bug#48383: [native-compile] Debugging external package powerline.el

bug#48383: [native-compile] Debugging external package powerline.el

[Arash Esbati]

Hi all,

I have successfully built Emacs with native-compile support on Win10[1]
and it works fine -- many thanks for this.

I've also installed powerline package from MELPA and Emacs fails to
compile the package with this error:

    x:/pathto/.emacs.d/elpa/powerline-20210428.1229/powerline.el:
    Error: List contains a loop ("22", . #0)
    Compilation finished.

How can I get more info about the error from the compiler?  Currently
Emacs tries to compile the package each time it starts (and fails) and
that makes the start slower.

TIA for any hint.

Best, Arash

Footnotes:
[1]  emacs-repository-version is 8b7495a722a57071cb2a978665f95f8227db2863

bug#48383: [native-compile] Debugging external package powerline.el

[Andrea Corallo via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Arash Esbati <arash@gnu.org> writes:

> Hi all,
>
> I have successfully built Emacs with native-compile support on Win10[1]
> and it works fine -- many thanks for this.
>
> I've also installed powerline package from MELPA and Emacs fails to
> compile the package with this error:
>
>     x:/pathto/.emacs.d/elpa/powerline-20210428.1229/powerline.el:
>     Error: List contains a loop ("22", . #0)
>     Compilation finished.
>
> How can I get more info about the error from the compiler?  Currently
> Emacs tries to compile the package each time it starts (and fails) and
> that makes the start slower.
>
> TIA for any hint.
>
> Best, Arash
>
> Footnotes:
> [1]  emacs-repository-version is 8b7495a722a57071cb2a978665f95f8227db2863

Hi Arash,

if the compiler crashes I guess the next step is to debug it.  But
before doing that would be nice to isolate what's the function that is
causing the issue and create a reproducer.

Thanks

  Andrea

PS you can work around the issue of the startup adding powerline.el to
`native-comp-deferred-compilation-deny-list'.

bug#48383: [native-compile] Debugging external package powerline.el

[Arash Esbati]

Andrea Corallo <akrl@sdf.org> writes:

> if the compiler crashes I guess the next step is to debug it.

Thanks for your response.  In this case, the compiler doesn't crash.

> But before doing that would be nice to isolate what's the function
> that is causing the issue and create a reproducer.

From the discussion here[1], the problem seems to be the last line in
this function provided by powerline.el[2]:

    (defun pl/pattern (lst)
      "Turn LST into an infinite pattern."
      (when lst
        (let ((pattern (cl-copy-list lst)))
          (setcdr (last pattern) pattern)))) ;; <== Problematic form

Not being an Emacs issue, my question was if the native compiler could
be more verbose about the error.

> PS you can work around the issue of the startup adding powerline.el to
> `native-comp-deferred-compilation-deny-list'.

Thanks, this is what I did for now.

Best, Arash

Footnotes:
[1]  https://github.com/milkypostman/powerline/issues/187

[2]  https://github.com/milkypostman/powerline/issues/187#issuecomment-836582479