Port --enable-gcc-warnings to GCC 6.1

* configure.ac (WERROR_CFLAGS): Omit -Wunused-const-variable=2.
* lib-src/etags.c (LOOKING_AT, LOOKING_AT_NOCASE):
Omit test whether pointer plus a constant equals a null pointer.
* src/alloc.c (compact_small_strings):
Avoid pointer arithmetic on null pointers.
* src/alloc.c (mark_face_cache):
* src/fontset.c (free_realized_fontsets, Fset_fontset_font):
* src/fringe.c (draw_fringe_bitmap_1)
(Fset_fringe_bitmap_face):
* src/macfont.m (macfont_draw):
* src/msdos.c (IT_set_face, IT_clear_screen):
* src/nsfont.m (nsfont_draw):
* src/nsterm.h (FRAME_DEFAULT_FACE):
* src/nsterm.m (ns_draw_window_cursor)
(ns_draw_vertical_window_border, ns_draw_window_divider)
(ns_dumpglyphs_box_or_relief)
(ns_maybe_dumpglyphs_background, ns_dumpglyphs_image)
(ns_dumpglyphs_stretch):
* src/w32term.c (w32_draw_vertical_window_border)
(w32_draw_window_divider, x_set_mouse_face_gc):
* src/xdisp.c (estimate_mode_line_height, init_iterator)
(handle_face_prop, handle_single_display_spec, pop_it)
(CHAR_COMPOSED_P, get_next_display_element)
(next_element_from_display_vector, extend_face_to_end_of_line)
(fill_gstring_glyph_string,BUILD_COMPOSITE_GLYPH_STRING):
* src/xfaces.c (Finternal_merge_in_global_face, Fface_font)
(lookup_named_face):
* src/xterm.c (x_draw_vertical_window_border)
(x_draw_window_divider, x_set_mouse_face_gc):
Prefer FACE_OPT_FROM_ID to FACE_FROM_ID when the result might be null.
* src/xterm.c (try_window_id):
Redo loop to convince GCC 6.1 that it is null pointer safe.
(x_color_cells):
Use eassume as necessary to pacify GCC 6.1.
* src/dispextern.h (FACE_FROM_ID, IMAGE_FROM_ID): Now returns non-null.
(FACE_OPT_FROM_ID, IMAGE_OPT_FROM_ID): New macro, with the old
behavior of the non-_OPT macro, to be used when the result
might be a null pointer.
* src/dispnew.c (buffer_posn_from_coords, marginal_area_string)
[HAVE_WINDOW_SYSTEM]:
* src/intervals.h (INTERVAL_WRITABLE_P):
* src/term.c (turn_off_face):
* src/xdisp.c (get_glyph_face_and_encoding, fill_image_glyph_string)
(produce_image_glyph, produce_xwidget_glyph):
* src/xfaces.c (lookup_named_face):
Remove unnecessary test for null pointer.
* src/keyboard.c (read_char): Suppress bogus -Wclobbered warning.
* src/process.c (would_block): New function.
(server_accept_connection, wait_reading_process_output, send_process):
Use it.
* src/xdisp.c (get_window_cursor_type, note_mouse_highlight):
Prefer IMAGE_OPT_FROM_ID to IMAGE_FROM_ID when the result
might be null.

1 files changed, 9 insertions, 17 deletions

diff --git a/src/xfaces.c b/src/xfaces.c
index ac1370003df..c42e55333cf 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -3694,7 +3694,7 @@ Default face attributes override any local face attributes.  */)
   if (EQ (face, Qdefault))
     {
       struct face_cache *c = FRAME_FACE_CACHE (f);
-      struct face *newface, *oldface = FACE_FROM_ID (f, DEFAULT_FACE_ID);
+      struct face *newface, *oldface = FACE_OPT_FROM_ID (f, DEFAULT_FACE_ID);
       Lisp_Object attrs[LFACE_VECTOR_SIZE];
 
