Re: [PATCH] xen/efi: Reuse PrintMessage function

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

On Fri, Jul 18, 2025 at 12:12 PM Andrew Cooper
<andrew.cooper3@xxxxxxxxxx> wrote:
>
> On 18/07/2025 10:41 am, Frediano Ziglio wrote:
> > PrintMessage function print a message string followed by a
> > new line.
> > Move the function from ARM specific code to common code.
> > Reuse it in EFI code.
> > No functional changes.
> >
> > Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
>
> Please no.
>
> Hiding \n (or \r\n) in strings is an antipattern and a source of
> confusion that we do not want in Xen.
>

I didn't realize it was not a Xen pattern. I found the thing not that
coherent between x86 and arm and attempted to fix it.

> Instead, delete PrintMessage() and convert ARM to use PrintStr().  That
> looks like it was premature anti-optimisation.  You save 4 bytes per
> string, but it costs 12 byte minimum in .text to set up the function
> call, let alone the function call itself.
>

To be honest I didn't consider this aspect and I don't feel it matters much.
Looking at other languages printing an implicit newline is pretty
common, Pascal has "Wtite" and "WtiteLn", Ocaml has "print_string" and
"print_endline", Python has an "end" parameter which by default is the
newline, Basic (if I remember) has the possibility of an implicit
empty field. In C is not so common although there's "puts" and some
functions (like "syslog") have some kind of implicit newline.
But obviously Xen is not any of them.

As I said above however my main reason is coherency so I'll post your
suggestion.

> ~Andrew

Frediano