Stepping back from everything that's already been suggested, when I wrote
this from scratch, I used something simpler:
MACRO ,
&LABEL DIAG &RX,&RY,&DISP
&LABEL DC 0H,X'83',AL.4(&RX,&RY),Y(&DISP)
MEND ,
The overwriting of another instruction seems unneccesarily complex. I'm
guessing that the intent was to allow the assembler to produce register
cross-reference entries, but some Diags use only Rx and not Ry, some use an
implied Rx+1 and Ry+1, etc., which means that (the lack of) any
cross-reference entries can't be trusted anyway. If the overwriting was
done for another reason, hopefully someone will let me know.
- mb
IBM Mainframe Assembler List <[email protected]> wrote on
12/21/2013 03:11:29 PM:
> From: Mark Boonie/Poughkeepsie/IBM@IBMUS
> To: [email protected],
> Date: 12/21/2013 03:14 PM
> Subject: Re: macros to implement opcodes
> Sent by: IBM Mainframe Assembler List <[email protected]>
>
> Like John Gilmore, I (strongly) dislike hard-coded 3's and 4's,
especially
> when a macro generates several instructions that must be ORG'ed into and
> around. Labels are our friends. If I were writing this macro and found
> that the user-supplied label was optional, I would probably write code to
> generate my own label and ORG to that. In fact, I'd probably also define
a
> label that follows the generated instruction and ORG back to that. But,
I
> would hazard a guess that these are techniques that most of us are
already
> aware of.
>
> - mb
>
> IBM Mainframe Assembler List <[email protected]> wrote on
> 12/21/2013 01:20:48 PM:
>
> > From: John Gilmore <[email protected]>
> > To: [email protected],
> > Date: 12/21/2013 01:23 PM
> > Subject: Re: macros to implement opcodes
> > Sent by: IBM Mainframe Assembler List <[email protected]>
> >
> > Steve Comstock wrote:
> >
> > <begin extract>
> > Neither version is bullet proof, but Ed's works in both cases of a
> > label supplied or not (neither of which is an error, so 'bullet
> > proofing' for a missing label is really irrelevant).
> > </end extract>
> >
> > and this---Let me quote him---is
> >
> > Nonsense!
> >
> > When someone writes a macro definition he or she is free to make the
> > omission of or a putatively inappropriate value of any symbolic
> > parameter an error, as I did with the skeletal sample lines that
> > tested for the presence or absence of a label in the DIAG macro
> > instruction. In general the omission of a label may be innocuous in
> > one context and a severe error in another, in the judgment of the
> > writer of a particular macro instruction.
> >
> > Bullet proofing is never irrelevant. It is tedious, certainly; but
> > the only appropriate stance for the writer of a production macro
> > definition is that those who write macro instructions that use it will
> > be ignorant, malicious or perhaps both.
> >
> > Ed Jaffe's point is more substantial; but, as he well knows, there are
> > simple ways to guard against the difficulty he raised. Indeed, there
> > are alternative ways to induce the assembler to do the necessary
> > arithmetic without resort to the magic numbers 3 and 4, which still
> > seem to me to be ugly.
> >
> > I do not at all mind being ganged up upon. Let's do it again sometime
> soon.
> >
> >
> > John Gilmore, Ashland, MA 01721 - USA
> >
