialisation.  Otherwise, you should call g_cond_init()
   * on it and g_cond_clear() when done.
   *
   * A #GCond should only be accessed via the g_cond_ functions.
   */
  
  /* GThread Documentation {{{1 ---------------------------------------- */
  
  /**
   * GThread:
   *
   * The #GThread struct represents a running thread. This struct
   * is returned by g_thread_new() or g_thread_try_new(). You can
   * obtain the #GThread struct representing the current thread by
   * calling g_thread_self().
   *
   * GThread is refcounted, see g_thread_ref() and g_thread_unref().
   * The thread represented by it holds a reference while it is running,
   * and g_thread_join() consumes the reference that it is given, so
   * it is normally not necessary to manage GThread references
   * explicitly.
   *
   * The structure is opaque -- none of its fields may be directly
   * accessed.
   */
  
  /**
   * GThreadFunc:
   * @data: data passed to the thread
   *
   * Specifies the type of the @func functions passed to g_thread_new()
   * or g_thread_try_new().
   *
   * Returns: the return value of the thread
   */
  
  /**
   * g_thread_supported:
   *
   * This macro returns %TRUE if the thread system is initialized,
   * and %FALSE if it is not.
   *
   * For language bindings, g_thread_get_initialized() provides
   * the same functionality as a function.
   *
   * Returns: %TRUE, if the thread system is initialized
   */
  
  /* GThreadError {{{1 ------------------------------------------------------- */
  /**
   * GThreadError:
   * @G_THREAD_ERROR_AGAIN: a thread couldn't be created due to resource
   *                        shortage. Try again later.
   *
   * Possible errors of thread related functions.
   **/
  
  /**
   * G_THREAD_ERROR:
   *
   * The error domain of the GLib thread subsystem.
   **/
  G_DEFINE_QUARK (g_thread_error, g_thread_error)
  
  /* Local Data {{{1 -------------------------------------------------------- */
  
  static GMutex    g_once_mutex;
  static GCond     g_once_cond;
  static GSList   *g_once_init_list = NULL;
  
  static void g_thread_cleanup (gpointer data);
  static GPrivate     g_thread_specific_private = G_PRIVATE_INIT (g_thread_cleanup);
  
  /*
   * g_private_set_alloc0:
   * @key: a #GPrivate
   * @size: size of the allocation, in bytes
   *
   * Sets the thread local variable @key to have a newly-allocated and zero-filled
   * value of given @size, and returns a pointer to that memory. Allocations made
   * using this API will be suppressed in valgrind: it is intended to be used for
   * one-time allocations which are known to be leaked, such as those for
   * per-thread initialisation data. Otherwise, this function behaves the same as
   * g_private_set().
   *
   * Returns: (transfer full): new thread-local heap allocation of size @size
   * Since: 2.60
   */
  /*< private >*/
  gpointer
  g_private_set_alloc0 (GPrivate *key,
                        gsize     size)
  {
    gpointer allocated = g_malloc0 (size);
  
    g_private_set (key, allocated);
  
    return g_steal_pointer (&allocated);
  }
  
  /* GOnce {{{1 ------------------------------------------------------------- */
  
  /**
   * GOnce:
   * @status: the status of the #GOnce
   * @retval: the value returned by the call to the function, if @status
   *          is %G_ONCE_STATUS_READY
   *
   * A #GOnce struct controls a one-time initialization function. Any
   * one-time initialization function must have its own unique #GOnce
   * struct.
   *
   * Since: 2.4
   */
  
  /**
   * G_ONCE_INIT:
   *
   * A #GOnce must be initialized with this macro before it can be used.
   *
   * |[<!-- language="C" --> 
   *   GOnce my_once = G_ONCE_INIT;
   * ]|
   *
   * Since: 2.4
   */
  
  /**
   * GOnceStatus:
   * @G_ONCE_STATUS_NOTCALLED: the function has not been called yet.
   * @G_ONCE_STATUS_PROGRESS: the function call is currently in progress.
   * @G_ONCE_STATUS_READY: the function has been called.
   *
   * The possible statuses of a one-time initialization function
   * controlled by a #GOnce struct.
   *
   * Since: 2.4
   */
  
