Re: master 289000e: Merge branch 'feature/native-comp' into trunk

[Alan Mackenzie]

Hello, Eli.

On Sun, Apr 25, 2021 at 23:14:42 +0300, Eli Zaretskii wrote:
> > Date: Sun, 25 Apr 2021 20:03:46 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > Cc: emacs-devel@gnu.org

> > I've just tried a ./configure (with --with-native-compilation), and got
> > the error message:

> >     configure: error: elisp native compiler requested but libgccjit not 
> > found.
> >     Please try installing libgccjit or similar package.

> > What is libgccjit, and where do I find it?

> It's part of the GCC package, so I suggest to look among the
> GCC-related stuff that your distro offers.

Thanks, I found the Gentoo "use flag" to enable it, and rebuilt gcc.
I was then able to build Emacs including native compilation.

> > What else do I need to know, successfully to build and run the
> > native compilation feature?

> Hopefully, nothing (just to build and run).

This is sadly far from true.  You need to know basic things like native
compile files are .eln.  You need to know how to compile files.  I
guessed that

    $ emacs -Q -batch -f batch-native-compile lisp/progmodes/cc-*.el

would natively compile CC Mode.  Well, it took several minutes of
processing in which it did something, but I don't know what.  A find
failed to find '*cc-*.eln'.  On restarting Emacs, my favourite CC Mode
benchmark was only marginally (~4%) faster.

I don't know if I've actually natively compiled CC Mode, but if so, I
don't know where the compiled files are, and I don't know how to load
them into Emacs.

I'm frustrated at the moment.  I want to use this new feature, but don't
know how to, and can't find any documentation.  "native compilation"
doesn't seem to appear in either the Emacs or the Elisp manual.

-- 
Alan Mackenzie (Nuremberg, Germany).