if no xa recovery (or after it):

  warning on startup if prepared foreign xids
  error on startup if prepared our xids
  temporarily: always rollback prepared our xids instead of an error


sql/mysql_priv.h:
  opt_tc_log_file made extern
sql/mysqld.cc:
  opt_tc_log_file made extern
  always call ha_recover() even if no previous crash was detected

sql/handler.cc

@@ -744,16 +744,48 @@ int ha_commit_or_rollback_by_xid(LEX_STRING *ident, bool commit)
 
 /*
   recover() step of xa
+
+  NOTE
+   there are three modes of operation:
+
+   - automatic recover after a crash
+     in this case commit_list != 0, tc_heuristic_recover==0
+     all xids from commit_list are committed, others are rolled back
+
+   - manual (heuristic) recover
+     in this case commit_list==0, tc_heuristic_recover != 0
+     DBA has explicitly specified that all prepared transactions should
+     be committed (or rolled back).
+
+   - no recovery (MySQL did not detect a crash)
+     in this case commit_list==0, tc_heuristic_recover == 0
+     there should be no prepared transactions in this case.
 */
 int ha_recover(HASH *commit_list)
 {
-  int len, got;
+  int len, got, found_foreign_xids=0, found_my_xids=0;
   handlerton **ht= handlertons, **end_ht=ht+total_ha;
   XID *list=0;
+  bool dry_run=(commit_list==0 && tc_heuristic_recover==0);
   DBUG_ENTER("ha_recover");
 
-  DBUG_ASSERT(total_ha_2pc);
-  DBUG_ASSERT(commit_list || tc_heuristic_recover);
+  /* commit_list and tc_heuristic_recover cannot be set both */
+  DBUG_ASSERT(commit_list==0 || tc_heuristic_recover==0);
+  /* if either is set, total_ha_2pc must be set too */
+  DBUG_ASSERT((commit_list==0 && tc_heuristic_recover==0) || total_ha_2pc>0);
+
+  if (total_ha_2pc == 0)
+    DBUG_RETURN(0);
+
+#ifndef WILL_BE_DELETED_LATER
+  /*
+    for now, only InnoDB supports 2pc. It means we can always safely
+    rollback all pending transactions, without risking inconsistent data
+  */
+  DBUG_ASSERT(total_ha_2pc == opt_bin_log+1); // only InnoDB and binlog
+  tc_heuristic_recover= TC_HEURISTIC_RECOVER_ROLLBACK; // forcing ROLLBACK
+  dry_run=FALSE;
+#endif
 
   for (len= MAX_XID_LIST_SIZE ; list==0 && len > MIN_XID_LIST_SIZE; len/=2)
   {
@@ -761,7 +793,7 @@ int ha_recover(HASH *commit_list)
   }
   if (!list)
   {
-    my_error(ER_OUTOFMEMORY, MYF(0), len);
+    sql_print_error(ER(ER_OUTOFMEMORY), len*sizeof(XID));
     DBUG_RETURN(1);
   }
 
@@ -775,7 +807,16 @@ int ha_recover(HASH *commit_list)
       {
         my_xid x=list[i].get_my_xid();
         if (!x) // not "mine" - that is generated by external TM
+        {
+          found_foreign_xids++;
+          continue;
+        }
+        if (dry_run)
+        {
+          found_my_xids++;
           continue;
+        }
+        // recovery mode
         if (commit_list ?
             hash_search(commit_list, (byte *)&x, sizeof(x)) != 0 :
             tc_heuristic_recover == TC_HEURISTIC_RECOVER_COMMIT)
@@ -788,6 +829,19 @@ int ha_recover(HASH *commit_list)
     }
   }
   my_free((gptr)list, MYF(0));
+  if (found_foreign_xids)
+    sql_print_warning("Found %d prepared XA transactions", found_foreign_xids);
+  if (dry_run && found_my_xids)
+  {
+    sql_print_error("Found %d prepared transactions! It means that mysqld was "
+                    "not shut down properly last time and critical recovery "
+                    "information (last binlog or %s file) was manually deleted "
+                    "after a crash. You have to start mysqld with "
+                    "--tc-heuristic-recover switch to commit or rollback "
+                    "pending transactions.",
+                    found_my_xids, opt_tc_log_file);
+    DBUG_RETURN(1);
+  }
   DBUG_RETURN(0);
 }
 
@@ -1385,7 +1439,7 @@ ulonglong handler::get_auto_increment()
 /*
   Print error that we got from handler function
 
-  NOTE:
+  NOTE
    In case of delete table it's only safe to use the following parts of
    the 'table' structure:
      table->s->path

sql/mysql_priv.h

@@ -1033,7 +1033,7 @@ extern Le_creator le_creator;
 extern char language[FN_REFLEN], reg_ext[FN_EXTLEN];
 extern char glob_hostname[FN_REFLEN], mysql_home[FN_REFLEN];
 extern char pidfile_name[FN_REFLEN], system_time_zone[30], *opt_init_file;
-extern char log_error_file[FN_REFLEN];
+extern char log_error_file[FN_REFLEN], *opt_tc_log_file;
 extern double last_query_cost;
 extern double log_10[32];
 extern ulonglong log_10_int[20];

sql/mysqld.cc

@@ -366,7 +366,7 @@ char* log_error_file_ptr= log_error_file;
 char mysql_real_data_home[FN_REFLEN],
      language[FN_REFLEN], reg_ext[FN_EXTLEN], mysql_charsets_dir[FN_REFLEN],
      *mysqld_user,*mysqld_chroot, *opt_init_file,
-     *opt_init_connect, *opt_init_slave,
+     *opt_init_connect, *opt_init_slave, *opt_tc_log_file,
      def_ft_boolean_syntax[sizeof(ft_boolean_syntax)];
 
 const char *opt_date_time_formats[3];
@@ -457,7 +457,7 @@ static my_bool opt_do_pstack, opt_noacl, opt_bootstrap, opt_myisam_log;
 static int cleanup_done;
 static ulong opt_specialflag, opt_myisam_block_size;
 static char *opt_logname, *opt_update_logname, *opt_binlog_index_name;
-static char *opt_slow_logname, *opt_tc_log_file, *opt_tc_heuristic_recover;
+static char *opt_slow_logname, *opt_tc_heuristic_recover;
 static char *mysql_home_ptr, *pidfile_name_ptr;
 static char **defaults_argv;
 static char *opt_bin_logname;
@@ -2800,6 +2800,11 @@ server.");
     unireg_abort(1);
   }
 
+  if (ha_recover(0))
+  {
+    unireg_abort(1);
+  }
+
   if (opt_bin_log && mysql_bin_log.open(opt_bin_logname, LOG_BIN, 0,
                                         WRITE_CACHE, 0, max_binlog_size, 0))
       unireg_abort(1);