  /**
   * g_once:
   * @once: a #GOnce structure
   * @func: the #GThreadFunc function associated to @once. This function
   *        is called only once, regardless of the number of times it and
   *        its associated #GOnce struct are passed to g_once().
   * @arg: data to be passed to @func
   *
   * The first call to this routine by a process with a given #GOnce
   * struct calls @func with the given argument. Thereafter, subsequent
   * calls to g_once()  with the same #GOnce struct do not call @func
   * again, but return the stored result of the first call. On return
   * from g_once(), the status of @once will be %G_ONCE_STATUS_READY.
   *
   * For example, a mutex or a thread-specific data key must be created
   * exactly once. In a threaded environment, calling g_once() ensures
   * that the initialization is serialized across multiple threads.
   *
   * Calling g_once() recursively on the same #GOnce struct in
   * @func will lead to a deadlock.
   *
   * |[<!-- language="C" --> 
   *   gpointer
   *   get_debug_flags (void)
   *   {
   *     static GOnce my_once = G_ONCE_INIT;
   *
   *     g_once (&my_once, parse_debug_flags, NULL);
   *
   *     return my_once.retval;
   *   }
   * ]|
   *
   * Since: 2.4
   */
  gpointer
  g_once_impl (GOnce       *once,
  	     GThreadFunc  func,
  	     gpointer     arg)
  {
    g_mutex_lock (&g_once_mutex);
  
    while (once->status == G_ONCE_STATUS_PROGRESS)
      g_cond_wait (&g_once_cond, &g_once_mutex);
  
    if (once->status != G_ONCE_STATUS_READY)
      {
        once->status = G_ONCE_STATUS_PROGRESS;
        g_mutex_unlock (&g_once_mutex);
  
        once->retval = func (arg);
  
        g_mutex_lock (&g_once_mutex);
        once->status = G_ONCE_STATUS_READY;
        g_cond_broadcast (&g_once_cond);
      }
  
    g_mutex_unlock (&g_once_mutex);
  
    return once->retval;
  }
  
  /**
   * g_once_init_enter:
   * @location: (not nullable): location of a static initializable variable
   *    containing 0
   *
   * Function to be called when starting a critical initialization
   * section. The argument @location must point to a static
   * 0-initialized variable that will be set to a value other than 0 at
   * the end of the initialization section. In combination with
   * g_once_init_leave() and the unique address @value_location, it can
   * be ensured that an initialization section will be executed only once
   * during a program's life time, and that concurrent threads are
   * blocked until initialization completed. To be used in constructs
   * like this:
   *
   * |[<!-- language="C" --> 
   *   static gsize initialization_value = 0;
   *
   *   if (g_once_init_enter (&initialization_value))
   *     {
   *       gsize setup_value = 42; // initialization code here
   *
   *       g_once_init_leave (&initialization_value, setup_value);
   *     }
   *
   *   // use initialization_value here
   * ]|
   *
   * Returns: %TRUE if the initialization section should be entered,
   *     %FALSE and blocks otherwise
   *
   * Since: 2.14
   */
  gboolean
  (g_once_init_enter) (volatile void *location)
  {
    volatile gsize *value_location = location;
    gboolean need_init = FALSE;
    g_mutex_lock (&g_once_mutex);
    if (g_atomic_pointer_get (value_location) == NULL)
      {
        if (!g_slist_find (g_once_init_list, (void*) value_location))
          {
            need_init = TRUE;
            g_once_init_list = g_slist_prepend (g_once_init_list, (void*) value_location);
          }
        else
          do
            g_cond_wait (&g_once_cond, &g_once_mutex);
          while (g_slist_find (g_once_init_list, (void*) value_location));
      }
    g_mutex_unlock (&g_once_mutex);
    return need_init;
  }
  
  /**
   * g_once_init_leave:
   * @location: (not nullable): location of a static initializable variable
   *    containing 0
   * @result: new non-0 value for *@value_location
   *
   * Counterpart to g_once_init_enter(). Expects a location of a static
   * 0-initialized initialization variable, and an initialization value
   * other than 0. Sets the variable to the initialization value, and
   * releases concurrent threads blocking in g_once_init_enter() on this
   * initialization variable.
   *
   * Since: 2.14
   */
  void
  (g_once_init_leave) (volatile void *location,
                       gsize          result)
  {
    volatile gsize *value_location = location;
  
    g_return_if_fail (g_atomic_pointer_get (value_location) == NULL);
    g_return_if_fail (result != 0);
  
    g_atomic_pointer_set (value_location, result);
    g_mutex_lock (&g_once_mutex);
    g_return_if_fail (g_once_init_list != NULL);
    g_once_init_list = g_slist_remove (g_once_init_list, (void*) value_location);
    g_cond_broadcast (&g_once_cond);
    g_mutex_unlock (&g_once_mutex);
  }
  
