Re: Redefining a DS

[Vern Hamberg <vhamberg@xxxxxxxxxxx>]

I thought memcpy is a C function - there is no implicit connection to 
anything on the i. How it's implemented depends on whatever version of 
C/C++ you use. If it has been a direct mapping to some MI function - 
well, we can't depend on that, cuz implementation changes as better ways 
are found. And I'd be very surprised to be able to depend on this

The C memcpy has this prototype

    void * /memcpy/ ( void * destination, const void * source, size_t num )

The MI memcpy has this prototype

    MEMCPY (

       target_string   : address of aggregate(*)
       source_string   : address of aggregate(*)
       copy_length     : unsigned binary(4) value which specifies the
                         number of bytes to copy
) 

Similar. Now which memcpy do you run when you use it? I don't know. If 
you use _memcpy, that's most probably MI.

You also mention MI and assembler together - they are not the same on 
the i - there is assembly language on i - you can see it in STRSST, I 
believe. And if you take the disassemble option there, you don't get MI 
code. I've actually walked assembly in the lab. And must admit to not 
knowing enough to make it useful - have barely touched a little 
Microsoft assembly in my youth!

Confused on a Sunday!

Vern

Dennis Lovelady wrote:
> > > > It turns out (or appears)
> > > > that the MI is pulling some tricks under the covers.
> > > >
> > > >         
> > > Probably not the MI but rather the compiler.
> > >
> > >       
> > This is probably the source of the confusion.  RPG doesn't expect you
> > to
> > be using assembly language tricks to initialize a buffer, because you
> > can do it in other ways.  Although I don't see an EASY way of
> > initializing a buffer to a computed value.  You can do it with a little
> > trickery (basing an array, for example), but nothing quite as simple as
> > the overlapping move.
> >     
>
> Isn't memcpy supposed to be a direct link to the MI instruction?  If so, I
> think we can take the responsibility for this one away from the RPG
> compiler.  If not, then what the heck is it?!?  An emulation of an
> emulation?
>
> Maybe I'll try this in MI later today.
>
> Dennis Lovelady
> http://www.linkedin.com/in/dennislovelady
> --
> "Experience is the name everyone gives to their mistakes."
>         -- Oscar Wilde
>
>