[Emacs-diffs] emacs-26 6d89120: Avoid crashes upon C-g in nested invocations of 'read_char'

[Eli Zaretskii]

branch: emacs-26
commit 6d89120b156576ca24e03472563f5ea0f01313f8
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    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.
    
    (cherry picked from commit 10527fca66e39d7067986904161fa33741abcd26)
---
 src/keyboard.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/keyboard.c b/src/keyboard.c
index 49c687f..282eac7 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -364,7 +364,7 @@ static Lisp_Object make_lispy_focus_out (Lisp_Object);
 #endif /* HAVE_WINDOW_SYSTEM */
 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);
@@ -2144,12 +2144,14 @@ 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))
     {
@@ -2638,10 +2640,12 @@ 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 ();
@@ -2712,10 +2716,12 @@ 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_number (timeout), 1, 1);
-         restore_getcjmp (save_jump);
+         unbind_to (count1, Qnil);
 
          if (EQ (tem0, Qt)
              && ! CONSP (Vunread_command_events))
@@ -3325,7 +3331,7 @@ save_getcjmp (sys_jmp_buf temp)
 }
 
 static void
-restore_getcjmp (sys_jmp_buf temp)
+restore_getcjmp (void *temp)
 {
   memcpy (getcjmp, temp, sizeof getcjmp);
 }