  /* GThread {{{1 -------------------------------------------------------- */
  
  /**
   * g_thread_ref:
   * @thread: a #GThread
   *
   * Increase the reference count on @thread.
   *
   * Returns: a new reference to @thread
   *
   * Since: 2.32
   */
  GThread *
  g_thread_ref (GThread *thread)
  {
    GRealThread *real = (GRealThread *) thread;
  
    g_atomic_int_inc (&real->ref_count);
  
    return thread;
  }
  
  /**
   * g_thread_unref:
   * @thread: a #GThread
   *
   * Decrease the reference count on @thread, possibly freeing all
   * resources associated with it.
   *
   * Note that each thread holds a reference to its #GThread while
   * it is running, so it is safe to drop your own reference to it
   * if you don't need it anymore.
   *
   * Since: 2.32
   */
  void
  g_thread_unref (GThread *thread)
  {
    GRealThread *real = (GRealThread *) thread;
  
    if (g_atomic_int_dec_and_test (&real->ref_count))
      {
        if (real->ours)
          g_system_thread_free (real);
        else
          g_slice_free (GRealThread, real);
      }
  }
  
  static void
  g_thread_cleanup (gpointer data)
  {
    g_thread_unref (data);
  }
  
  gpointer
  g_thread_proxy (gpointer data)
  {
    GRealThread* thread = data;
  
    g_assert (data);
    g_private_set (&g_thread_specific_private, data);
  
    TRACE (GLIB_THREAD_SPAWNED (thread->thread.func, thread->thread.data,
                                thread->name));
  
    if (thread->name)
      {
        g_system_thread_set_name (thread->name);
        g_free (thread->name);
        thread->name = NULL;
      }
  
    thread->retval = thread->thread.func (thread->thread.data);
  
    return NULL;
  }
  
  /**
   * g_thread_new:
   * @name: (nullable): an (optional) name for the new thread
   * @func: a function to execute in the new thread
   * @data: an argument to supply to the new thread
   *
   * This function creates a new thread. The new thread starts by invoking
   * @func with the argument data. The thread will run until @func returns
   * or until g_thread_exit() is called from the new thread. The return value
   * of @func becomes the return value of the thread, which can be obtained
   * with g_thread_join().
   *
   * The @name can be useful for discriminating threads in a debugger.
   * It is not used for other purposes and does not have to be unique.
   * Some systems restrict the length of @name to 16 bytes.
   *
   * If the thread can not be created the program aborts. See
   * g_thread_try_new() if you want to attempt to deal with failures.
   *
   * If you are using threads to offload (potentially many) short-lived tasks,
   * #GThreadPool may be more appropriate than manually spawning and tracking
   * multiple #GThreads.
   *
   * To free the struct returned by this function, use g_thread_unref().
   * Note that g_thread_join() implicitly unrefs the #GThread as well.
   *
   * Returns: the new #GThread
   *
   * Since: 2.32
   */
  GThread *
  g_thread_new (const gchar *name,
                GThreadFunc  func,
                gpointer     data)
  {
    GError *error = NULL;
    GThread *thread;
  
    thread = g_thread_new_internal (name, g_thread_proxy, func, data, 0, &error);
  
    if G_UNLIKELY (thread == NULL)
      g_error ("creating thread '%s': %s", name ? name : "", error->message);
  
    return thread;
  }
  
  /**
   * g_thread_try_new:
   * @name: (nullable): an (optional) name for the new thread
   * @func: a function to execute in the new thread
   * @data: an argument to supply to the new thread
   * @error: return location for error, or %NULL
   *
   * This function is the same as g_thread_new() except that
   * it allows for the possibility of failure.
   *
   * If a thread can not be created (due to resource limits),
   * @error is set and %NULL is returned.
   *
   * Returns: the new #GThread, or %NULL if an error occurred
   *
   * Since: 2.32
   */
  GThread *
  g_thread_try_new (const gchar  *name,
                    GThreadFunc   func,
                    gpointer      data,
                    GError      **error)
  {
    return g_thread_new_internal (name, g_thread_proxy, func, data, 0, error);
  }
  
  GThread *
  g_thread_new_internal (const gchar   *name,
                         GThreadFunc    proxy,
                         GThreadFunc    func,
                         gpointer       data,
                         gsize          stack_size,
                         GError       **error)
  {
    g_return_val_if_fail (func != NULL, NULL);
  
    return (GThread*) g_system_thread_new (proxy, stack_size, name,
                                           func, data, error);
  }
  
