Re: Type size vs. actual size difference.

["Stanley R. Allen" <Stanley_R_Allen@raytheon.com>]

Bruce Detter wrote:
> 
> Using GNAT 3.12 on Win NT 4.0.  We have defined a record that has a length
> of 214 bytes.  The type'Size attribute reports 214, but when we declare a
> variable of the record type (X : Type) the size attribute X'Size reports
> 216.  It appears the actual variable size takes into account adjustments to
> word boundaries (and of course the type'Size attribute can't do this).  Is
> there a preprocessor command or pragma command that will force byte boundary
> alignment so that the type size agrees with the actual size?
> 

I don't think there is a standard way to do this.  On GNAT, there
is an attribute T'Object_Size, which when applied to types will yield
the number of bits that would be used for a variable if declared
"A : T;".  On the old DEC Ada compiler, you could use the attribute
T'Machine_Size, which would do the same thing.  I don't know about
other compilers.

It would be nice if something like T'Object_Size was standard.  In some
cases it's necessary for me to declare a 'dummy' variable of a type
to get this.

-- 
Stanley Allen
mailto:Stanley_R_Allen@raytheon.com