bug#16416: 24.3; [SMIE] Assertion failure in smie-prec2->grammar

bug#16416: 24.3; [SMIE] Assertion failure in smie-prec2->grammar

[Raphaël Cauderlier]

Hello,

I started emacs with emacs -Q and evaled the following file with
load-file:

-----
(require 'smie)
(smie-prec2->grammar (smie-bnf->prec2 '((name) (l ("a" name)))))
-----

This raised the following error message:

(cl-assertion-failed (numberp (car cons)))

where I expected a SMIE grammar to be returned without error message.
The inner function smie-bnf->prec2 doesn't fail and the documentation
string for the outter function smie-prec2->grammar indicates that it's
argument could be a value returned by smie-bnf->prec2:

-----
smie-prec2->grammar is a compiled Lisp function in `smie.el'.

(smie-prec2->grammar PREC2)

Take a 2D precedence table and turn it into an alist of precedence levels.
PREC2 is a table as returned by `smie-precs->prec2' or
`smie-bnf->prec2'.
-----

I hope I gave you enough information to reproduce this issue.  I'm not
very familiar with the Lisp Debugger so I don't know how to get a
backtrace from a cl-assertion-failed.

Have a nice day!

-- 
Raphaël Cauderlier



In GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.8.6)
 of 2013-12-22 on brahms, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11204000
System Description:	Debian GNU/Linux testing (jessie)

Configured using:
 `configure '--build' 'x86_64-linux-gnu' '--build' 'x86_64-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 '--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.3/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/x86_64-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=gtk3' '--with-toolkit-scroll-bars'
 'build_alias=x86_64-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall'
 'LDFLAGS=-Wl,-z,relro' 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LANG: fr_FR.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x l o a d - f i l e <return> s m i e - b u g . l 
<backspace> e l <return> M-x r e p o r t - e m a c 
s - b u g <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading /home/harry/test/smie-bug.el (source)...
smie-prec2->grammar: Assertion failed: (numberp (car cons))

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils smie time-date tooltip ediff-hook vc-hooks
lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image regexp-opt
fringe tabulated-list newcomment lisp-mode register page menu-bar
rfn-eshadow timer select scroll-bar mouse jit-lock font-lock syntax
facemenu font-core frame cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese hebrew greek romanian slovak
czech european ethiopic indian cyrillic chinese case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
make-network-process dbusbind dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

bug#16416: 24.3; [SMIE] Assertion failure in smie-prec2->grammar

[Stefan Monnier]

> (smie-prec2->grammar (smie-bnf->prec2 '((name) (l ("a" name)))))
> This raised the following error message:
> (cl-assertion-failed (numberp (car cons)))

Hmm..indeed.  The assertion can be removed, but then we bump into
another signal.  The problem is that the grammar is simply "too
trivial" and smie.el seems to bump into invalid assumptions in
that case.  As soon as you add some other terminal to the "l" rule, or
the "name" rule, or you use "l" somewhere, the problem disappears.

Intuitively this problem might manifest itself in a more realistic
grammar, yet I don't quite see in which case, and for that reason
I don't really see yet what would be the right fix.  I'm tempted to
think that the problem is partly to blame on smie-bnf->prec2 which
generates a prec2 table where "a" is missing (except for the side info
of :smie-open/close-alist).


        Stefan

bug#16416: 24.3; [SMIE] Assertion failure in smie-prec2->grammar

[Raphael Cauderlier]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> (smie-prec2->grammar (smie-bnf->prec2 '((name) (l ("a" name)))))
>> This raised the following error message:
>> (cl-assertion-failed (numberp (car cons)))
>
> Hmm..indeed.  The assertion can be removed, but then we bump into
> another signal.  The problem is that the grammar is simply "too
> trivial" and smie.el seems to bump into invalid assumptions in
> that case.  As soon as you add some other terminal to the "l" rule, or
> the "name" rule, or you use "l" somewhere, the problem disappears.
>
> Intuitively this problem might manifest itself in a more realistic
> grammar,

I don't know if you would call it realistic but I actually got it with
the following grammar:

  (smie-prec2->grammar
   (smie-bnf->prec2
    '((id)
      (prelude ("#NAME" id))
      (line ("#IMPORT" id)
            (term ".")
            (term ":=" term ".")
            (rule)
            (rule ".")
            ("#ASSERT" term "=~" term "."))
      (rule ("[" context "]" term "-->" term))
      (decl (id ":" term))
      (context (decl "," context)
               (decl))
      (term (id)
            ("{" id "}")
            (decl)
            ("_")
            (term "->" term)
            (decl "=>" term)))
    '((assoc ":")
      (assoc "->" "=>"))))

which I find a bit more complicated than the example grammar given in
the manual section `SMIE Grammar'.

I wrote this from Dedukti BNF grammar.  Dedukti
(https://www.rocq.inria.fr/deducteam/Dedukti/index.html) is a simple
language for which I am writing a major mode
(https://github.com/rafoo/dedukti-mode/blob/master/dedukti-mode.el).

I then minimized the example before reporting, keeping only the `id'
empty rule and the first `line' rule.

> As soon as you add some other terminal to the "l" rule, or
> the "name" rule, or you use "l" somewhere, the problem disappears.

Thank you for your suggestion, I added "\n" at the end of, the first
`line' rule and the problem is solved for me; I can continue to play
with SMIE :)

> yet I don't quite see in which case, and for that reason
> I don't really see yet what would be the right fix.  I'm tempted to
> think that the problem is partly to blame on smie-bnf->prec2 which
> generates a prec2 table where "a" is missing (except for the side info
> of :smie-open/close-alist).

Thank you for your investigation and thank you for SMIE; I am sure it
will help me a lot improving my major mode indentation!

-- 
Raphaël Cauderlier

bug#16416: 24.3; [SMIE] Assertion failure in smie-prec2->grammar

[Lars Ingebrigtsen]

cauderlier@crans.org (Raphaël Cauderlier) writes:

> I started emacs with emacs -Q and evaled the following file with
> load-file:
>
> -----
> (require 'smie)
> (smie-prec2->grammar (smie-bnf->prec2 '((name) (l ("a" name)))))
> -----
>
> This raised the following error message:
>
> (cl-assertion-failed (numberp (car cons)))

(I'm going through old bug reports.)

In more recent versions of Emacs, the `smie-prec2->grammar' call returns
nil, so it seems like this bug has been fixed.  (And if I interpret what
Stefan said at the time correctly, that's the right value.)

So I'm closing this bug report.  If there's something more to be worked
on here, please respond to the debbugs address and we'll reopen.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no