  /**
   * g_thread_exit:
   * @retval: the return value of this thread
   *
   * Terminates the current thread.
   *
   * If another thread is waiting for us using g_thread_join() then the
   * waiting thread will be woken up and get @retval as the return value
   * of g_thread_join().
   *
   * Calling g_thread_exit() with a parameter @retval is equivalent to
   * returning @retval from the function @func, as given to g_thread_new().
   *
   * You must only call g_thread_exit() from a thread that you created
   * yourself with g_thread_new() or related APIs. You must not call
   * this function from a thread created with another threading library
   * or or from within a #GThreadPool.
   */
  void
  g_thread_exit (gpointer retval)
  {
    GRealThread* real = (GRealThread*) g_thread_self ();
  
    if G_UNLIKELY (!real->ours)
      g_error ("attempt to g_thread_exit() a thread not created by GLib");
  
    real->retval = retval;
  
    g_system_thread_exit ();
  }
  
  /**
   * g_thread_join:
   * @thread: a #GThread
   *
   * Waits until @thread finishes, i.e. the function @func, as
   * given to g_thread_new(), returns or g_thread_exit() is called.
   * If @thread has already terminated, then g_thread_join()
   * returns immediately.
   *
   * Any thread can wait for any other thread by calling g_thread_join(),
   * not just its 'creator'. Calling g_thread_join() from multiple threads
   * for the same @thread leads to undefined behaviour.
   *
   * The value returned by @func or given to g_thread_exit() is
   * returned by this function.
   *
   * g_thread_join() consumes the reference to the passed-in @thread.
   * This will usually cause the #GThread struct and associated resources
   * to be freed. Use g_thread_ref() to obtain an extra reference if you
   * want to keep the GThread alive beyond the g_thread_join() call.
   *
   * Returns: the return value of the thread
   */
  gpointer
  g_thread_join (GThread *thread)
  {
    GRealThread *real = (GRealThread*) thread;
    gpointer retval;
  
    g_return_val_if_fail (thread, NULL);
    g_return_val_if_fail (real->ours, NULL);
  
    g_system_thread_wait (real);
  
    retval = real->retval;
  
    /* Just to make sure, this isn't used any more */
    thread->joinable = 0;
  
    g_thread_unref (thread);
  
    return retval;
  }
  
  /**
   * g_thread_self:
   *
   * This function returns the #GThread corresponding to the
   * current thread. Note that this function does not increase
   * the reference count of the returned struct.
   *
   * This function will return a #GThread even for threads that
   * were not created by GLib (i.e. those created by other threading
   * APIs). This may be useful for thread identification purposes
   * (i.e. comparisons) but you must not use GLib functions (such
   * as g_thread_join()) on these threads.
   *
   * Returns: the #GThread representing the current thread
   */
  GThread*
  g_thread_self (void)
  {
    GRealThread* thread = g_private_get (&g_thread_specific_private);
  
    if (!thread)
      {
        /* If no thread data is available, provide and set one.
         * This can happen for the main thread and for threads
         * that are not created by GLib.
         */
        thread = g_slice_new0 (GRealThread);
        thread->ref_count = 1;
  
        g_private_set (&g_thread_specific_private, thread);
      }
  
    return (GThread*) thread;
  }
  
  /**
   * g_get_num_processors:
   *
   * Determine the approximate number of threads that the system will
   * schedule simultaneously for this process.  This is intended to be
   * used as a parameter to g_thread_pool_new() for CPU bound tasks and
   * similar cases.
   *
   * Returns: Number of schedulable threads, always greater than 0
   *
   * Since: 2.36
   */
  guint
  g_get_num_processors (void)
  {
  #ifdef G_OS_WIN32
    unsigned int count;
    SYSTEM_INFO sysinfo;
    DWORD_PTR process_cpus;
    DWORD_PTR system_cpus;
  
    /* This *never* fails, use it as fallback */
    GetNativeSystemInfo (&sysinfo);
    count = (int) sysinfo.dwNumberOfProcessors;
  
    if (GetProcessAffinityMask (GetCurrentProcess (),
                                &process_cpus, &system_cpus))
      {
        unsigned int af_count;
  
        for (af_count = 0; process_cpus != 0; process_cpus >>= 1)
          if (process_cpus & 1)
            af_count++;
  
        /* Prefer affinity-based result, if available */
        if (af_count > 0)
          count = af_count;
      }
  
    if (count > 0)
      return count;
  #elif defined(_SC_NPROCESSORS_ONLN)
    {
      int count;
  
      count = sysconf (_SC_NPROCESSORS_ONLN);
      if (count > 0)
        return count;
    }
  #elif defined HW_NCPU
    {
      int mib[2], count = 0;
      size_t len;
  
      mib[0] = CTL_HW;
      mib[1] = HW_NCPU;
      len = sizeof(count);
  
      if (sysctl (mib, 2, &count, &len, NULL, 0) == 0 && count > 0)
        return count;
    }
  #endif
  
    return 1; /* Fallback */
  }
  
  /* Epilogue {{{1 */
  /* vim: set foldmethod=marker: */
  