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, 6 insertions, 6 deletions

diff --git a/src/intervals.h b/src/intervals.h
index b8cdcfdc0f5..6a5a4129abc 100644
--- a/src/intervals.h
+++ b/src/intervals.h
@@ -197,12 +197,12 @@ set_interval_plist (INTERVAL i, Lisp_Object plist)
 
 /* Is this interval writable?  Replace later with cache access.  */
 #define INTERVAL_WRITABLE_P(i)					\
-  (i && (NILP (textget ((i)->plist, Qread_only))		\
-         || !NILP (textget ((i)->plist, Qinhibit_read_only))	\
-	 || ((CONSP (Vinhibit_read_only)			\
-	      ? !NILP (Fmemq (textget ((i)->plist, Qread_only),	\
-			      Vinhibit_read_only))		\
-	      : !NILP (Vinhibit_read_only)))))			\
+  (NILP (textget ((i)->plist, Qread_only))			\
+   || !NILP (textget ((i)->plist, Qinhibit_read_only))		\
+   || ((CONSP (Vinhibit_read_only)				\
+	? !NILP (Fmemq (textget ((i)->plist, Qread_only),	\
+			Vinhibit_read_only))			\
+	: !NILP (Vinhibit_read_only))))
 
 /* Macros to tell whether insertions before or after this interval
    should stick to it.  Now we have Vtext_property_default_nonsticky,