bug#58429: 29.0.50; inhibit-automatic-native-compilation does not work as expected.

[Andrea Corallo]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Andrea Corallo <akrl@sdf.org>
>> Cc: max.brieiev@gmail.com, larsi@gnus.org, 58429@debbugs.gnu.org
>> Date: Fri, 14 Oct 2022 20:10:57 +0000
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> >   If non-nil enable primitive trampoline synthesis.
>> >   This makes primitive functions redefinable or advisable effectively.
>> >
>> > which seems to hint that when this is nil, primitives cannot be
>> > advised or redefined?
>> 
>> They can, but they will not take effect on Lisp code that is native
>> compiled (at speed 2), similarly to when they are called from C code.
>> 
>> > We set this variable to nil in startup.el if
>> > native-comp-available-p returns nil (which currently can only happen
>> > on MS-Windows), AFAIU with the intent to prevent Emacs from even
>> > trying to natively-compile anything, including trampolines.  But if
>> > Emacs cannot produce a trampoline, it means that primitives cannot be
>> > redefined, and we silently fail that?  Because (again, AFAIU)
>> > native-comp-available-p being nil does not prevent Emacs from loading
>> > *.eln files that are already compiled (because just loading them
>> > doesn't need libgccjit), is that right?
>> 
>> Correct, as you said Emacs will work, only we can't guarantee that
>> primitive redefinition will take the effect expected by the user (unless
>> of course trampolines were precompiled, in that case it's all good).
>
> Thanks.  I therefore extended the doc string of this variable (on the
> emacs-28 branch) to make this crystal clear.

Thanks