Package: emacs;
Reported by: Hendrik Tews <hendrik.tews <at> kernkonzept.com>
Date: Mon, 22 Jun 2020 23:47:02 UTC
Severity: normal
Found in version 26.3
Fixed in version 28.1
Done: Lars Ingebrigtsen <larsi <at> gnus.org>
Bug is archived. No further changes may be made.
Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):
From: Hendrik Tews <hendrik.tews <at> kernkonzept.com> To: bug-gnu-emacs <at> gnu.org Subject: 26.3; hash tables are not garbage collected Date: Tue, 23 Jun 2020 00:20:32 +0200
Hi,
I have the impression hash tables and their content are not
garbage collected when the hash table is not referenced any more.
Consider the following piece of elisp code:
(let (gc-start gc-state hash symbol result)
;; record gc statistics
(setq gc-start (garbage-collect))
;; create a hash and put an uninterned symbol into it
(setq hash (make-hash-table))
(setq symbol (make-symbol "x"))
(puthash symbol t hash)
;; take gc stats and record the differences of used symbols and used
;; vectors in result
(setq gc-state (garbage-collect))
(push (list 'sym1 (- (caddr (assoc 'symbols gc-state))
(caddr (assoc 'symbols gc-start))))
result)
(push (list 'vec1 (- (caddr (assoc 'vectors gc-state))
(caddr (assoc 'vectors gc-start))))
result)
;; make the symbol and the hash inaccessible
(setq symbol nil)
(setq hash nil)
;; take gc stats again and record the differences of used symbols
;; and used vectors in result
(setq gc-state (garbage-collect))
(push (list 'sym2 (- (caddr (assoc 'symbols gc-state))
(caddr (assoc 'symbols gc-start))))
result)
(push (list 'vec2 (- (caddr (assoc 'vectors gc-state))
(caddr (assoc 'vectors gc-start))))
result)
result)
With emacs -Q it returns ((vec2 5) (sym2 1) (vec1 5) (sym1 1)),
while I was expecting ((vec2 0) (sym2 0) ...).
What am I doing wrong that prevents the third call to
garbage-collect to garbage collect the hash and the uninterned
symbol?
Note that with inserting a clrhash before setting hash to nil,
the symbol gets collected, but the vectors won't. What is needed
to garbage collect a hash table?
Thanks,
Hendrik
text generated by report-emacs-bug:
In GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.20)
of 2020-05-17, modified by Debian built on x86-csail-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux bullseye/sid
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Configured using:
'configure --build x86_64-linux-gnu --prefix=/usr
--sharedstatedir=/var/lib --libexecdir=/usr/lib
--localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --enable-libsystemd --with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp
--with-sound=alsa --without-gconf --with-mailutils --build
x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib
--infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
--with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp
--with-sound=alsa --without-gconf --with-mailutils --with-x=yes
--with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
-fdebug-prefix-map=/build/emacs-mHAik2/emacs-26.3+1=. -fstack-protector-strong
-Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
-D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'
Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS GLIB
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS LIBSYSTEMD LCMS2
Important settings:
value of $LANG: en_US.UTF-8
value of $XMODIFIERS: @im=ibus
locale-coding-system: utf-8-unix
Major mode: Lisp Interaction
Minor modes in effect:
tooltip-mode: t
global-eldoc-mode: t
eldoc-mode: t
electric-indent-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
Load-path shadows:
None found.
Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils elec-pair time-date
mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors frame cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)
Memory information:
((conses 16 96516 5845)
(symbols 48 20785 1)
(miscs 40 45 96)
(strings 32 29163 1930)
(string-bytes 1 763910)
(vectors 16 14012)
(vector-slots 8 507754 6556)
(floats 8 49 68)
(intervals 56 268 0)
(buffers 992 12))
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