Re: Disabling string evaluation in a logging system

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Wed, 19 May 2010 05:04:32 -0400, Stephen Leake wrote:

> dhenry <tfc.duke@gmail.com> writes:
> 
>> As Dmitry said, the log level may dynamically change. Therefore,
>> inlining in order to let the compiler do the optimization doesn't
>> work.
> 
> I don't follow this. Inlining is the same as writing the if-test.

That depends on the compiler.

procedure Log (Barrier : Boolean; Message : String) is
begin
   if Barrier then
      Put (Message);
   end if;
end Log;

can be inlined as:

1. moving evaluation of temporaries down:

   declare
      Barrier : constant Boolean := <condition-expression>;
   begin
      if Barrier then
         declare
            Message : constant String := <message-expression>;
         begin
            Put (Message);
         end;
      end if;
   end;

or as

2. moving evaluation of temporaries up:

   declare
      Barrier : constant Boolean := <condition-expression>;
      Message : constant String := <message-expression>;
   begin
      if Barrier then
        Put (Message);
      end if;
   end;

The language mandates nothing regarding this. The compiler can even ignore
the pragma Inline.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de