[PATCH 06/10] Disallow using BVAR as an lvalue

[Spencer Baugh]

This is a prerequisite for later changing BVAR into a function call.

buffer.c keeps the ability to directly access struct buffer Lisp
fields; it has to change to using the new local macro BVAR_DIRECT for
this. buffer.c exclusively uses this ability to access the special
struct buffer instances: buffer_local_flags, buffer_local_symbols, and
buffer_defaults. None of those should fall back to looking up
variables in buffer_defaults.
---
 src/buffer.c | 104 ++++++++++++++++++++++++++-------------------------
 src/buffer.h |   2 +-
 2 files changed, 54 insertions(+), 52 deletions(-)

diff --git a/src/buffer.c b/src/buffer.c
index ba03fed3b9..6bcf1ad596 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -89,6 +89,8 @@ struct buffer buffer_local_symbols;
 #define PER_BUFFER_SYMBOL(OFFSET) \
       (*(Lisp_Object *)((OFFSET) + (char *) &buffer_local_symbols))
 
+#define BVAR_DIRECT(buf, field) ((buf)->field ## _)
+
 /* Maximum length of an overlay vector.  */
 #define OVERLAY_COUNT_MAX                                              \
   ((ptrdiff_t) min (MOST_POSITIVE_FIXNUM,                              \
@@ -5183,53 +5185,53 @@ init_buffer_once (void)
   bset_last_selected_window (&buffer_local_flags, make_fixnum (0));
 
   idx = 1;
-  XSETFASTINT (BVAR (&buffer_local_flags, mode_line_format), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, abbrev_mode), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, overwrite_mode), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, case_fold_search), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, auto_fill_function), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, selective_display), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, selective_display_ellipses), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, tab_width), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, truncate_lines), idx);
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, mode_line_format), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, abbrev_mode), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, overwrite_mode), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, case_fold_search), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, auto_fill_function), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, selective_display), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, selective_display_ellipses), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, tab_width), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, truncate_lines), idx);
   /* Make this one a permanent local.  */
   buffer_permanent_local_flags[idx++] = 1;
-  XSETFASTINT (BVAR (&buffer_local_flags, word_wrap), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, ctl_arrow), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, fill_column), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, left_margin), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, abbrev_table), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, display_table), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, syntax_table), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, cache_long_scans), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, category_table), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, bidi_display_reordering), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, bidi_paragraph_direction), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, bidi_paragraph_separate_re), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, bidi_paragraph_start_re), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, buffer_file_coding_system), idx);
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, word_wrap), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, ctl_arrow), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, fill_column), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, left_margin), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, abbrev_table), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, display_table), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, syntax_table), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, cache_long_scans), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, category_table), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, bidi_display_reordering), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, bidi_paragraph_direction), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, bidi_paragraph_separate_re), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, bidi_paragraph_start_re), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, buffer_file_coding_system), 
idx);
   /* Make this one a permanent local.  */
   buffer_permanent_local_flags[idx++] = 1;
-  XSETFASTINT (BVAR (&buffer_local_flags, left_margin_cols), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, right_margin_cols), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, left_fringe_width), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, right_fringe_width), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, fringes_outside_margins), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, scroll_bar_width), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, scroll_bar_height), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, vertical_scroll_bar_type), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, horizontal_scroll_bar_type), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, indicate_empty_lines), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, indicate_buffer_boundaries), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, fringe_indicator_alist), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, fringe_cursor_alist), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, scroll_up_aggressively), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, scroll_down_aggressively), idx); 
++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, header_line_format), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, tab_line_format), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, cursor_type), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, extra_line_spacing), idx); ++idx;
-  XSETFASTINT (BVAR (&buffer_local_flags, cursor_in_non_selected_windows), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, left_margin_cols), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, right_margin_cols), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, left_fringe_width), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, right_fringe_width), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, fringes_outside_margins), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, scroll_bar_width), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, scroll_bar_height), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, vertical_scroll_bar_type), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, horizontal_scroll_bar_type), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, indicate_empty_lines), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, indicate_buffer_boundaries), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, fringe_indicator_alist), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, fringe_cursor_alist), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, scroll_up_aggressively), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, scroll_down_aggressively), 
idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, header_line_format), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, tab_line_format), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, cursor_type), idx); ++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, extra_line_spacing), idx); 
++idx;
+  XSETFASTINT (BVAR_DIRECT (&buffer_local_flags, 
cursor_in_non_selected_windows), idx); ++idx;
 