       /* This can be NULL (e.g., in batch mode).  */
@@ -3777,7 +3777,7 @@ return the font name used for CHARACTER.  */)
     {
       struct frame *f = decode_live_frame (frame);
       int face_id = lookup_named_face (f, face, true);
-      struct face *fface = FACE_FROM_ID (f, face_id);
+      struct face *fface = FACE_OPT_FROM_ID (f, face_id);
 
       if (! fface)
 	return Qnil;
@@ -4429,15 +4429,13 @@ lookup_named_face (struct frame *f, Lisp_Object symbol, bool signal_p)
 {
   Lisp_Object attrs[LFACE_VECTOR_SIZE];
   Lisp_Object symbol_attrs[LFACE_VECTOR_SIZE];
-  struct face *default_face = FACE_FROM_ID (f, DEFAULT_FACE_ID);
+  struct face *default_face = FACE_OPT_FROM_ID (f, DEFAULT_FACE_ID);
 
   if (default_face == NULL)
     {
       if (!realize_basic_faces (f))
 	return -1;
       default_face = FACE_FROM_ID (f, DEFAULT_FACE_ID);
-      if (default_face == NULL)
-	emacs_abort (); /* realize_basic_faces must have set it up  */
     }
 
   if (! get_lface_attributes (f, symbol, symbol_attrs, signal_p, 0))
@@ -4600,9 +4598,6 @@ lookup_derived_face (struct frame *f, Lisp_Object symbol, int face_id,
   Lisp_Object symbol_attrs[LFACE_VECTOR_SIZE];
   struct face *default_face = FACE_FROM_ID (f, face_id);
 
-  if (!default_face)
-    emacs_abort ();
-
   if (!get_lface_attributes (f, symbol, symbol_attrs, signal_p, 0))
     return -1;
 
@@ -4706,7 +4701,7 @@ x_supports_face_attributes_p (struct frame *f,
       merge_face_vectors (f, attrs, merged_attrs, 0);
 
       face_id = lookup_face (f, merged_attrs);
-      face = FACE_FROM_ID (f, face_id);
+      face = FACE_OPT_FROM_ID (f, face_id);
 
       if (! face)
 	error ("Cannot make face");
@@ -4976,14 +4971,12 @@ face for italic.  */)
     attrs[i] = Qunspecified;
   merge_face_ref (f, attributes, attrs, true, 0);
 
-  def_face = FACE_FROM_ID (f, DEFAULT_FACE_ID);
+  def_face = FACE_OPT_FROM_ID (f, DEFAULT_FACE_ID);
   if (def_face == NULL)
     {
       if (! realize_basic_faces (f))
 	error ("Cannot realize default face");
       def_face = FACE_FROM_ID (f, DEFAULT_FACE_ID);
-      if (def_face == NULL)
-	emacs_abort ();  /* realize_basic_faces must have set it up  */
     }
 
   /* Dispatch to the appropriate handler.  */
@@ -5453,7 +5446,7 @@ realize_x_face (struct face_cache *cache, Lisp_Object attrs[LFACE_VECTOR_SIZE])
 
   /* Determine the font to use.  Most of the time, the font will be
      the same as the font of the default face, so try that first.  */
-  default_face = FACE_FROM_ID (f, DEFAULT_FACE_ID);
+  default_face = FACE_OPT_FROM_ID (f, DEFAULT_FACE_ID);
   if (default_face
       && lface_same_font_attributes_p (default_face->lface, attrs))
     {
@@ -6093,7 +6086,6 @@ face_at_string_position (struct window *w, Lisp_Object string,
     *endptr = -1;
 
   base_face = FACE_FROM_ID (f, base_face_id);
-  eassert (base_face);
 
   /* Optimize the default case that there is no face property.  */
   if (NILP (prop)
@@ -6140,7 +6132,7 @@ merge_faces (struct frame *f, Lisp_Object face_name, int face_id,
   Lisp_Object attrs[LFACE_VECTOR_SIZE];
   struct face *base_face;
 
-  base_face = FACE_FROM_ID (f, base_face_id);
+  base_face = FACE_OPT_FROM_ID (f, base_face_id);
   if (!base_face)
     return base_face_id;
 
@@ -6168,7 +6160,7 @@ merge_faces (struct frame *f, Lisp_Object face_name, int face_id,
       struct face *face;
       if (face_id < 0)
 	return base_face_id;
-      face = FACE_FROM_ID (f, face_id);
+      face = FACE_OPT_FROM_ID (f, face_id);
       if (!face)
 	return base_face_id;
       merge_face_vectors (f, face->lface, attrs, 0);
@@ -6288,7 +6280,7 @@ DEFUN ("dump-face", Fdump_face, Sdump_face, 0, 1, 0, doc: /* */)
     {
       struct face *face;
       CHECK_NUMBER (n);
-      face = FACE_FROM_ID (SELECTED_FRAME (), XINT (n));
+      face = FACE_OPT_FROM_ID (SELECTED_FRAME (), XINT (n));
       if (face == NULL)
 	error ("Not a valid face");
       dump_realized_face (face);