Add variable main-thread, fix Bug#32169

* doc/lispref/threads.texi (Basic Thread Functions): Add example,
how to propagate signals to the main thread.  Describe variable
`main-thread'.  Document optional argument CLEANUP of
`thread-last-error'.

* src/thread.c (Fthread_last_error): Add optional argument
CLEANUP.  (Bug#32169)
(main-thread): New defvar.

* test/src/thread-tests.el (thread-last-error): Adapt declaration.
(main-thread): Declare.
(threads-main-thread): New test.
(threads-errors): Extend test.

1 files changed, 10 insertions, 1 deletions

diff --git a/test/src/thread-tests.el b/test/src/thread-tests.el
index a00a9c84bd6..a447fb3914e 100644
--- a/test/src/thread-tests.el
+++ b/test/src/thread-tests.el
@@ -34,10 +34,11 @@
 (declare-function thread--blocker "thread.c" (thread))
 (declare-function thread-alive-p "thread.c" (thread))
 (declare-function thread-join "thread.c" (thread))
-(declare-function thread-last-error "thread.c" ())
+(declare-function thread-last-error "thread.c" (&optional cleanup))
 (declare-function thread-name "thread.c" (thread))
 (declare-function thread-signal "thread.c" (thread error-symbol data))
 (declare-function thread-yield "thread.c" ())
+(defvar main-thread)
 
 (ert-deftest threads-is-one ()
   "Test for existence of a thread."
@@ -71,6 +72,11 @@
   (skip-unless (featurep 'threads))
   (should (listp (all-threads))))
 
+(ert-deftest threads-main-thread ()
+  "Simple test for all-threads."
+  (skip-unless (featurep 'threads))
+  (should (eq main-thread (car (all-threads)))))
+
 (defvar threads-test-global nil)
 
 (defun threads-test-thread1 ()
@@ -275,6 +281,9 @@
       (thread-yield))
     (should (equal (thread-last-error)
                    '(error "Error is called")))
+    (should (equal (thread-last-error 'cleanup)
+                   '(error "Error is called")))
+    (should-not (thread-last-error))
     (setq th2 (make-thread #'threads-custom "threads-custom"))
     (should (threadp th2))))