Fix set-marker when the position is larger than the largest buffer

* src/marker.c (set_marker_internal): Handle the case where
POSITION is beyond PTRDIFF_MAX, which can happen if Emacs was
built --with-wide-int.  Bug uncovered by the recently added
overlay tests.

1 files changed, 12 insertions, 1 deletions

diff --git a/src/marker.c b/src/marker.c
index 0b2e1bf5c6b..6358bc3bf79 100644
--- a/src/marker.c
+++ b/src/marker.c
@@ -529,7 +529,18 @@ set_marker_internal (Lisp_Object marker, Lisp_Object position,
          don't want to call buf_charpos_to_bytepos if POSITION
          is a marker and so we know the bytepos already.  */
       if (FIXNUMP (position))
-        charpos = XFIXNUM (position), bytepos = -1;
+        {
+#if EMACS_INT_MAX > PTRDIFF_MAX
+          /* A --with-wide-int build.  */
+          EMACS_INT cpos = XFIXNUM (position);
+          if (cpos > PTRDIFF_MAX)
+            cpos = PTRDIFF_MAX;
+          charpos = cpos;
+          bytepos = -1;
+#else
+          charpos = XFIXNUM (position), bytepos = -1;
+#endif
+        }
       else if (MARKERP (position))
         {
           charpos = XMARKER (position)->charpos;