Fix for bug #29420: crash with show and purge binlogs

Problem: in case of failed 'show binlog events...' we don't inform that 
the log is not in use anymore. That may confuse following 'purge logs...'
command as it takes into account logs in use.

Fix: always notify that the log is not in use anymore.


mysql-test/r/rpl_rotate_logs.result:
  Fix for bug #29420: crash with show and purge binlogs
    - test result.
mysql-test/t/rpl_rotate_logs.test:
  Fix for bug #29420: crash with show and purge binlogs
    - test case.
sql/sql_repl.cc:
  Fix for bug #29420: crash with show and purge binlogs
    - always zero thd->current_linfo at the end of the mysql_show_binlog_events().

mysql-test/r/rpl_rotate_logs.result

@@ -95,3 +95,11 @@ count(*)
 100
 unlock tables;
 drop table if exists t1,t2,t3,t4;
+End of 4.1 tests
+show binlog events in 'non existing_binlog_file';
+ERROR HY000: Error when executing command SHOW BINLOG EVENTS: Could not find target log
+purge master logs before now();
+show binlog events in '';
+ERROR HY000: Error when executing command SHOW BINLOG EVENTS: Could not find target log
+purge master logs before now();
+End of 5.0 tests

mysql-test/t/rpl_rotate_logs.test

@@ -169,4 +169,16 @@ connection master;
 drop table if exists t1,t2,t3,t4;
 sync_slave_with_master;
 
-# End of 4.1 tests
+--echo End of 4.1 tests
+
+#
+# Bug #29420: crash with show and purge binlogs
+#
+--error 1220
+show binlog events in 'non existing_binlog_file';
+purge master logs before now();
+--error 1220
+show binlog events in '';
+purge master logs before now();
+
+--echo End of 5.0 tests

sql/sql_repl.cc

@@ -1420,13 +1420,11 @@ bool mysql_show_binlog_events(THD* thd)
   }
 
   if (errmsg)
-  {
     my_error(ER_ERROR_WHEN_EXECUTING_COMMAND, MYF(0),
              "SHOW BINLOG EVENTS", errmsg);
-    DBUG_RETURN(TRUE);
-  }
+  else
+    send_eof(thd);
 
-  send_eof(thd);
   pthread_mutex_lock(&LOCK_thread_count);
   thd->current_linfo = 0;
   pthread_mutex_unlock(&LOCK_thread_count);