[linemap PATCH] Constify lookup

https://gcc.gnu.org/ml/gcc-patches/2019-10/msg01080.html
looking up a line map takes a non-constant line_maps object, which is confusing.
This makes the caching fields mutable, so permits a constant object, as one might expect for a lookup.

	* include/line-map.h (struct maps_info_ordinary): Make cache
	mutable.
	(struct maps_info_macro): Likewise.
	(LINEMAPS_CACHE): Remove non-ref accessor. Constify ref accessor.
	(LINEMAPS_ORDINARY_CACHE, LINEMAPS_MACRO_CACHE): Likewise.
	(LINEMAPS_ORDINARY_MAP_AT, LINEMAPS_MACRO_MAP_AT): Use
	LINEMAPS_USED and LINEMAPS_MAP_AT.
	(linemap_lookup): Constify line_map arg.
	linemap.c (linemap_ordinary_map_lookup, linemap_macro_map_lookup):
	Constify line_map arg.

From-SVN: r276994

3 files changed, 32 insertions, 46 deletions

diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index e8d2e488588..670e97b039a 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,16 @@
+2019-10-15  Nathan Sidwell  <nathan@acm.org>
+
+	* include/line-map.h (struct maps_info_ordinary): Make cache
+	mutable.
+	(struct maps_info_macro): Likewise.
+	(LINEMAPS_CACHE): Remove non-ref accessor. Constify ref accessor.
+	(LINEMAPS_ORDINARY_CACHE, LINEMAPS_MACRO_CACHE): Likewise.
+	(LINEMAPS_ORDINARY_MAP_AT, LINEMAPS_MACRO_MAP_AT): Use
+	LINEMAPS_USED and LINEMAPS_MAP_AT.
+	(linemap_lookup): Constify line_map arg.
+	linemap.c (linemap_ordinary_map_lookup, linemap_macro_map_lookup):
+	Constify line_map arg.
+
 2019-10-11  Joseph Myers  <joseph@codesourcery.com>
 
 	* include/cpplib.h (struct cpp_options): Add dfp_constants and
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index bde5e533c2b..6f4cf5b9c95 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -724,7 +724,7 @@ struct GTY(()) maps_info_ordinary {
      or equal to ALLOCATED.  */
   unsigned int used;
 
-  unsigned int cache;
+  mutable unsigned int cache;
 };
 
 struct GTY(()) maps_info_macro {
@@ -739,7 +739,7 @@ struct GTY(()) maps_info_macro {
      or equal to ALLOCATED.  */
   unsigned int used;
 
-  unsigned int cache;
+  mutable unsigned int cache;
 };
 
 /* Data structure to associate a source_range together with an arbitrary
@@ -865,19 +865,8 @@ LINEMAPS_USED (line_maps *set, bool map_kind)
 /* Returns the index of the last map that was looked up with
    linemap_lookup. MAP_KIND shall be TRUE if we are interested in
    macro maps, FALSE otherwise.  */
-inline unsigned int
-LINEMAPS_CACHE (const line_maps *set, bool map_kind)
-{
-  if (map_kind)
-    return set->info_macro.cache;
-  else
-    return set->info_ordinary.cache;
-}
-
-/* As above, but by reference (e.g. as an lvalue).  */
-
 inline unsigned int &
-LINEMAPS_CACHE (line_maps *set, bool map_kind)
+LINEMAPS_CACHE (const line_maps *set, bool map_kind)
 {
   if (map_kind)
     return set->info_macro.cache;
@@ -927,9 +916,9 @@ LINEMAPS_ORDINARY_MAPS (const line_maps *set)
 inline line_map_ordinary *
 LINEMAPS_ORDINARY_MAP_AT (const line_maps *set, int index)
 {
-  linemap_assert (index >= 0);
-  linemap_assert ((unsigned int)index < set->info_ordinary.used);
-  return &set->info_ordinary.maps[index];
+  linemap_assert (index >= 0
+		  && (unsigned int)index < LINEMAPS_USED (set, false));
+  return (line_map_ordinary *)LINEMAPS_MAP_AT (set, false, index);
 }
 
 /* Return the number of ordinary maps allocated in the line table
@@ -949,16 +938,8 @@ LINEMAPS_ORDINARY_USED (const line_maps *set)
 
