Fix BUG#2259: Crash after fetch from not-open cursor in stored procedure

Initialize and test properly when cleaning up, to avoid crash in some error cases.

mysql-test/r/sp-error.result

@@ -283,6 +283,15 @@ create table t3 (column_1 int)|
 call bug1653()|
 drop procedure bug1653|
 drop table t3|
+create procedure bug2259()
+begin
+declare v1 int;
+declare c1 cursor for select s1 from t10;
+fetch c1 into v1;
+end|
+call bug2259()|
+ERROR 24000: Cursor is not open
+drop procedure bug2259|
 create procedure bug2272()
 begin
 declare v int;
@@ -292,4 +301,5 @@ insert into t1 values (666, 51.3)|
 call bug2272()|
 ERROR 42S22: Unknown column 'v' in 'field list'
 delete from t1|
+drop procedure bug2272|
 drop table t1|

mysql-test/t/sp-error.test

@@ -388,6 +388,23 @@ call bug1653()|
 drop procedure bug1653|
 drop table t3|
 
+#
+# BUG#2259
+#
+# Note: When this bug existed, it did not necessarily cause a crash
+#       in all builds, but valgrind did give warnings.
+create procedure bug2259()
+begin
+  declare v1 int;
+  declare c1 cursor for select s1 from t10;
+
+  fetch c1 into v1;
+end|
+
+--error 1310
+call bug2259()|
+drop procedure bug2259|
+
 #
 # BUG#2272
 #
@@ -402,6 +419,7 @@ insert into t1 values (666, 51.3)|
 --error 1054
 call bug2272()|
 delete from t1|
+drop procedure bug2272|
 
 drop table t1|
 

sql/sp_rcontext.cc

@@ -176,10 +176,13 @@ sp_cursor::close(THD *thd)
 void
 sp_cursor::destroy()
 {
-  delete m_prot;
-  m_prot= NULL;
-  free_root(&m_mem_root, MYF(0));
-  bzero((char *)&m_mem_root, sizeof(m_mem_root));
+  if (m_prot)
+  {
+    delete m_prot;
+    m_prot= NULL;
+    free_root(&m_mem_root, MYF(0));
+    bzero((char *)&m_mem_root, sizeof(m_mem_root));
+  }
   m_isopen= FALSE;
 }
 
@@ -190,14 +193,12 @@ sp_cursor::fetch(THD *thd, List<struct sp_pvar> *vars)
   sp_pvar_t *pv;
   MYSQL_ROW row;
   uint fldcount;
-  MYSQL_FIELD *fields= m_prot->fields;
 
   if (! m_isopen)
   {
     send_error(thd, ER_SP_CURSOR_NOT_OPEN);
     return -1;
   }
-
   if (m_current_row == NULL)
   {
     send_error(thd, ER_SP_FETCH_NO_DATA);

sql/sp_rcontext.h

@@ -205,7 +205,7 @@ class sp_cursor : public Sql_alloc
 public:
 
   sp_cursor(LEX *lex)
-    : m_lex(lex), m_isopen(0), m_current_row(NULL)
+    : m_lex(lex), m_prot(NULL), m_isopen(0), m_current_row(NULL)
   {
     /* Empty */
   }