bug#59794: 29.0.60; NSport segfaults when a fullscreen frame is being closed)

[Kai Ma <justksqsf@gmail.com>]

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> On Dec 4, 2022, at 20:21, Eli Zaretskii <eliz@gnu.org> wrote:
>> Thanks.  I'm fine with installing this on the release branch, but the
>> comment should be modified to say:
>> 
>>  [resetCursorRects:] can be called from the event loop after the frame
>>  is deleted.  When this happens, emacsframe is NULL.  This means there
>>  is an underlying leak of the EmacsView object!
>> 
>> also, perhaps it should be omitted on master, at least until before
>> Emacs 30 is released, to motivate other (hopefully more knowledgeable)
>> people to provide the necessary information to fix it.
> 
> Will do, thanks.


I took a few liberties here.  Attached is the revised patch.


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From 3ea07d5375671b052b717c0523f3e145ef7cc5a2 Mon Sep 17 00:00:00 2001
From: Kai Ma <justksqsf@gmail.com>
Date: Sat, 3 Dec 2022 18:17:26 +0800
Subject: [PATCH] Prevent a segfault when deleting a fullscreen frame on
 NextStep.

* nsterm.m ([EmacsView resetCursorRects:]): Be defensive when
accessing FRAME_OUTPUT_DATA.
---
 src/nsterm.m | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/nsterm.m b/src/nsterm.m
index 507f2a9e7d..f99d7cde3c 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -6703,8 +6703,18 @@ - (BOOL)acceptsFirstResponder
 
 - (void)resetCursorRects
 {
-  NSRect visible = [self visibleRect];
-  NSCursor *currentCursor = FRAME_POINTER_TYPE (emacsframe);
+  NSRect visible;
+  NSCursor *currentCursor;
+
+  /* FIXME: [resetCursorRects:] can be called from the event loop
+     after the frame is deleted.  When this happens,
+     emacsframe->output_data is NULL.  This means there is an
+     underlying leak of the EmacsView object!  (bug#59794) */
+  if (! emacsframe || ! FRAME_OUTPUT_DATA (emacsframe))
+    return;
+
+  visible = [self visibleRect];
+  currentCursor = FRAME_POINTER_TYPE (emacsframe);
   NSTRACE ("[EmacsView resetCursorRects]");
 
   if (currentCursor == nil)
-- 
2.37.1 (Apple Git-137.1)


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