Bug#15518 Reusing a stmt that has failed during prepare does not clear error

 - Always reset error when calling mysql_stmt_prepare a second time
 - Set stmt->state to MYSQL_STMT_INIT_DONE before closing prepared stmt in server.
 - Add test to mysql_client_test
 - Remove mysql_stmt_close in mysqltest after each query
 - Close all open statements in mysqltest if disable_ps_protocol is called. 


client/mysqltest.c:
  Don't close the statement after each query - reprepare it in next query.
  When "disable_ps_protocol" is issued make sure to close all open
  statements. Otherwise the test for @@max_prepared_statements fails. But we
  also get a test that the statements that are open can be closed and reopened
  in the middle of the tests.
libmysql/libmysql.c:
  Reset the last error every time mysql_stmt_prepare is called.
  Set state to MYSQL_STMT_INIT_DONE befoe closing it in the server. That way
  we will always have right status regardless of wheter close fails or not.
tests/mysql_client_test.c:
  Add testcase for bug15518, re-prepare a previously prepare statement that has failed
  to prepare. Test also when connection to server has been lost inbetween.
  Change all assert to DIE_UNLESS so we get printout of line and an error message
  if it fails.

1 files changed, 11 insertions, 3 deletions

diff --git a/libmysql/libmysql.c b/libmysql/libmysql.c
index 6a592f64e49..a5dcb66f002 100644
--- a/libmysql/libmysql.c
+++ b/libmysql/libmysql.c
@@ -2038,6 +2038,13 @@ mysql_stmt_prepare(MYSQL_STMT *stmt, const char *query, ulong length)
     DBUG_RETURN(1);
   }
 
+  /*
+    Reset the last error in any case: that would clear the statement
+    if the previous prepare failed.
+  */
+  stmt->last_errno= 0;
+  stmt->last_error[0]= '\0';
+
   if ((int) stmt->state > (int) MYSQL_STMT_INIT_DONE)
   {
     /* This is second prepare with another statement */
@@ -2051,23 +2058,24 @@ mysql_stmt_prepare(MYSQL_STMT *stmt, const char *query, ulong length)
     */
     stmt->bind_param_done= stmt->bind_result_done= FALSE;
     stmt->param_count= stmt->field_count= 0;
-    stmt->last_errno= 0;
-    stmt->last_error[0]= '\0';
     free_root(&stmt->mem_root, MYF(MY_KEEP_PREALLOC));
 
     int4store(buff, stmt->stmt_id);
+
     /*
+      Close statement in server
+
       If there was a 'use' result from another statement, or from
       mysql_use_result it won't be freed in mysql_stmt_free_result and
       we should get 'Commands out of sync' here.
     */
+    stmt->state= MYSQL_STMT_INIT_DONE;
     if (stmt_command(mysql, COM_STMT_CLOSE, buff, 4, stmt))
     {
       set_stmt_errmsg(stmt, mysql->net.last_error, mysql->net.last_errno,
                       mysql->net.sqlstate);
       DBUG_RETURN(1);
     }
-    stmt->state= MYSQL_STMT_INIT_DONE;
   }
 
   if (stmt_command(mysql, COM_STMT_PREPARE, query, length, stmt))