Re: Two strange messages while building Emacs on MS-Windows

[Stefan Monnier]

> But, why the makefiles don't take care all necessary recompilations?

Several reasons:
- there is no tool that extracts dependencies between Elisp files, so we
  don't have the needed dependency data.
- if you try to make such a tool you'll find that we have a lot of
  (apparently) circular dependencies.
- unless the dependency management is very clever, it will tend to
  recompile everything whenever a change is made to one of the
  "core" files.  E.g.: the .elc files depend on bytecomp.elc.
  bytecomp.elc is generated from the "emacs" executable which required
  many elisp files like subr.el(c), mule.el(c), help.el(c), so any
  change to one of these files causes generation of a new "emacs"
  executable, which in turn would cause recompilation of bytecomp.elc
  and (pretty much) all other .elc files.

So the "naive right way" quickly degenerates to something very close to
"make bootstrap".  But in 99% of the cases, only the modified files
require recompilation, so the default is to be incorrect.
Hopefully, at some point, we'll be able to do better.


        Stefan