Injecting more "const" declarations into code which does not change

pointed data.
I ran gcc -Wcast-qual on storage/maria, this identified un-needed casts,
a couple of functions which said they had a const parameter though
they changed the pointed content! This is fixed here. Some suspicious
places receive a comment.
The original intention of running -Wcast-qual was to find what code
changes R-tree keys: I added const words, but hidden casts
like those of int2store (casts target to (uint16*)) removed const
checking; -Wcast-qual helped find those hidden casts.
Log handler does not change the content pointed by LEX_STRING::str it
receives, so we now use a struct which has a const inside, to emphasize
this and be able to pass "const uchar*" buffers to log handler
without fear of their content being changed by it.
One-line fix for a merge glitch (when merging from MyISAM).


include/m_string.h:
  As Maria's log handler uses LEX_STRING but never changes the content
  pointed by LEX_STRING::str, and assigns uchar* into this member most
  of the time, we introduce a new struct LEX_CUSTRING
  (C const U unsigned) for the log handler.
include/my_global.h:
  In macros which read pointed content: use const pointers so that
  gcc -Wcast-qual does not warn about casting a const pointer to non-const.
include/my_handler.h:
  In macros which read pointed content: use const pointers so that
  gcc -Wcast-qual does not warn about casting a const pointer to non-const.
  ha_find_null() does not change *a.
include/my_sys.h:
  insert_dynamic() does not change *element.
include/myisampack.h:
  In macros which read pointed content: use const pointers so that
  gcc -Wcast-qual does not warn about casting a const pointer to non-const.
mysys/array.c:
  insert_dynamic() does not change *element
mysys/my_handler.c:
  ha_find_null() does not change *a
storage/maria/ma_bitmap.c:
  Log handler receives const strings now
storage/maria/ma_blockrec.c:
  Log handler receives const strings now.
  _ma_apply_undo_row_delete/update() do change *header.
storage/maria/ma_blockrec.h:
  correct prototype
storage/maria/ma_check.c:
  Log handler receives const strings now. Un-needed casts
storage/maria/ma_checkpoint.c:
  Log handler receives const strings now
storage/maria/ma_checksum.c:
  unneeded cast
storage/maria/ma_commit.c:
  Log handler receives const strings now
storage/maria/ma_create.c:
  Log handler receives const strings now
storage/maria/ma_dbug.c:
  fixing warning of gcc -Wcast-qual
storage/maria/ma_delete.c:
  Log handler receives const strings now
storage/maria/ma_delete_all.c:
  Log handler receives const strings now
storage/maria/ma_delete_table.c:
  Log handler receives const strings now
storage/maria/ma_dynrec.c:
  fixing some warnings of gcc -Wcast-qual. Unneeded casts removed.
  Comment about function which lies.
storage/maria/ma_ft_parser.c:
  fix for warnings of gcc -Wcast-qual, removing unneeded casts
storage/maria/ma_ft_update.c:
  less casts, comment
storage/maria/ma_key.c:
  less casts, stay const (warnings of gcc -Wcast-qual)
storage/maria/ma_key_recover.c:
  Log handler receives const strings now
storage/maria/ma_loghandler.c:
  Log handler receives const strings now
storage/maria/ma_loghandler.h:
  Log handler receives const strings now
storage/maria/ma_loghandler_lsn.h:
  In macros which read pointed content: use const pointers so that
  gcc -Wcast-qual does not warn about casting a const pointer to non-const.
storage/maria/ma_page.c:
  Log handler receives const strings now; more const
storage/maria/ma_recovery.c:
  Log handler receives const strings now
storage/maria/ma_rename.c:
  Log handler receives const strings now
storage/maria/ma_rt_index.c:
  more const, to emphasize that functions don't change pointed content.
  best_key= NULL was forgotten during merge from MyISAM a few days ago,
  was causing a Valgrind warning
storage/maria/ma_rt_index.h:
  new proto
storage/maria/ma_rt_key.c:
  more const
storage/maria/ma_rt_key.h:
  new proto
storage/maria/ma_rt_mbr.c:
  more const for functions which deserve it
storage/maria/ma_rt_mbr.h:
  new prototype
storage/maria/ma_rt_split.c:
  make const what is not changed.
storage/maria/ma_search.c:
  un-needed casts, more const
storage/maria/ma_sp_key.c:
  more const
storage/maria/ma_unique.c:
  un-needed casts.
storage/maria/ma_write.c:
  Log handler receives const strings now
storage/maria/maria_def.h:
  some more const
storage/maria/unittest/ma_test_loghandler-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_first_lsn-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_max_lsn-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_multigroup-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_multithread-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_noflush-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_nologs-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_pagecache-t.c:
  Log handler receives const strings now
storage/maria/unittest/ma_test_loghandler_purge-t.c:
  Log handler receives const strings now

1 files changed, 27 insertions, 21 deletions

diff --git a/storage/maria/ma_rt_index.c b/storage/maria/ma_rt_index.c
index fea8b7c2d29..1608900d8f3 100644
--- a/storage/maria/ma_rt_index.c
+++ b/storage/maria/ma_rt_index.c
@@ -455,10 +455,11 @@ int maria_rtree_get_next(MARIA_HA *info, uint keynr, uint key_length)
 */
 
