diff --git a/cmd-line-utils/readline/bind.c b/cmd-line-utils/readline/bind.c
index fc7bebfd813..2338f73f6c9 100644
--- a/cmd-line-utils/readline/bind.c
+++ b/cmd-line-utils/readline/bind.c
@@ -701,7 +701,7 @@ rl_function_of_keyseq (keyseq, map, type)
     {
       unsigned char ic = keyseq[i];
 
-      if (META_BYTE (ic) && _rl_convert_meta_chars_to_ascii)
+      if (META_CHAR_FOR_UCHAR (ic) && _rl_convert_meta_chars_to_ascii)
 	{
 	  if (map[ESC].type == ISKMAP)
 	    {
diff --git a/cmd-line-utils/readline/chardefs.h b/cmd-line-utils/readline/chardefs.h
index 36fe7fdd7ac..0787d9943bb 100644
--- a/cmd-line-utils/readline/chardefs.h
+++ b/cmd-line-utils/readline/chardefs.h
@@ -59,8 +59,8 @@
 #define largest_char 255		    /* Largest character value. */
 
 #define CTRL_CHAR(c) ((c) < control_character_threshold && (((c) & 0x80) == 0))
-#define META_BYTE(c) ((c) > meta_character_threshold)
-#define META_CHAR(c) (META_BYTE(c) && (c) <= largest_char)
+#define META_CHAR_FOR_UCHAR(c) ((c) > meta_character_threshold)
+#define META_CHAR(c) (META_CHAR_FOR_UCHAR(c) && (c) <= largest_char)
 
 #define CTRL(c) ((c) & control_character_mask)
 #define META(c) ((c) | meta_character_bit)
diff --git a/cmd-line-utils/readline/display.c b/cmd-line-utils/readline/display.c
index 842a586b76b..a68ddff8c88 100644
--- a/cmd-line-utils/readline/display.c
+++ b/cmd-line-utils/readline/display.c
@@ -1888,7 +1888,7 @@ rl_character_len (c, pos)
 
   uc = (unsigned char)c;
 
-  if (META_BYTE (uc))
+  if (META_CHAR_FOR_UCHAR (uc))
     return ((_rl_output_meta_chars == 0) ? 4 : 1);
 
   if (uc == '\t')
diff --git a/mysql-test/r/xa.result b/mysql-test/r/xa.result
index 592cf07522b..92f52b402ec 100644
--- a/mysql-test/r/xa.result
+++ b/mysql-test/r/xa.result
@@ -75,3 +75,9 @@ xa rollback 'a','c';
 xa start 'a','c';
 drop table t1;
 End of 5.0 tests
+xa start 'a';
+xa end 'a';
+xa rollback 'a';
+xa start 'a';
+xa end 'a';
+xa rollback 'a';
diff --git a/mysql-test/t/xa.test b/mysql-test/t/xa.test
index 04ecf518577..a0d5aa60641 100644
--- a/mysql-test/t/xa.test
+++ b/mysql-test/t/xa.test
@@ -124,6 +124,17 @@ drop table t1;
 
 --echo End of 5.0 tests
 
+#
+# Bug#44672: Assertion failed: thd->transaction.xid_state.xid.is_null()
+#
+
+xa start 'a';
+xa end 'a';
+xa rollback 'a';
+xa start 'a';
+xa end 'a';
+xa rollback 'a';
+
 # Wait till all disconnects are completed
 --source include/wait_until_count_sessions.inc
 
