Ubuntu 19.10 will be 64 bit only

[Erich E. Hoover]

On Fri, Jun 21, 2019 at 9:03 AM Dmitry Timoshkov <dmitry at baikal.ru> wrote:
>
> "Erich E. Hoover" <erich.e.hoover at gmail.com> wrote:
>
> > On Fri, Jun 21, 2019 at 6:41 AM Rosanne DiMesio <dimesio at earthlink.net> wrote:
> > > ...
> > > I'm not qualified to explain the technical issues, beyond saying Wine does it the same way as Windows (WoW64). I need help framing an answer in terms a typical Ubuntu user can understand that I can put in the FAQ and on the forum.
> >
> > Well, part of the problem is that we don't implement WoW64 the exact
> > same way Windows does.  All the 32-bit Windows routines have thunks
> > that transition to 64-bit code, call the 64-bit API equivalent, and
> > then transition back to 32-bit code.
>
> That's probably true only for low level things like ntdll, user32, gdi32
> and ws2_32, but everything else that doesn't need to access kernel level
> OS functionality (like gdiplus/windowscodecs) don't need to perform the
> 32-bit to 64-bit transition.

That's my understanding as well, I was trying to give a quick summary
- "all" was probably a poor choice of words.

> >  Our 32-bit libraries call the
> > 32-bit Linux equivalents, since this is massively easier and "just
> > works".  I vaguely remember a conversation a number of years ago where
> > someone talked about doing similar thunking to Windows and there was
> > concern that it is too hard to get this thunking correct for every API
> > call, but I don't remember the details as to why that's the case.
>
> win16 is very small in comparison with win32, so it was relatively easy
> to implement it on top of 32-bit code, it's practically impossible to do
> the same thing to implement 32-bit on top of 64-bit.

I would assume that we would keep as much as possible as 32-bit and,
like Windows, only transition to 64-bit in places where we absolutely
have to (such as when we need to call system libraries).  Don't get me
wrong, this is still a _ton_ of work, but I believe that when someone
brought this up before that there was a technical limitation that
prevented us from doing this at all and I've forgotten what was said.

Best,
Erich