 #ifdef PICK_BY_PERIMETER
-static uchar *maria_rtree_pick_key(MARIA_HA *info, MARIA_KEYDEF *keyinfo,
-                                   uchar *key,
-                                   uint key_length, uchar *page_buf,
-                                   uint nod_flag)
+static const uchar *maria_rtree_pick_key(const MARIA_HA *info,
+                                         const MARIA_KEYDEF *keyinfo,
+                                         const uchar *key,
+                                         uint key_length, const uchar *page_buf,
+                                         uint nod_flag)
 {
   double increase;
   double best_incr;
@@ -491,22 +492,22 @@ static uchar *maria_rtree_pick_key(MARIA_HA *info, MARIA_KEYDEF *keyinfo,
 #endif /*PICK_BY_PERIMETER*/
 
 #ifdef PICK_BY_AREA
-static uchar *maria_rtree_pick_key(MARIA_HA *info, MARIA_KEYDEF *keyinfo,
-                                  uchar *key,
-                                  uint key_length, uchar *page_buf,
-                                  uint nod_flag)
+static const uchar *maria_rtree_pick_key(const MARIA_HA *info,
+                                         const MARIA_KEYDEF *keyinfo,
+                                         const uchar *key,
+                                         uint key_length, const uchar *page_buf,
+                                         uint nod_flag)
 {
   MARIA_SHARE *share= info->s;
   double increase;
   double best_incr= DBL_MAX;
   double area;
   double best_area;
-  uchar *best_key;
-  uchar *k= rt_PAGE_FIRST_KEY(share, page_buf, nod_flag);
-  uchar *last= rt_PAGE_END(share, page_buf);
+  const uchar *best_key= NULL;
+  const uchar *k= rt_PAGE_FIRST_KEY(share, page_buf, nod_flag);
+  const uchar *last= rt_PAGE_END(share, page_buf);
 
   LINT_INIT(best_area);
-  LINT_INIT(best_key);
 
   for (; k < last; k= rt_PAGE_NEXT_KEY(share, k, key_length, nod_flag))
   {
@@ -537,8 +538,9 @@ static uchar *maria_rtree_pick_key(MARIA_HA *info, MARIA_KEYDEF *keyinfo,
     1	Child was split
 */
 
-static int maria_rtree_insert_req(MARIA_HA *info, MARIA_KEYDEF *keyinfo,
-                                  uchar *key,
+static int maria_rtree_insert_req(MARIA_HA *info,
+                                  const MARIA_KEYDEF *keyinfo,
+                                  const uchar *key,
                                   uint key_length, my_off_t page,
                                   my_off_t *new_page,
                                   int ins_level, int level)
@@ -565,9 +567,10 @@ static int maria_rtree_insert_req(MARIA_HA *info, MARIA_KEYDEF *keyinfo,
   if ((ins_level == -1 && nod_flag) ||       /* key: go down to leaf */
       (ins_level > -1 && ins_level > level)) /* branch: go down to ins_level */
   {
-    if ((k= maria_rtree_pick_key(info, keyinfo, key, key_length, page_buf,
-                                  nod_flag)) == NULL)
+    if ((k= (uchar *)maria_rtree_pick_key(info, keyinfo, key, key_length,
+                                          page_buf, nod_flag)) == NULL)
       goto err1;
+    /* k is now a pointer inside the page_buf buffer */
     switch ((res= maria_rtree_insert_req(info, keyinfo, key, key_length,
                                           _ma_kpos(nod_flag, k), new_page,
                                           ins_level, level + 1)))
@@ -639,8 +642,9 @@ err1:
     1	Root was split
 */
 
-static int maria_rtree_insert_level(MARIA_HA *info, uint keynr, uchar *key,
-                                    uint key_length, int ins_level)
+int maria_rtree_insert_level(MARIA_HA *info, uint keynr,
+                             const uchar *key,
+                             uint key_length, int ins_level)
 {
   my_off_t old_root;
   MARIA_SHARE *share= info->s;
@@ -754,7 +758,8 @@ err1:
     0	OK
 */
 
-int maria_rtree_insert(MARIA_HA *info, uint keynr, uchar *key, uint key_length)
+int maria_rtree_insert(MARIA_HA *info, uint keynr,
+                       uchar *key, uint key_length)
 {
   int res;
   DBUG_ENTER("maria_rtree_insert");
@@ -809,7 +814,7 @@ err1:
 */
 
 static int maria_rtree_delete_req(MARIA_HA *info, MARIA_KEYDEF *keyinfo,
-                                  uchar *key,
+                                  const uchar *key,
                                   uint key_length, my_off_t page,
                                   uint *page_size,
                                   stPageList *ReinsertList, int level)
@@ -970,7 +975,8 @@ err1:
     0	Deleted
 */
 
-int maria_rtree_delete(MARIA_HA *info, uint keynr, uchar *key, uint key_length)
+int maria_rtree_delete(MARIA_HA *info, uint keynr,
+                       uchar *key, uint key_length)
 {
   MARIA_SHARE *share= info->s;
   uint page_size;