Have you ever accidentally written code like this?

procedure Example_Proc (X : out Boolean) is
begin
   null; -- Do something, but do not touch X
end Example_Proc;

with Example_Proc;
procedure Main is
   My_Flag : Boolean;
begin
   Example_Proc (My_Flag);
end Main;

In the above code, parameter X with mode "out" is left untouched. Because of this, value of My_Flag is undefined after Example_Proc (My_Flag) call.

To prevent mistakes like this, you can use Adacontrol and a rule:

check improper_initialization (out_parameter);

With the rule, Adacontrol will warn you about your mistake:

$ adactl -f rules.aru example_proc.adb example_proc.ads main.adb
example_proc.adb:1:25: Error: IMPROPER_INITIALIZATION: out parameter "X" not safely initialized
$