From e4deba098e0281538a0e7b04d849989f17e5bcc7 Mon Sep 17 00:00:00 2001
From: Eli Zaretskii <eliz@gnu.org>
Date: Mon, 5 Dec 2016 20:59:11 +0200
Subject: [PATCH] Fix merged code in process.c and eval.c.

---
 src/eval.c    | 31 +++++++++++++++++++++++++------
 src/process.c | 13 ++++++++-----
 2 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/src/eval.c b/src/eval.c
index c08f93aee0c..4405b8bb738 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3323,15 +3323,24 @@ rebind_for_thread_switch (void)
       if (bind->kind >= SPECPDL_LET)
 	{
 	  Lisp_Object value = specpdl_saved_value (bind);
-
+	  Lisp_Object sym = specpdl_symbol (bind);
+	  bool was_trapped =
+	    SYMBOLP (sym)
+	    && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
+	  /* FIXME: This is not clean, and if do_specbind signals an
+	     error, the symbol will be left untrapped.  */
+	  if (was_trapped)
+	    XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
 	  bind->let.saved_value = Qnil;
-	  do_specbind (XSYMBOL (specpdl_symbol (bind)), bind, value);
+	  do_specbind (XSYMBOL (sym, bind, value, true);
+	  if (was_trapped)
+	    XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
 	}
     }
 }
 
 static void
-do_one_unbind (union specbinding *this_binding, int unwinding)
+do_one_unbind (union specbinding *this_binding, bool unwinding)
 {
   eassert (unwinding || this_binding->kind >= SPECPDL_LET);
   switch (this_binding->kind)
@@ -3458,7 +3467,7 @@ unbind_to (ptrdiff_t count, Lisp_Object value)
       union specbinding this_binding;
       this_binding = *--specpdl_ptr;
 
-      do_one_unbind (&this_binding, 1);
+      do_one_unbind (&this_binding, true);
     }
 
   if (NILP (Vquit_flag) && !NILP (quitf))
@@ -3476,8 +3485,18 @@ unbind_for_thread_switch (struct thread_state *thr)
     {
       if ((--bind)->kind >= SPECPDL_LET)
 	{
-	  bind->let.saved_value = find_symbol_value (specpdl_symbol (bind));
-	  do_one_unbind (bind, 0);
+	  Lisp_Object sym = specpdl_symbol (bind);
+	  bool was_trapped =
+	    SYMBOLP (sym)
+	    && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
+	  bind->let.saved_value = find_symbol_value (sym);
+	  /* FIXME: This is not clean, and if do_one_unbind signals an
+	     error, the symbol will be left untrapped.  */
+	  if (was_trapped)
+	    XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
+	  do_one_unbind (bind, false);
+	  if (was_trapped)
+	    XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
 	}
     }
 }
diff --git a/src/process.c b/src/process.c
index e538c86fcf5..7f2a071e67b 100644
--- a/src/process.c
+++ b/src/process.c
@@ -1321,7 +1321,8 @@ See `set-process-sentinel' for more info on sentinels.  */)
 
 DEFUN ("set-process-thread", Fset_process_thread, Sset_process_thread,
        2, 2, 0,
-       doc: /* FIXME */)
+       doc: /* Set the locking thread of PROCESS to be THREAD.
+If THREAD is nil, the process is unlocked.  */)
   (Lisp_Object process, Lisp_Object thread)
 {
   struct Lisp_Process *proc;
@@ -1348,7 +1349,8 @@ DEFUN ("set-process-thread", Fset_process_thread, Sset_process_thread,
 
 DEFUN ("process-thread", Fprocess_thread, Sprocess_thread,
        1, 1, 0,
-       doc: /* FIXME */)
+       doc: /* Ret the locking thread of PROCESS.
+If PROCESS is unlocked, this function returns nil.  */)
   (Lisp_Object process)
 {
   CHECK_PROCESS (process);
@@ -4573,7 +4575,8 @@ is nil, from any process) before the timeout expired.  */)
       /* Can't wait for a process that is dedicated to a different
 	 thread.  */
       if (!EQ (procp->thread, Qnil) && !EQ (procp->thread, Fcurrent_thread ()))
-	error ("FIXME");
+	error ("Attempt to accept output from process %s locked to thread %s",
+	       SDATA (procp->name), SDATA (XTHREAD (procp->thread)->name));
     }
   else
     just_this_one = Qnil;
@@ -5727,7 +5730,7 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
 
 		  if (0 <= p->infd && !EQ (p->filter, Qt)
 		      && !EQ (p->command, Qt))
-		    delete_read_fd (p->infd);
+		    add_read_fd (p->infd);
 		}
 	    }
 	}			/* End for each file descriptor.  */
@@ -7660,7 +7663,7 @@ add_keyboard_wait_descriptor (int desc)
 {
 #ifdef subprocesses /* Actually means "not MSDOS".  */
   eassert (desc >= 0 && desc < FD_SETSIZE);
-  fd_callback_info[desc].flags |= FOR_READ | KEYBOARD_FD;
+  fd_callback_info[desc].flags |= (FOR_READ | KEYBOARD_FD);
   if (desc > max_desc)
     max_desc = desc;
 #endif
-- 
2.39.5