Re: Array and memory usage

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Preben Randhol <randhol+news@pvv.org> writes:

> John R. Strohm wrote:
> > "Preben Randhol" <randhol+news@pvv.org> wrote in message
> > news:slrnb6m8mg.15o.randhol+news@kiuk0152.chembio.ntnu.no...
> >> I was a bit puzzeled to see that if I do:
> >>
> >>    type Str_Array_Type is array (1 .. 1000) of String (1 .. 800);
> >>
> >>    type User_Data is
> >>       record
> >>          Name     : Str_Array_Type;
> >>          Hostname : Str_Array_Type;
> >>       end record;
> > 
> > This declares two types and NO instances of those types.
> > 
> >> my program uses 800 bytes of memory, while if I only change the program
> >> like this:
> >>
> >>    type User_Data is
> >>       record
> >>          Name     : Str_Array_Type := (others => (others => ' '));
> >>          Hostname : Str_Array_Type := (others => (others => ' '));
> >>       end record;
> >>
> >> then the program uses 2356 bytes.
> > 
> > This declares the same two types and TWO (2) implicit instances of
> > Str_Array_Type, namely, the aggregate constants.  That's where the
> > difference comes from.

A good compiler will not do that, especially if the object is statically
allocated.

- Bob