fix for Bug #12979 Stored procedures: crash if inout decimal parameter

mysql-test/r/sp.result:
  fix result
mysql-test/r/type_newdecimal.result:
  fix result
mysql-test/t/sp.test:
  add a test for the bug
mysql-test/t/type_newdecimal.test:
  add a test for the bug
sql/item_func.cc:
  call correct method of the item

mysql-test/r/sp.result

@@ -3331,4 +3331,20 @@ set @x=y;
 end|
 call bug13124()|
 drop procedure  bug13124|
+drop procedure if exists bug12979_1|
+create procedure bug12979_1(inout d decimal(5)) set d = d / 2|
+set @bug12979_user_var = NULL|
+call bug12979_1(@bug12979_user_var)|
+drop procedure bug12979_1|
+drop procedure if exists bug12979_2|
+create procedure bug12979_2()
+begin
+declare internal_var decimal(5);
+set internal_var= internal_var / 2;
+select internal_var;
+end|
+call bug12979_2()|
+internal_var
+NULL
+drop procedure bug12979_2|
 drop table t1,t2;

mysql-test/r/type_newdecimal.result

@@ -1016,3 +1016,6 @@ v	tdec
 v	tdec
 9	0
 drop procedure wg2;
+select cast(@non_existing_user_var/2 as DECIMAL);
+cast(@non_existing_user_var/2 as DECIMAL)
+NULL

mysql-test/t/sp.test

@@ -4177,6 +4177,35 @@ end|
 call bug13124()|
 drop procedure  bug13124|
 
+#
+# Bug #12979  Stored procedures: crash if inout decimal parameter
+#
+
+# check NULL inout parameters processing
+
+--disable_warnings
+drop procedure if exists bug12979_1|
+--enable_warnings
+create procedure bug12979_1(inout d decimal(5)) set d = d / 2|
+set @bug12979_user_var = NULL|
+call bug12979_1(@bug12979_user_var)|
+drop procedure bug12979_1|
+
+# check NULL local variables processing
+
+--disable_warnings
+drop procedure if exists bug12979_2|
+--enable_warnings
+create procedure bug12979_2()
+begin
+declare internal_var decimal(5);
+set internal_var= internal_var / 2;
+select internal_var;
+end|
+call bug12979_2()|
+drop procedure bug12979_2|
+
+
 #
 # BUG#NNNN: New bug synopsis
 #

mysql-test/t/type_newdecimal.test

@@ -1037,3 +1037,10 @@ call wg2()//
 
 delimiter ;//
 drop procedure wg2;
+
+#
+# Bug #12979 Stored procedures: crash if inout decimal parameter
+# (not a SP bug in fact)
+#
+
+select cast(@non_existing_user_var/2 as DECIMAL);

sql/item_func.cc

@@ -765,7 +765,7 @@ my_decimal *Item_func_numhybrid::val_decimal(my_decimal *decimal_value)
   }
   case REAL_RESULT:
   {
-    double result= (double)int_op();
+    double result= (double)real_op();
     double2my_decimal(E_DEC_FATAL_ERROR, result, decimal_value);
     break;
   }