Attempt to fix bug #17962 with SIGSEGV in display_line.

 src/xdisp.c (display_line): Don't call FETCH_BYTE with argument less than 1.

2 files changed, 7 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 493bcde7418..9051d37fcef 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,8 @@
 2014-07-12  Eli Zaretskii  <eliz@gnu.org>
 
+        * xdisp.c (display_line): Don't call FETCH_BYTE with argument less
+        than 1.  (Bug#17962)
+
         * w32fns.c (Fx_file_dialog): Mention in the doc string the
         behavior on Windows 7 and later when the function is repeatedly
         invoked with the same value of DIR.  (Bug#17950)
diff --git a/src/xdisp.c b/src/xdisp.c
index 61d1fa24c68..6918c4360d4 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -20512,7 +20512,10 @@ display_line (struct it *it)
           row->truncated_on_right_p = 1;
           it->continuation_lines_width = 0;
           reseat_at_next_visible_line_start (it, 0);
-          row->ends_at_zv_p = FETCH_BYTE (IT_BYTEPOS (*it) - 1) != '\n';
+          if (IT_BYTEPOS (*it) <= BEG_BYTE)
+            row->ends_at_zv_p = true;
+          else
+            row->ends_at_zv_p = FETCH_BYTE (IT_BYTEPOS (*it) - 1) != '\n';
           break;
         }
     }