Re: Y21C Bug

["Thierry Lelegard" <lelegard@club-internet.fr>]

> > I think on DEC Ada on VAX/VMS, the executable file would *not* contain
> > all those zeros -- just an indication that the OS should create them as
> > zero if and when necessary.  (Assuming One_Zillion is made small enough
> > that the compiler doesn't blow up.)
> 
> I think it does, even it they are all zeros. I ran in that problem a few times.

Yes it does. If you had left the variable uninitialized (on an Ada
perspective), then the variable would have been allocated in
a "demand zero" section (no allocation in executable). Since
you provided an explicit initial value, the compiler/linker placed
it into a "copy on reference" section which contains the initial
values. Of course, the compiler could make a special optimization
which consists in inspecting every single byte of this initial
value and if they are all zeroes then place the variable into
a "demand zero" section. But, it appears that this optimization
is not made.

By the way, for some obscure reasons I used to know (but that I
forgot), the VMS linker never creates "demand zero" sections in
shareable images ("DLL" for users of dummy OS). They are turned
into "copy on reference" sections filled with zeroes. "Demand zero"
sections apply to executable images only.

-Thierry
________________________________________________________
Thierry Lelegard, Paris, France
E-mail: lelegard@club-internet.fr