* src/thread.c (last_thread_error): New static variable.
(syms_of_threads): Staticpro it.
(record_thread_error, Fthread_last_error): New functions.
(syms_of_threads): Defsubr Fthread_last_error.
* doc/lispref/threads.texi (Basic Thread Functions): Document
thread-last-error.
* test/src/thread-tests.el (thread-errors, thread-signal-early)
(threads-condvar-wait): Test the values returned by
thread-last-error.
* test/src/thread-tests.el (threads-condvar-wait): Revert
previous change. Make sure no other threads from previous
tests are running, to avoid interfering with our thread counts.
* test/src/thread-tests.el (threads-test-condvar-wait): Use
with-mutex instead of emulating it inline.
(threads-condvar-wait): Improve comments. Check that the new
thread is alive before waiting for it to become blocked on the
conditional variable.
* src/thread.c (lisp_mutex_lock, lisp_mutex_unlock)
(lisp_mutex_unlock_for_wait, condition_wait_callback)
(condition_notify_callback): Improve commentary.
(condition_wait_callback): Call post_acquire_global_lock before
attempting to lock the mutex, to make sure the lock's owner is
recorded correctly.
* test/src/thread-tests.el (threads-condvar-wait): New test.
* src/thread.c (post_acquire_global_lock): Don't raise the pending
signal if the thread's handlers were not yet set up, as that will
cause Emacs to exit with a fatal error. This can happen if a
thread is signaled as soon as make-thread returns, before the new
thread had an opportunity to acquire the global lock, set up the
handlers, and call the thread function.
* test/src/thread-tests.el (thread-signal-early): New test.
* src/thread.c (post_acquire_global_lock): Call
set_buffer_internal_2 instead of tricking set_buffer_internal_1
into resetting the current buffer even if it didn't change. This
avoids bug#25165, caused by failing to record the modified values
of point and mark, because current_buffer was set to NULL. Also,
don't bother re-setting the buffer if there was no thread switch,
as that just wastes cycles.
* src/buffer.c (set_buffer_internal_2): New function, with most of
the body of set_buffer_internal_1, but without the test for B
being identical to the current buffer.
(set_buffer_internal_1): Call set_buffer_internal_2 if B is not
identical to the current buffer.
* src/buffer.h (set_buffer_internal_2): Add prototype.
* test/src/thread-tests.el (thread-sticky-point): New test.
* src/thread.h (struct thread_state): Add members
m_waiting_for_input and m_input_available_clear_time.
(waiting_for_input, input_available_clear_time): New macros.
* src/keyboard.c (waiting_for_input, input_available_clear_time):
Remove; they are now macros that reference the current thread.
(Bug#25171)
* src/w32select.c: Don't include keyboard.h.
* test/src/thread-tests.el (thread-errors): New test.
