bug#47049: [feature/native] macro-expansion cycle when compiling comp.el

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> > I made some local modifications in comp.el, and used that modified
>> > comp.el for a while (by loading it manually at run time) to debug some
>> > problem.  Then I undid those local modifications of comp.el (by saying
>> > "git checkout") and said "make" to rebuild Emacs.  And I see this:
>> >
>> >     ELC      emacs-lisp/comp.elc
>> >   Warning: Eager macro-expansion skipped due to cycle:
>> >       => (load "comp.el") => (macroexpand-all (defalias 'comp-add-call-cstr  )) => (macroexpand (comp-loop-insn-in-block  )) => (load "comp.el")
>> >
>> > Why does this happen?
>> 
>> I'm not sure, but I can reproduce it.
>> 
>> I guess (just a guess) it might be because `comp-add-call-cstr' is using
>> a macro `comp-loop-insn-in-block' that is expanding with a
>> `cl-symbol-macrolet' inside? (no idea why this should be a problem).
>> 
>> > could it be that while comp.el was modified it
>> > got native-compiled, and now that inconsistent comp.eln gets in the
>> > way?
>> 
>> I think this has not to do specifically with native compilation.
>> 
>> I see it goes away removing '(setq load-prefer-newer t)' from the
>> invocation tho.
>> 
>> Perhaps somebody already more into the macro expansion business might
>> have some suggestion.
>
> Stefan, can you help, please?

Nothing jumps at me by looking at the code.  I'll have to look at the
actual complete stacktrace I think.


        Stefan