GNU bug report logs -
#54990
Byte compiler bug
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Reported by: Alan Mackenzie <acm <at> muc.de>
Date: Sun, 17 Apr 2022 12:59:02 UTC
Severity: normal
Done: Alan Mackenzie <acm <at> muc.de>
Bug is archived. No further changes may be made.
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[Message part 1 (text/plain, inline)]
Your message dated Mon, 18 Apr 2022 10:48:43 +0000
with message-id <Yl1CCxxxwpCt3nIJ <at> ACM>
and subject line Re: bug#54990: Byte compiler bug
has caused the debbugs.gnu.org bug report #54990,
regarding Byte compiler bug
to be marked as done.
(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)
--
54990: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=54990
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems
[Message part 2 (message/rfc822, inline)]
Hello, Emacs.
In up to date master branch:
(i) emacs -Q
(ii) Enter the following into buffer *scratch*:
(defun E+->E@+ (elt op)
(cond
((eq op '+) (setcar elt '*))
((eq op '+\?) (setcar elt '*\?))))
(defconst foo-elt '(+\? . "foo"))
(E+->E@+ foo-elt '+\?)
.
(iii) With point in the defun, M-x compile-defun.
(iv) Evaluate the defconst.
(v) Evaluate the E+->E@+ form.
(vi) M-: foo-elt. It's value is unchanged from its declaration. It
should have been changed to (*\? . "foo"). This is a bug.
(vii) M-x disassemble RET E+->E@+. Instead of working, this gives the
error message:
Optimizer error: missed tags (((TAG 2) TAG 4) ((TAG 1) TAG 3))
. This is a bug.
(viii) (Optional) Evaluate the defun form with C-M-x, and evaluate the
E+->E@+ form. M-: foo-elt. This shows the expected value,
(*? . "foo").
At a guess, the symbols with the \? in their names have something to do
with the bug.
Here is my configuration:
In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
3.24.31, cairo version 1.16.0)
of 2022-04-17 built on ACM
Repository revision: 2136db067f4292d84553ebfddab30d88b862262e
Repository branch: master
System Description: Gentoo/Linux
Configured using:
'configure --with-gif=no --with-tiff=no --with-gpm
--with-native-compilation'
Configured features:
ACL CAIRO DBUS FREETYPE GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG
SECCOMP SOUND SQLITE3 THREADS TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM XPM
GTK3 ZLIB
--
Alan Mackenzie (Nuremberg, Germany).
[Message part 3 (message/rfc822, inline)]
Hello, Mattias.
On Sun, Apr 17, 2022 at 16:32:53 +0200, Mattias Engdegård wrote:
> This is related to symbol positioning so Alan should be well-placed to
> debug it. (The symbol names are irrelevant.)
I'd got just as far as identifying the merge of
scratch/correct-warning-pos as the first version containing the bug.
> It's `compile-defun` that is broken; the constant vector of the
> resulting bytecode contains symbols with position as hash table keys
> for a switch operation. Compare the bytecode object with that from
> `byte-compile` which works correctly:
Thank you for this observation. It was _exceptionally_ helpful.
> (defun tata (x)
> (cond
> ((eq x 'a) 'toto)
> ((eq x 'b) 'titi)))
> (byte-compile 'tata)
> =>
> #[257 "..." [#s(hash-table size 2 test eq rehash-size 1.5 rehash-threshold 0.8125 purecopy t data (a 6 b 8)) toto titi nil] 3 "..."]
> ;; if using `compile-defun` on `tata`:
> (symbol-function 'tata)
> #[257 "..." [#s(hash-table size 2 test eq rehash-size 1.5 rehash-threshold 0.8125 purecopy t data (#<symbol a at 293> 6 #<symbol b at 314> 8)) toto titi nil] 3 "..."]
I've committed a fix, which I'm pretty sure works, so I'm closing the bug
with this post. Thanks again for the help!
--
Alan Mackenzie (Nuremberg, Germany).
This bug report was last modified 3 years and 81 days ago.
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