Re: More reliable byte compilation, take 45

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

>> Converting a `.elc` file to a `.eln` file can be done by a pure function
>> with no need for any extra information.
> I very much doubt that.

You might be right, there might be corner cases I'm not taking into
account, but by and large it should be the case.  At least much more so
than for `.el` files where it's clearly a real problem.

> I have no reason to believe that the problems we see with native
> compilation are related to these aspects.

I'm not sure which problems you're referring to.
Within the context of Emacs's own ELisp files, this should never be
an issue.

> Do you have evidence of that?

IIRC, in Raman's case the evidence was that the `.eln` file was calling
a macro as if it were a function, and that this didn't happen when using
the `.elc` file.  These problems typically happen when a `.el` file is
miscompiled because some other ELisp file was not loaded beforehand.

Admittedly, I don't have actual evidence, but it seemed to hint at that.

In any case, the problem with compiling from the `.el` file instead of
from the `.elc` file is real and it's easy to trigger it on purpose.
The only question for me is how often it will bite us out there in the
real world.

There's a chance that it will simply encourage people to fix their ELisp
files to better follow the (undocumented) conventions, so to some degree
I agree that it might be preferable not to fix this issue.


        Stefan