Fixes and test cases for Bug#8880 "Commands out of sync error with cursors"

 and Bug#9159 "Server crash during mysql_stmt_close".
The patch adds support for single-row result sets in cursors.


libmysql/libmysql.c:
  If we wanted a cursor, and the server wasn't able to create one,
  buffer all rows on client. Currently this is possible only for
  single row result sets and some SHOW commands.
sql/sql_prepare.cc:
  Properly free resources if there was a request to open a cursor which
  wasn't fullfilled.
  Give error on attempt to open a cursor for a statement not returning
  a result set.
sql/sql_select.h:
  Initialize Item_arena of Cursor object. A case when a cursor object
  is created but not used is possible with single-row result sets.
tests/mysql_client_test.c:
  Test cases for Bug#8880 and Bug#9159

1 files changed, 8 insertions, 6 deletions

diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index 7862717bb18..75027b3bb0a 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -1970,6 +1970,7 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
 {
   ulong stmt_id= uint4korr(packet);
   ulong flags= (ulong) ((uchar) packet[4]);
+  Cursor *cursor= 0;
   /*
     Query text for binary log, or empty string if the query is not put into
     binary log.
@@ -2007,15 +2008,17 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
         statement: we can't open a cursor for it.
       */
       flags= 0;
+      my_error(ER_SP_BAD_CURSOR_QUERY, MYF(0));
+      goto err;
     }
     else
     {
       DBUG_PRINT("info",("Using READ_ONLY cursor"));
       if (!stmt->cursor &&
-          !(stmt->cursor= new (&stmt->main_mem_root) Cursor()))
+          !(cursor= stmt->cursor= new (&stmt->main_mem_root) Cursor()))
         DBUG_VOID_RETURN;
       /* If lex->result is set, mysql_execute_command will use it */
-      stmt->lex->result= &stmt->cursor->result;
+      stmt->lex->result= &cursor->result;
     }
   }
 #ifndef EMBEDDED_LIBRARY
@@ -2061,11 +2064,10 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
     my_pthread_setprio(pthread_self(), WAIT_PRIOR);
   thd->protocol= &thd->protocol_simple;         // Use normal protocol
 
-  if (flags & (ulong) CURSOR_TYPE_READ_ONLY)
+  if (cursor && cursor->is_open())
   {
-    if (stmt->cursor->is_open())
-      stmt->cursor->init_from_thd(thd);
-    stmt->cursor->state= stmt->state;
+    cursor->init_from_thd(thd);
+    cursor->state= stmt->state;
   }
   else
   {