Make sure buffer is live before retrieving underline properties (Bug#38038)

* src/window.h (WINDOW_BUFFER_LOCAL_VALUE): New macro.
* src/nsterm.m (ns_draw_text_decoration):
* src/w32term.c (w32_draw_glyph_string):
* src/xterm.c (x_draw_glyph_string): Make sure buffer is live
before retrieving underline properties from it (Bug#38038).

4 files changed, 41 insertions, 29 deletions

diff --git a/src/nsterm.m b/src/nsterm.m
index 9d5082b71df..e1d745e332d 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -3435,19 +3435,22 @@ ns_draw_text_decoration (struct glyph_string *s, struct face *face,
               unsigned long descent = s->y + s->height - s->ybase;
               unsigned long minimum_offset;
               BOOL underline_at_descent_line, use_underline_position_properties;
-              Lisp_Object val = buffer_local_value (Qunderline_minimum_offset,
-                                                    s->w->contents);
-              if (FIXNUMP (val))
-                minimum_offset = XFIXNAT (val);
-              else
-                minimum_offset = 1;
-              val = buffer_local_value (Qx_underline_at_descent_line,
-                                        s->w->contents);
-              underline_at_descent_line = !(NILP (val) || EQ (val, Qunbound));
-              val = buffer_local_value (Qx_use_underline_position_properties,
-                                        s->w->contents);
-              use_underline_position_properties =
-                !(NILP (val) || EQ (val, Qunbound));
+              Lisp_Object val = (WINDOW_BUFFER_LOCAL_VALUE
+                                 (Qunderline_minimum_offset, s->w));
+
+              if (FIXNUMP (val))
+                minimum_offset = XFIXNAT (val);
+              else
+                minimum_offset = 1;
+
+              val = (WINDOW_BUFFER_LOCAL_VALUE
+                     (Qx_underline_at_descent_line, s->w));
+              underline_at_descent_line = !(NILP (val) || EQ (val, Qunbound));
+
+              val = (WINDOW_BUFFER_LOCAL_VALUE
+                     (Qx_use_underline_position_properties, s->w));
+              use_underline_position_properties
+                = !(NILP (val) || EQ (val, Qunbound));
 
               /* Use underline thickness of font, defaulting to 1.  */
               thickness = (font && font->underline_thickness > 0)
diff --git a/src/w32term.c b/src/w32term.c
index 9da0845836a..d0537c67e9a 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -2512,20 +2512,21 @@ w32_draw_glyph_string (struct glyph_string *s)
                   unsigned long minimum_offset;
                   BOOL underline_at_descent_line;
                   BOOL use_underline_position_properties;
-                  Lisp_Object val
-                    = buffer_local_value (Qunderline_minimum_offset,
-                                          s->w->contents);
+                  Lisp_Object val = (WINDOW_BUFFER_LOCAL_VALUE
+                                     (Qunderline_minimum_offset, s->w));
+
                   if (FIXNUMP (val))
                     minimum_offset = max (0, XFIXNUM (val));
                   else
                     minimum_offset = 1;
-                  val = buffer_local_value (Qx_underline_at_descent_line,
-                                            s->w->contents);
+
+                  val = (WINDOW_BUFFER_LOCAL_VALUE
+                         (Qx_underline_at_descent_line, s->w));
                   underline_at_descent_line
                     = !(NILP (val) || EQ (val, Qunbound));
-                  val
-                    = buffer_local_value (Qx_use_underline_position_properties,
-                                          s->w->contents);
+
+                  val = (WINDOW_BUFFER_LOCAL_VALUE
+                         (Qx_use_underline_position_properties, s->w));
                   use_underline_position_properties
                     = !(NILP (val) || EQ (val, Qunbound));
 
diff --git a/src/window.h b/src/window.h
index 71946a56955..5b9a3140c8f 100644
--- a/src/window.h
+++ b/src/window.h
@@ -608,6 +608,13 @@ wset_next_buffers (struct window *w, Lisp_Object val)
    ? (W)->contents                              \
    : Qnil)
 
+/* Local value of variable V in window W's buffer.  Nil if W has no
+   buffer.  */
+#define WINDOW_BUFFER_LOCAL_VALUE(V, W)         \
+  (BUFFERP ((W)->contents)                      \
+   ? buffer_local_value(V, (W)->contents)       \
+   : Qnil)
+
 /* Return the canonical column width of the frame of window W.  */
 #define WINDOW_FRAME_COLUMN_WIDTH(W) \
   (FRAME_COLUMN_WIDTH (WINDOW_XFRAME ((W))))
diff --git a/src/xterm.c b/src/xterm.c
index 44fbd27b11a..f7005804f02 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -3847,20 +3847,21 @@ x_draw_glyph_string (struct glyph_string *s)
                   unsigned long minimum_offset;
                   bool underline_at_descent_line;
                   bool use_underline_position_properties;
-                  Lisp_Object val
-                    = buffer_local_value (Qunderline_minimum_offset,
-                                          s->w->contents);
+                  Lisp_Object val = (WINDOW_BUFFER_LOCAL_VALUE
+                                     (Qunderline_minimum_offset, s->w));
+
                   if (FIXNUMP (val))
                     minimum_offset = max (0, XFIXNUM (val));
                   else
                     minimum_offset = 1;
-                  val = buffer_local_value (Qx_underline_at_descent_line,
-                                            s->w->contents);
+
+                  val = (WINDOW_BUFFER_LOCAL_VALUE
+                         (Qx_underline_at_descent_line, s->w));
                   underline_at_descent_line
                     = !(NILP (val) || EQ (val, Qunbound));
-                  val
-                    = buffer_local_value (Qx_use_underline_position_properties,
-                                          s->w->contents);
+
+                  val = (WINDOW_BUFFER_LOCAL_VALUE
+                         (Qx_use_underline_position_properties, s->w));
                   use_underline_position_properties
                     = !(NILP (val) || EQ (val, Qunbound));