bug#62762: circular dependencies in elisp files and make

[Max Nikulin <manikulin@gmail.com>]

On 13/05/2023 13:50, Eli Zaretskii wrote:
>> Date: Sat, 13 May 2023 10:08:25 +0700 From: Max Nikulin
>>
>> ... What
>> can be better is removing all stale .elc file before compiling of
>> updates sources. A script iterates over dependency files and deletes
>> .elc if any its prerequisite has been updated. Following compilation
>> pass can safely use .elc files that are either survived from previous
>> build as up to date or just refreshed.
> 
> So you will make each build always do two byte-compilation passes
> where today we have just one?  And the first one of these will use
> only *.el files, including for those that are preloaded into
> bootstrap-emacs?  Doesn't that sound like a significant slow-down of
> the build?

I do not see a reason for significant slow-down because I do not suggest 
two passes of *byte-compilataion*.

1. A script reads dependency files (if they exist) created during 
previous build and removes stale .elc files.
2. Normal "make" pass that takes into account dependency between files 
for ordering of compile commands. Dependency files are created or 
updated as a side-effect of compilation.

Likely it is reasonable to split stage 2 into steps similar to current 
targets like main-first and mark most of files as dependent on a target 
that (throw its dependencies) compiles files required for byte compilation.