bug#6958

Fixed that negative arguments to certain integer options wrap around.

mysql-test/r/variables.result

@@ -482,3 +482,8 @@ SET GLOBAL MYISAM_DATA_POINTER_SIZE= 8;
 SHOW VARIABLES LIKE 'MYISAM_DATA_POINTER_SIZE';
 Variable_name	Value
 myisam_data_pointer_size	8
+SET GLOBAL table_cache=-1;
+SHOW VARIABLES LIKE 'table_cache';
+Variable_name	Value
+table_cache	1
+SET GLOBAL table_cache=DEFAULT;

mysql-test/t/variables.test

@@ -362,3 +362,11 @@ drop table t1;
 
 SET GLOBAL MYISAM_DATA_POINTER_SIZE= 8;
 SHOW VARIABLES LIKE 'MYISAM_DATA_POINTER_SIZE';
+
+#
+# Bug #6958: negative arguments to integer options wrap around
+#
+
+SET GLOBAL table_cache=-1;
+SHOW VARIABLES LIKE 'table_cache';
+SET GLOBAL table_cache=DEFAULT;

sql/set_var.cc

@@ -1223,6 +1223,12 @@ static void fix_server_id(THD *thd, enum_var_type type)
   server_id_supplied = 1;
 }
 
+bool sys_var_long_ptr::check(THD *thd, set_var *var)
+{
+  longlong v= var->value->val_int();
+  var->save_result.ulonglong_value= v < 0 ? 0 : v;
+  return 0;
+}
 
 bool sys_var_long_ptr::update(THD *thd, set_var *var)
 {

sql/set_var.h

@@ -93,6 +93,7 @@ public:
   sys_var_long_ptr(const char *name_arg, ulong *value_ptr,
 		   sys_after_update_func func)
     :sys_var(name_arg,func), value(value_ptr) {}
+  bool check(THD *thd, set_var *var);
   bool update(THD *thd, set_var *var);
   void set_default(THD *thd, enum_var_type type);
   SHOW_TYPE type() { return SHOW_LONG; }