Spacemacs experimental features

Spacemacs dumps using the portable dumper
- Setup
- Usage

Spacemacs dumps using the portable dumper

The portable dumper is a feature that may be availabe with Emacs 27.1, for now its code is in the pdumper branch of the Emacs Git repository, it has not been merged to master yet.

This should theoretically work on all the three major OSes: GNU/Linux, MacOS and Windows.

Setup

To test the portable dumper with Spacemacs, follow these steps:

Clone Emacs

Clone Emacs from https://git.savannah.gnu.org/git/emacs.git:

  git clone https://git.savannah.gnu.org/git/emacs.git
  cd emacs
  git checkout pdumper

Simple patch of Emacs source code

We need to increase the number of remember_data slots in src/pdumper.c, we double the number of slots by replacing 32 with 64:

static struct
{
  void *mem;
  int sz;
} remembered_data[64];

Compile Emacs from source

This step depends on your OS (please create a PR to add the instructions for your OS).

MacOS

In the root directory of your freshly cloned Emacs repository and with the pdumper branch as the current branch:

  ./autogen.sh
  ./configure --with-ns --with-dbus --with-gnutls --with-imagemagick --with-rsvg  --with-mailutils --with-xml2 --with-modules

Update your dotfile

A new user dotfile function has been added which is called before doing the dump. The function name is dotspacemacs/user-load.

You can copy/paste the following snippet in your dotfile and provide a value for dotspacemacs-emacs-pdumper-executable-file which must point to the Emacs executable you compiled at the previous step. For me it was: "~/dev/emacs/src/emacs"

(defun dotspacemacs/user-load ()
  "Library to load while dumping.
This function is called while dumping Spacemacs configuration. You can
`require' or `load' the libraries of your choice that will be included
in the dump."
  (setq-default

   ;; Absolute file path pointing to emacs 27.1 executable compiled with support
   ;; for the portable dumper (this is currently the branch pdumper)
   ;; If nil then automatic Emacs dump is disabled.
   ;; (default nil)
   dotspacemacs-emacs-pdumper-executable-file nil

   ;; File path of Spacemacs dump file. This is the file created by the portable
   ;; dumper. To load it when starting Emacs add the parameter `--dump-file'
   ;; when invoking Emacs 27.1 executable on the command line, for instance:
   ;;   ./emacs --dump-file=spacemacs.pdump
   ;; If the file path is relative, it will be relative to the directory pointed
   ;; by `dotspacemacs-emacs-pdumper-executable-file'.
   ;; (default spacemacs.pdmp)
   dotspacemacs-emacs-dumper-dump-file "spacemacs.pdmp"))

Test

Checkout the moon branch in `.emacs.d` and launch your Emacs as you usually do. It can be Emacs 25.1 or later this is not important but obviously you can also use the compiled Emacs version.

Each time Emacs starts, Spacemacs will check if the list of your layers has changed, if it has changed then Emacs will be automatically dumped for you in an asynchronous process. The buffer for the output of the process is named *spacemacs dumper*.

If you have no error during the dump you can test it out!

To actually start Spacemacs with the compiled Emacs 27.1 and the Spacemacs dump, on the command line in the src directory of the cloned Emacs source:

  ./emacs --dump-file=spacemacs.pdmp &

Report issues

If you want to report an issue regarding this new feature please use the label Portable Dumper.

All the related issues can be found with this link.

Usage

Once dotspacemacs-emacs-pdumper-executable-file is set to a non-nil and valid file path to an Emacs 27.1 executable Emacs will be redumped automatically each time the layer list changes or the --force-dump parameter is passed on the command line.

To use the created dump file, open a shell in the src directory of the cloned Emacs source and type:

  ./emacs --dump-file=spacemacs.pdmp &

spacemacs.pdmp corresponds the value of the variable dotspacemacs-emacs-dumper-dump-file.

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