bug#27498: 25.2; Memory leak in M-x shell

[Ricardo Wurmus]

Emacs leaks memory as lines are printed in a shell buffer.  Here is a
recipe:

    emacs -Q
    M-x shell
    yes "This should not leak, but it does."

Observe the memory usage grow in a tool like “top”.  Once you decide
that Emacs has eaten enough memory, kill the shell buffer.  Note that
memory is not released.

This is a problem for me because I often compile software in shell
buffers (via “guix build”).  The compilation processes often print out
very large amounts of text and Emacs quickly eats up all memory on my
machine, freezing it.  I can only recover from this by killing Emacs
(which is terrible, because I live in Emacs).

This has not been a problem in Emacs 24.x; I’m also pretty confident
that this was no problem in version 25.1.

--
Ricardo

GPG: BCA6 89B6 3655 3801 C3C6  2150 197A 5888 235F ACAC
https://elephly.net




In GNU Emacs 25.2.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.22.12)
 of 2017-04-24 built on localhost
Windowing system distributor 'The X.Org Foundation', version 11.0.11903000
Configured using:
 'configure
 CONFIG_SHELL=/gnu/store/k7029k5va68lkapbzcycdzj7m5bjb4b8-bash-4.4.12/bin/bash
 SHELL=/gnu/store/k7029k5va68lkapbzcycdzj7m5bjb4b8-bash-4.4.12/bin/bash
 --prefix=/gnu/store/q3kvsn12x99fpiw08a2jgw9h6biky907-emacs-25.2
 --enable-fast-install'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS GSETTINGS NOTIFY ACL GNUTLS
LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: mu4e:compose

Minor modes in effect:
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  async-bytecomp-package-mode: t
  mml-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-ring-mode: t
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  erc-fill-mode: t
  erc-stamp-mode: t
  erc-autojoin-mode: t
  erc-autoaway-mode: t
  erc-smiley-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  typo-mode: t
  TeX-PDF-mode: t
  guide-key-mode: t
  diff-auto-refine-mode: t
  pdf-occur-global-minor-mode: t
  savehist-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  delete-selection-mode: t
  desktop-save-mode: t
  display-time-mode: t
  projectile-global-mode: t
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  global-guix-prettify-mode: t
  guix-prettify-mode: t
  shell-switcher-mode: t
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  show-paren-mode: t
  save-place-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  global-prettify-symbols-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
  column-number-mode: t
  line-number-mode: t
  auto-fill-function: message-do-auto-fill
  transient-mark-mode: t
  abbrev-mode: t

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Memory information:
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