Re: Merging MPS a.k.a. scratch/igc, yet again

["Óscar Fuentes" <ofv@wanadoo.es>]

Xiyue Deng <manphiz@gmail.com> writes:

> If making MPS available in Debian would help Emacs packaging I'm willing
> to work on this (in the coming weeks as igc may not land with the
> upcoming Emacs 30 release so not in a hurry.)

As a Debian user, I value every package that is made available through
its repos, thank you.

However, in the specific case of Emacs/MPS, IMAO distro packaging is not
the best way, because:

* Depending on packaged MPS brings versioning problems, not to mention
  that it would take a long time to have MPS available on a large part
  of the distro ecosystem. We would need the DIY part of README-IGC
  anyway.

* It is very likely that we end doing some patching to the MPS sources
  to adapt to our specific needs (if those patches end upstream or not,
  that's another question.)

* MPS does a performance-critical job. Using it as a shared object might
  incur in a performance penalty. Having it in source form alongside the
  Emacs sources will result in opportunities for optimizations (LTO,
  PGO, ...) that may bring better performance.

* MPS does a correctness-critical job. Depending on multiple external
  sources for such core component is a recipe for problems (future
  changes by the MPS maintainers, patching by packagers, buggy
  compilers, etc.) We need to keep a close watch on what MPS incarnation
  we use. Better yet, total control.

For those reasons, incorporating MPS into the Emacs sources is the right
thing to do.