Avoid crashes upon C-g in nested invocations of 'read_char'

* src/keyboard.c (read_char, read_event_from_main_queue):
Ensure the global value of getcjmp is restored when the stack
is unwound by the likes of 'throw', by calling
record_unwind_protect_ptr instead of restoring the value
manually.  (Bug#34394)
(restore_getcjmp): Argument is now 'void *', to match the
signature of record_unwind_protect_ptr.

1 files changed, 11 insertions, 5 deletions

diff --git a/src/keyboard.c b/src/keyboard.c
index cd1747ea88c..1d67c3eaabd 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -360,7 +360,7 @@ static Lisp_Object make_lispy_focus_in (Lisp_Object);
 static Lisp_Object make_lispy_focus_out (Lisp_Object);
 static bool help_char_p (Lisp_Object);
 static void save_getcjmp (sys_jmp_buf);
-static void restore_getcjmp (sys_jmp_buf);
+static void restore_getcjmp (void *);
 static Lisp_Object apply_modifiers (int, Lisp_Object);
 static void restore_kboard_configuration (int);
 static void handle_interrupt (bool);
@@ -2126,12 +2126,14 @@ read_event_from_main_queue (struct timespec *end_time,
     return c;
 
   /* Actually read a character, waiting if necessary.  */
+  ptrdiff_t count = SPECPDL_INDEX ();
   save_getcjmp (save_jump);
+  record_unwind_protect_ptr (restore_getcjmp, save_jump);
   restore_getcjmp (local_getcjmp);
   if (!end_time)
     timer_start_idle ();
   c = kbd_buffer_get_event (&kb, used_mouse_menu, end_time);
-  restore_getcjmp (save_jump);
+  unbind_to (count, Qnil);
 
   if (! NILP (c) && (kb != current_kboard))
     {
@@ -2620,10 +2622,12 @@ read_char (int commandflag, Lisp_Object map,
         {
           Lisp_Object tem0;
 
+          ptrdiff_t count = SPECPDL_INDEX ();
           save_getcjmp (save_jump);
+          record_unwind_protect_ptr (restore_getcjmp, save_jump);
           restore_getcjmp (local_getcjmp);
           tem0 = sit_for (Vecho_keystrokes, 1, 1);
-          restore_getcjmp (save_jump);
+          unbind_to (count, Qnil);
           if (EQ (tem0, Qt)
               && ! CONSP (Vunread_command_events))
             echo_now ();
@@ -2694,10 +2698,12 @@ read_char (int commandflag, Lisp_Object map,
 
           timeout = min (timeout, MOST_POSITIVE_FIXNUM / delay_level * 4);
           timeout = delay_level * timeout / 4;
+          ptrdiff_t count1 = SPECPDL_INDEX ();
           save_getcjmp (save_jump);
+          record_unwind_protect_ptr (restore_getcjmp, save_jump);
           restore_getcjmp (local_getcjmp);
           tem0 = sit_for (make_fixnum (timeout), 1, 1);
-          restore_getcjmp (save_jump);
+          unbind_to (count1, Qnil);
 
           if (EQ (tem0, Qt)
               && ! CONSP (Vunread_command_events))
@@ -3320,7 +3326,7 @@ save_getcjmp (sys_jmp_buf temp)
 }
 
 static void
-restore_getcjmp (sys_jmp_buf temp)
+restore_getcjmp (void *temp)
 {
   memcpy (getcjmp, temp, sizeof getcjmp);
 }