Re: [PATCH] Project out of sources compilation

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 04 Apr 2024 20:15:56 +0200
> From: Ergus <spacibba@aol.com>
> CC: Hi-Angel@yandex.ru, rms@gnu.org, dmitry@gutov.dev
> 
> >> Exactly, so this is not OOSC and does not behave as expected in
> >> OOSC.
> >
> >No, it isn't.  Not many programs at all support running uninstalled.
> 
> All CMake and Meson programs do it by default. Mainly because they also provide test features  where the executables are supposed to be tested before calling install or pack.

I don't see how CMake or Meson can make a program run uninstalled,
unless the program already provides the necessary features for doing
so.  Imagine a program that needs to read some data files, which it
expects to find in a directory under /usr/share whose absolute file
name is hard-coded into it, as determined from --prefix at configure
time.  Such a program cannot run uninstalled, because the files in
/usr/share are not yet installed.

Emacs needs to know where to find the Lisp files it loads on demand.
If those files are in the place configured via --prefix, they can be
found easily, but if Emacs runs uninstalled, the Lisp files are not
there, and Emacs needs to find them somehow.  Unless someone writes
code to look for them in the right places, there's no way CMake or
Meson or any other general-purpose tool could fix that.