Debugging

This page explains some concepts needed to debug Spacemacs and to report issues in an useful way.

How to make a great bug report

A great bug report 🤘 should contain:

A description of your problem
The description of your system:
- Get the description of your installation
A step-by-step reproduction guide:
- Make a step-by-step reproduction guide
A backtrace (if relevant):

This is a template you can use for reporting issues on Spacemacs:

Note: Triple backquotes are not showing up because of some wiki parsing issues. Don’t forget to add them around the backtrace.

#### Description
DESCRIPTION OF THE PROBLEM

#### Reproduction guide
- Start Emacs
- REPRODUCTION STEPS

#### System Info
REPLACE THIS SECTION BY THE OUTPUT OF `SPC h d s`

#### Backtrace

BACKTRACE IF RELEVANT

You can see an example of it at the end of this page.

Get the description of your installation

The versions of software your are using can be obtained by pressing SPC h d s or M-m h d s (bind to spacemacs/describe-system-info). This will copy to the system clipboard some important information, such as your activated layers, or the Spacemacs and Emacs versions you are using.

The copied text is in markdown format, so you can paste it directly in gitter or in issues, without quoting it.

Make a step-by-step reproduction guide

Spacemacs contributors are more efficient if they have a way to reproduce the bugs on their side. For this, nothing is better than a detailed step-by-step reproduction guide. It should describe a minimal workflow that make the problem appears. It should look like a bullet-points list, beginning with “Start emacs”.

This is a good example:

Start Emacs
Open the `.spacemacs` file with SPC f e d
Search for the “dotspacemacs” with / dotspacemacs RET
Notice n and N are not working

On `develop` you can also activate the command-log layer. That will offer you the possibility to toggle this mode with SPC a L or M-m a L. All the key you will press will be recorded with their associated functions on a side buffer. You can then use the content of this buffer as a starting point of a reproduction guide.

Enable debug

To turn on the debug-on-error mode, what will give a backtrace of an error popping up at run-time, you can use SPC t D or M-m t D. This keybinding toggle the mode, so it can also be used to deactivate it.

After having enabled the debug-on-error mode, you can redo the action making the error to appear, then read the Reporting the backtrace section on how to get and report the problematic backtrace.

Enable debug at initialization

In order to get a backtrace of an error appearing at initialization time, you need to run emacs with the --debug-init flag, as in:

emacs --debug-init

The debug-on-error mode stays activated after the initialization, so no need to use SPC t D afterward to debug errors.

If load time is a problem

If part of the issue is the amount of time spacemacs takes to load, you can launch emacs with the command

emacs --debug-init --timed-requires

which will add a timer to all require and load statements. Any file that takes longer than 150ms (not configurable at the moment) to load will be logged in a buffer called *load-times*, which may help you narrow down the cause of the slow startup.

Get the backtrace

After having enabled the debug-on-error mode, if an error occurs its backtrace will be accessible in the *Backtrace* buffer. This buffer shows-up after an error. If it is not the case you can access it with SPC b b or M-m b b.

In order to get this buffer content, you can use M-m b Y, what will copy the buffers content in the system clipboard. You can paste it directly on Github issues between triple backquotes ```. If the content is too long, or for sharing it on gitter, it’s recommended to use a pastebin service.

Note: If you have the `github` layer enabled, you can use M-m g g b to directly send the content of the buffer to a gist and get back it’s URL. The URL is copied to the system clipboard so you can directly use it.

Dummy example of a good bug report

Note: Triple backquotes are not showing up because of some wiki parsing issues. Don’t forget to add them around the backtrace.

#### Description
Searching next/previous element in vim-mode with `n` and `N` are not working.

#### Reproduction guide
- Start Emacs
- Open the `.spacemacs` file with `SPC f e d`
- Search for the "dotspacemacs" with `/ dotspacemacs RET`
- Notice `n` and `N` are not working

#### System Info
- OS: gnu/linux
- Emacs: 24.5.1
- Spacemacs: 0.105.0
- Spacemacs branch: contrib/bepo (rev. cc4b324)
- Distribution: spacemacs
- Layers:

(asciidoc auto-completion better-defaults c-c++ clojure colors command-log deft dockerfile
              (elfeed :variables rmh-elfeed-org-files
                      (list "~/org/elfeed.org"))
              emacs-lisp emoji erc ess evil-cleverparens extra-langs finance git github haskell html ipython-notebook javascript latex markdown mu4e no-dots ocaml org pandoc python ranger restclient ruby semantic shell shell-scripts speed-reading
              (spell-checking :variables spell-checking-enable-auto-dictionary t)
              syntax-checking themes-megapack theming typography
              (version-control :variables version-control-diff-tool 'diff-hl)
              yaml)


#### Backtrace

Debugger entered--Lisp error: (error "Don't know where `evil-lisp-state-major-mode-map-prefix' is defined")
  signal(error ("Don't know where `evil-lisp-state-major-mode-map-prefix' is defined"))
  error("Don't know where `%s' is defined" evil-lisp-state-major-mode-map-prefix)
  find-function-search-for-symbol(evil-lisp-state-major-mode-map-prefix nil nil)
  find-function-noselect(evil-lisp-state-major-mode-map-prefix)
  find-definition-noselect(evil-lisp-state-major-mode-map-prefix nil)
  find-function-do-it(evil-lisp-state-major-mode-map-prefix nil switch-to-buffer)
  find-function(evil-lisp-state-major-mode-map-prefix)
  helm-descbinds-action:find-func(("SPC k" . evil-lisp-state-major-mode-map-prefix))
  helm-execute-selection-action-1()
  helm-execute-selection-action()