[Emacs-diffs] master 644f77b: Avoid assertion violations when using marker positions

[Eli Zaretskii]

branch: master
commit 644f77b517180c5f75a9eaac4d76b12a1f334ce6
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    Avoid assertion violations when using marker positions
    
    * src/intervals.c (set_point_from_marker): If MARKER comes from
    another buffer, recalculate its byte position before using it to
    set point.
    * src/marker.c (set_marker_internal): If POSITION is a marker from
    another buffer, recalculate its byte position before using it.
    (Bug#24368)
---
 src/intervals.c |   13 +++++++++----
 src/marker.c    |    6 +++++-
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/intervals.c b/src/intervals.c
index 8451069..e797e25 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -1821,11 +1821,16 @@ set_point (ptrdiff_t charpos)
 void
 set_point_from_marker (Lisp_Object marker)
 {
+  ptrdiff_t charpos = clip_to_bounds (BEGV, marker_position (marker), ZV);
+  ptrdiff_t bytepos = marker_byte_position (marker);
+
+  /* Don't trust the byte position if the marker belongs to a
+     different buffer.  */
   if (XMARKER (marker)->buffer != current_buffer)
-    signal_error ("Marker points into wrong buffer", marker);
-  set_point_both
-    (clip_to_bounds (BEGV, marker_position (marker), ZV),
-     clip_to_bounds (BEGV_BYTE, marker_byte_position (marker), ZV_BYTE));
+    bytepos = buf_charpos_to_bytepos (current_buffer, charpos);
+  else
+    bytepos = clip_to_bounds (BEGV_BYTE, bytepos, ZV_BYTE);
+  set_point_both (charpos, bytepos);
 }
 
 /* If there's an invisible character at position POS + TEST_OFFS in the
diff --git a/src/marker.c b/src/marker.c
index febdb17..05e5bb8 100644
--- a/src/marker.c
+++ b/src/marker.c
@@ -507,7 +507,11 @@ set_marker_internal (Lisp_Object marker, Lisp_Object 
position,
       charpos = clip_to_bounds
        (restricted ? BUF_BEGV (b) : BUF_BEG (b), charpos,
         restricted ? BUF_ZV (b) : BUF_Z (b));
-      if (bytepos == -1)
+      /* Don't believe BYTEPOS if it comes from a different buffer,
+        since that buffer might have a very different correspondence
+        between character and byte positions.  */
+      if (bytepos == -1
+         || !(MARKERP (position) && XMARKER (position)->buffer == b))
        bytepos = buf_charpos_to_bytepos (b, charpos);
       else
        bytepos = clip_to_bounds