   /* buffer_local_flags contains no pointers, so it's safe to treat it
      as a blob for pdumper.  */
@@ -5244,9 +5246,9 @@ init_buffer_once (void)
   /* Make sure all markable slots in buffer_defaults
      are initialized reasonably, so mark_buffer won't choke.  */
   reset_buffer (&buffer_defaults);
-  eassert (NILP (BVAR (&buffer_defaults, name)));
+  eassert (NILP (BVAR_DIRECT (&buffer_defaults, name)));
   reset_buffer_local_variables (&buffer_defaults, 1);
-  eassert (NILP (BVAR (&buffer_local_symbols, name)));
+  eassert (NILP (BVAR_DIRECT (&buffer_local_symbols, name)));
   reset_buffer (&buffer_local_symbols);
   reset_buffer_local_variables (&buffer_local_symbols, 1);
   /* Prevent GC from getting confused.  */
@@ -5289,7 +5291,7 @@ init_buffer_once (void)
   set_buffer_overlays_after (&buffer_defaults, NULL);
   buffer_defaults.overlay_center = BEG;
 
-  XSETFASTINT (BVAR (&buffer_defaults, tab_width), 8);
+  XSETFASTINT (BVAR_DIRECT (&buffer_defaults, tab_width), 8);
   bset_truncate_lines (&buffer_defaults, Qnil);
   bset_word_wrap (&buffer_defaults, Qnil);
   bset_ctl_arrow (&buffer_defaults, Qt);
@@ -5303,13 +5305,13 @@ init_buffer_once (void)
 
   bset_enable_multibyte_characters (&buffer_defaults, Qt);
   bset_buffer_file_coding_system (&buffer_defaults, Qnil);
-  XSETFASTINT (BVAR (&buffer_defaults, fill_column), 70);
-  XSETFASTINT (BVAR (&buffer_defaults, left_margin), 0);
+  XSETFASTINT (BVAR_DIRECT (&buffer_defaults, fill_column), 70);
+  XSETFASTINT (BVAR_DIRECT (&buffer_defaults, left_margin), 0);
   bset_cache_long_scans (&buffer_defaults, Qt);
   bset_file_truename (&buffer_defaults, Qnil);
-  XSETFASTINT (BVAR (&buffer_defaults, display_count), 0);
-  XSETFASTINT (BVAR (&buffer_defaults, left_margin_cols), 0);
-  XSETFASTINT (BVAR (&buffer_defaults, right_margin_cols), 0);
+  XSETFASTINT (BVAR_DIRECT (&buffer_defaults, display_count), 0);
+  XSETFASTINT (BVAR_DIRECT (&buffer_defaults, left_margin_cols), 0);
+  XSETFASTINT (BVAR_DIRECT (&buffer_defaults, right_margin_cols), 0);
   bset_left_fringe_width (&buffer_defaults, Qnil);
   bset_right_fringe_width (&buffer_defaults, Qnil);
   bset_fringes_outside_margins (&buffer_defaults, Qnil);
diff --git a/src/buffer.h b/src/buffer.h
index 0b26c56e89..ae2d785aff 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -282,7 +282,7 @@ struct buffer_text
 
 /* Most code should use this macro to access Lisp fields in struct buffer.  */
 
-#define BVAR(buf, field) ((buf)->field ## _)
+#define BVAR(buf, field) ((void)0, (buf)->field ## _)
 
 /* Access a BVAR from buffer_defaults */
 #define BVAR_DEFAULT(field) (buffer_defaults.field ## _)
-- 
2.28.0