 /* Return the index of the last ordinary map that was looked up with
    linemap_lookup.  */
-inline unsigned int
-LINEMAPS_ORDINARY_CACHE (const line_maps *set)
-{
-  return LINEMAPS_CACHE (set, false);
-}
-
-/* As above, but by reference (e.g. as an lvalue).  */
-
 inline unsigned int &
-LINEMAPS_ORDINARY_CACHE (line_maps *set)
+LINEMAPS_ORDINARY_CACHE (const line_maps *set)
 {
   return LINEMAPS_CACHE (set, false);
 }
@@ -991,9 +972,9 @@ LINEMAPS_MACRO_MAPS (const line_maps *set)
 inline line_map_macro *
 LINEMAPS_MACRO_MAP_AT (const line_maps *set, int index)
 {
-  linemap_assert (index >= 0);
-  linemap_assert ((unsigned int)index < set->info_macro.used);
-  return &set->info_macro.maps[index];
+  linemap_assert (index >= 0
+		  && (unsigned int)index < LINEMAPS_USED (set, true));
+  return (line_map_macro *)LINEMAPS_MAP_AT (set, true, index);
 }
 
 /* Returns the number of macro maps that were allocated in the line
@@ -1011,18 +992,10 @@ LINEMAPS_MACRO_USED (const line_maps *set)
   return LINEMAPS_USED (set, true);
 }
 
-/* Returns the index of the last macro map looked up with
+/* Return the index of the last macro map that was looked up with
    linemap_lookup.  */
-inline unsigned int
-LINEMAPS_MACRO_CACHE (const line_maps *set)
-{
-  return LINEMAPS_CACHE (set, true);
-}
-
-/* As above, but by reference (e.g. as an lvalue).  */
-
 inline unsigned int &
-LINEMAPS_MACRO_CACHE (line_maps *set)
+LINEMAPS_MACRO_CACHE (const line_maps *set)
 {
   return LINEMAPS_CACHE (set, true);
 }
@@ -1130,7 +1103,7 @@ extern const line_map *linemap_add
    binary search. If no line map have been allocated yet, this
    function returns NULL.  */
 extern const line_map *linemap_lookup
-  (class line_maps *, location_t);
+  (const line_maps *, location_t);
 
 /* Returns TRUE if the line table set tracks token locations across
    macro expansion, FALSE otherwise.  */
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index feeb7480876..b86a116bfdd 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -27,9 +27,9 @@ along with this program; see the file COPYING3.  If not see
 #include "hashtab.h"
 
 static void trace_include (const line_maps *, const line_map_ordinary *);
-static const line_map_ordinary * linemap_ordinary_map_lookup (line_maps *,
+static const line_map_ordinary * linemap_ordinary_map_lookup (const line_maps *,
 							      location_t);
-static const line_map_macro* linemap_macro_map_lookup (line_maps *,
+static const line_map_macro* linemap_macro_map_lookup (const line_maps *,
 						       location_t);
 static location_t linemap_macro_map_loc_to_def_point
 (const line_map_macro *, location_t);
@@ -937,7 +937,7 @@ linemap_position_for_loc_and_offset (line_maps *set,
    ordinary or a macro map), returns that map.  */
 
 const struct line_map*
-linemap_lookup (line_maps *set, location_t line)
+linemap_lookup (const line_maps *set, location_t line)
 {
   if (IS_ADHOC_LOC (line))
     line = get_location_from_adhoc_loc (set, line);
@@ -952,7 +952,7 @@ linemap_lookup (line_maps *set, location_t line)
    binary search.  */
 
 static const line_map_ordinary *
-linemap_ordinary_map_lookup (line_maps *set, location_t line)
+linemap_ordinary_map_lookup (const line_maps *set, location_t line)
 {
   unsigned int md, mn, mx;
   const line_map_ordinary *cached, *result;
@@ -965,7 +965,7 @@ linemap_ordinary_map_lookup (line_maps *set, location_t line)
 
   mn = LINEMAPS_ORDINARY_CACHE (set);
   mx = LINEMAPS_ORDINARY_USED (set);
-  
+
   cached = LINEMAPS_ORDINARY_MAP_AT (set, mn);
   /* We should get a segfault if no line_maps have been added yet.  */
   if (line >= MAP_START_LOCATION (cached))
@@ -1000,7 +1000,7 @@ linemap_ordinary_map_lookup (line_maps *set, location_t line)
    binary search.  */
 
 static const line_map_macro *
-linemap_macro_map_lookup (line_maps *set, location_t line)
+linemap_macro_map_lookup (const line_maps *set, location_t line)
 {
   unsigned int md, mn, mx;
   const struct line_map_macro *cached, *result;