Bugfix. Local variables are now initialized to null.

mysql-test/r/sp.result:
  New test case for bugfix (when a variable is not set due to an exception).
mysql-test/t/sp.test:
  New test case for bugfix (when a variable is not set due to an exception).
sql/item.h:
  Local variables are initialized to null.
sql/sp_head.cc:
  Local variables are initialized to null.

mysql-test/r/sp.result

@@ -514,6 +514,22 @@ id	data
 hndlr3	13
 delete from t1;
 drop procedure hndlr3;
+create procedure hndlr4()
+begin
+declare x int default 0;
+declare val int;	                           # No default
+declare continue handler for sqlexception set x=1;
+select data into val from test.t1 where id='z' limit 1;  # No hits
+if val < 10 then
+insert into test.t1 values ('z', 10);
+end if;
+end;
+call hndlr4();
+select * from t1;
+id	data
+z	10
+delete from t1;
+drop procedure hndlr4;
 create procedure cur1()
 begin
 declare done int default 0;

mysql-test/t/sp.test

@@ -604,6 +604,29 @@ select * from t1|
 delete from t1|
 drop procedure hndlr3|
 
+
+# Variables might be uninitialized when using handlers
+# (Otherwise the compiler can detect if a variable is not set, but
+#  not in this case.)
+create procedure hndlr4()
+begin
+  declare x int default 0;
+  declare val int;	                           # No default
+  declare continue handler for sqlexception set x=1;
+
+  select data into val from test.t1 where id='z' limit 1;  # No hits
+
+  if val < 10 then
+    insert into test.t1 values ('z', 10);
+  end if;
+end|
+
+call hndlr4()|
+select * from t1|
+delete from t1|
+drop procedure hndlr4|
+
+
 #
 # Cursors
 #

sql/item.h

@@ -229,7 +229,9 @@ class Item_splocal : public Item
 
   Item_splocal(uint offset)
     : m_offset(offset)
-  {}
+  {
+    Item::maybe_null= TRUE;
+  }
 
   Item *this_item();
   Item *this_const_item() const;

sql/sp_head.cc

@@ -401,11 +401,17 @@ sp_head::execute_procedure(THD *thd, List<Item> *args)
     close_thread_tables(thd);
 
     // The rest of the frame are local variables which are all IN.
-    // QQ We haven't found any hint of what the value is when unassigned,
-    //    so we set it to NULL for now. It's an error to refer to an
-    //    unassigned variable anyway (which should be detected by the parser).
-    for (; i < csize ; i++)
-      nctx->push_item(NULL);
+    // Default all variables to null (those with default clauses will
+    // be set by an set instruction).
+    {
+      Item_null *nit= NULL;	// Re-use this, and only create if needed
+      for (; i < csize ; i++)
+      {
+	if (! nit)
+	  nit= new Item_null();
+	nctx->push_item(nit);
+      }
+    }
     thd->spcont= nctx;
   }