bug#46502: 28.0.50; [feature/native-comp] (d3a399dd) native-comp bootstrap failure

[Andrea Corallo]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Pip Cet <pipcet@gmail.com>
>> Date: Fri, 19 Feb 2021 13:31:49 +0000
>> Cc: akrl@sdf.org, mwd@md5i.com, 46502@debbugs.gnu.org
>> 
>> > > One thing I've noticed in my experiments is that many builds that are
>> > > interrupted at the wrong point and then resumed produce different
>> > > results. I.e. you type "make", then hit Ctrl-C at the wrong time, then
>> > > type "make" again and you get a different result.
>> >
>> > What does "different result" mean in this case? is the produced .eln
>> > file different? or something else?
>> 
>> There are differences both in the .elc and .eln, and I saw different
>> success/failure behavior but only with local modifications.
>
> Let's talk about *.elc files first, as this is not supposed to happen.
> AFAIR, we write the bytecode into a temporary file, and then rename it
> atomically only when the compilation finishes successfully.  So
> interrupting should not do any harm, and therefore I'm curious what
> kind of differences in *.elc files do you see in these cases.

In native-comp this is very similar, the elc renaming is postponed to be
done when native compilation is done and the temporary eln has been
renamed to its final name.  As eln compilation is triggered by the elc
targets this is supposed to work, or at least it *should* as it does on
master.

  Andrea