bug#29154: 25.3; Eshell: Pipes seem to hang or corrupt data when text chunk is large (>10k lines)

[Pierre Neidhardt]

- emacs -Q
- M-x eshell

        ~ $ time cat /usr/share/dict/words | wc -l
        234937
        12.005 secs
        ~ $ time cat /usr/share/dict/words | wc -l
        234937
        12.010 secs
        ~ $ time cat /usr/share/dict/words | wc -l
        234937
        11.321 secs
        ~ $ time cat /usr/share/dict/words | wc -l
        234937
        11.861 secs
        ~ $ time cat /usr/share/dict/words | wc -l
        188508
        3.734 secs
        ~ $ 

Notice in the last case that the output is wrong.

Sometimes the above command seeminly never terminates, or maybe it's
just taking too long for my patience.

Because of its randomness, it's hard to reproduce.



In GNU Emacs 25.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.16)
 of 2017-11-05 built on dhiov23k
Windowing system distributor 'The X.Org Foundation', version 11.0.11905000
System Description:     Gentoo Base System release 2.4.1

Configured using:
 'configure --prefix=/usr --build=x86_64-pc-linux-gnu
 --host=x86_64-pc-linux-gnu --mandir=/usr/share/man
 --infodir=/usr/share/info --datadir=/usr/share --sysconfdir=/etc
 --localstatedir=/var/lib --disable-dependency-tracking
 --disable-silent-rules --docdir=/usr/share/doc/emacs-25.3
 --htmldir=/usr/share/doc/emacs-25.3/html --libdir=/usr/lib64
 --program-suffix=-emacs-25 --infodir=/usr/share/info/emacs-25
 --localstatedir=/var
 --enable-locallisppath=/etc/emacs:/usr/share/emacs/site-lisp
 --with-gameuser=:gamestat --without-compress-install
 --with-file-notification=inotify --enable-acl --without-dbus
 --without-modules --without-gpm --without-hesiod --without-kerberos
 --without-kerberos5 --with-xml2 --without-selinux --with-gnutls
 --without-wide-int --with-zlib --with-sound=alsa --with-x --without-ns
 --without-gconf --without-gsettings --without-toolkit-scroll-bars
 --with-gif --with-jpeg --with-png --with-rsvg --with-tiff --with-xpm
 --with-imagemagick --with-xft --without-cairo --without-libotf
 --without-m17n-flt --with-x-toolkit=gtk3 --without-xwidgets
 GENTOO_PACKAGE=app-editors/emacs-25.3 'CFLAGS=-march=ivybridge -O2
 -pipe' CPPFLAGS= 'LDFLAGS=-Wl,-O1 -Wl,--as-needed''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND NOTIFY ACL GNUTLS LIBXML2
FREETYPE XFT ZLIB GTK3 X11

Important settings:
  value of $LANG: en_US.utf8
  locale-coding-system: utf-8-unix