diff --git a/sql/handler.cc b/sql/handler.cc
index d22ee220dc1..9246c04ce7d 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -1073,6 +1073,13 @@ int ha_commit_trans(THD *thd, bool all)
     user, or an implicit commit issued by a DDL.
   */
   THD_TRANS *trans= all ? &thd->transaction.all : &thd->transaction.stmt;
+  /*
+    "real" is a nick name for a transaction for which a commit will
+    make persistent changes. E.g. a 'stmt' transaction inside a 'all'
+    transation is not 'real': even though it's possible to commit it,
+    the changes are not durable as they might be rolled back if the
+    enclosing 'all' transaction is rolled back.
+  */
   bool is_real_trans= all || thd->transaction.all.ha_list == 0;
   Ha_trx_info *ha_info= trans->ha_list;
   my_xid xid= thd->transaction.xid_state.xid.get_my_xid();
@@ -1184,16 +1191,9 @@ end:
     if (rw_trans)
       start_waiting_global_read_lock(thd);
   }
-  else if (all)
-  {
-    /*
-      A COMMIT of an empty transaction. There may be savepoints.
-      Destroy them. If the transaction is not empty
-      savepoints are cleared in ha_commit_one_phase()
-      or ha_rollback_trans().
-    */
+  /* Free resources and perform other cleanup even for 'empty' transactions. */
+  else if (is_real_trans)
     thd->transaction.cleanup();
-  }
 #endif /* USING_TRANSACTIONS */
   DBUG_RETURN(error);
 }
@@ -1206,6 +1206,13 @@ int ha_commit_one_phase(THD *thd, bool all)
 {
   int error=0;
   THD_TRANS *trans=all ? &thd->transaction.all : &thd->transaction.stmt;
+  /*
+    "real" is a nick name for a transaction for which a commit will
+    make persistent changes. E.g. a 'stmt' transaction inside a 'all'
+    transation is not 'real': even though it's possible to commit it,
+    the changes are not durable as they might be rolled back if the
+    enclosing 'all' transaction is rolled back.
+  */
   bool is_real_trans=all || thd->transaction.all.ha_list == 0;
   Ha_trx_info *ha_info= trans->ha_list, *ha_info_next;
   DBUG_ENTER("ha_commit_one_phase");
@@ -1227,8 +1234,6 @@ int ha_commit_one_phase(THD *thd, bool all)
     }
     trans->ha_list= 0;
     trans->no_2pc=0;
-    if (is_real_trans)
-      thd->transaction.xid_state.xid.null();
     if (all)
     {
 #ifdef HAVE_QUERY_CACHE
@@ -1236,8 +1241,9 @@ int ha_commit_one_phase(THD *thd, bool all)
         query_cache.invalidate(thd->transaction.changed_tables);
 #endif
       thd->variables.tx_isolation=thd->session_tx_isolation;
-      thd->transaction.cleanup();
     }
+    if (is_real_trans)
+      thd->transaction.cleanup();
   }
 #endif /* USING_TRANSACTIONS */
   DBUG_RETURN(error);
@@ -1249,6 +1255,13 @@ int ha_rollback_trans(THD *thd, bool all)
   int error=0;
   THD_TRANS *trans=all ? &thd->transaction.all : &thd->transaction.stmt;
   Ha_trx_info *ha_info= trans->ha_list, *ha_info_next;
+  /*
+    "real" is a nick name for a transaction for which a commit will
+    make persistent changes. E.g. a 'stmt' transaction inside a 'all'
+    transation is not 'real': even though it's possible to commit it,
+    the changes are not durable as they might be rolled back if the
+    enclosing 'all' transaction is rolled back.
+  */
   bool is_real_trans=all || thd->transaction.all.ha_list == 0;
   DBUG_ENTER("ha_rollback_trans");
 
@@ -1294,18 +1307,13 @@ int ha_rollback_trans(THD *thd, bool all)
     }
     trans->ha_list= 0;
     trans->no_2pc=0;
-    if (is_real_trans)
-    {
-      if (thd->transaction_rollback_request)
-        thd->transaction.xid_state.rm_error= thd->main_da.sql_errno();
-      else
-        thd->transaction.xid_state.xid.null();
-    }
+    if (is_real_trans && thd->transaction_rollback_request)
+      thd->transaction.xid_state.rm_error= thd->main_da.sql_errno();
     if (all)
       thd->variables.tx_isolation=thd->session_tx_isolation;
   }
   /* Always cleanup. Even if there nht==0. There may be savepoints. */
-  if (all)
+  if (is_real_trans)
     thd->transaction.cleanup();
 #endif /* USING_TRANSACTIONS */
   if (all)
diff --git a/sql/sql_class.h b/sql/sql_class.h
index f4d55917b48..ae7f2a51428 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -1464,6 +1464,14 @@ public:
     {
       changed_tables= 0;
       savepoints= 0;
+      /*
+        If rm_error is raised, it means that this piece of a distributed
+        transaction has failed and must be rolled back. But the user must
+        rollback it explicitly, so don't start a new distributed XA until
+        then.
+      */
+      if (!xid_state.rm_error)
+        xid_state.xid.null();
 #ifdef USING_TRANSACTIONS
       free_root(&mem_root,MYF(MY_KEEP_PREALLOC));
 #endif
diff --git a/strings/ctype.c b/strings/ctype.c
index 4a54d898337..17ad1256e74 100644
--- a/strings/ctype.c
+++ b/strings/ctype.c
@@ -328,9 +328,8 @@ my_string_repertoire(CHARSET_INFO *cs, const char *str, ulong length)
   {
     my_wc_t wc;
     int chlen;
-    for (; (chlen= cs->cset->mb_wc(cs, &wc, 
-                                   (const unsigned char *) str, 
-                                   (const unsigned char *) strend)) > 0; 
+    for (;
+         (chlen= cs->cset->mb_wc(cs, &wc, (uchar*) str, (uchar*) strend)) > 0;
          str+= chlen)
     {
       if (wc > 0x7F)