Ticket #4253 (new defect)
Interference of injected subshell commands output with e.g. read in .zshrc causing 10s startup delay
Reported by: | marlonrichert | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | Future Releases |
Component: | mc-core | Version: | 4.8.26 |
Keywords: | subshell common.c init_subshell zsh .zshrc | Cc: | baltazar.bz@… |
Blocked By: | Blocking: | ||
Branch state: | no branch | Votes for changeset: |
Description
Steps to reproduce
$ cd $(mktemp -d); exec env -i HOME=$PWD TERM=$TERM zsh -f % print -r "typeset -F SECONDS print -nr \$'\e[6n' # We query the terminal for info. IFS=\$'\e[;' read -Asd R -- reply # We read the terminal's reply. print \$SECONDS " > .zshrc % exec zsh # Starting zsh is still instantaneous. 0.0557880000 % SECONDS=0; mc; print $SECONDS # Starting mc is now really slow. 11.5728380000 %
The problem is here: https://github.com/MidnightCommander/mc/blob/a88a626e76139259e5b6fc0db39045f051e243dd/src/subshell/common.c#L1378
You print commands to the shell as if it were user input or terminal input. This interferes with the read statement in the .zshrc file: The terminal's reply is now buried inside the characters you are printing. As a result, the read statement hangs until it times out and most of the commands you print don't get executed.
Expected behavior
Don't print to the shell. If you want to execute commands, just pass them straight to Zsh by using the -c flag. See https://zsh.sourceforge.io/Doc/Release/Invocation.html#Invocation-2
mc debug info
% LC_MESSAGES=C mc -F Home directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX Profile root directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX [System data] Config directory: /usr/local/Cellar/midnight-commander/4.8.26/etc/mc/ Data directory: /usr/local/Cellar/midnight-commander/4.8.26/share/mc/ File extension handlers: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/ext.d/ VFS plugins and scripts: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/ extfs.d: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/extfs.d/ fish: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/fish/ [User data] Config directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.config/mc/ Data directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/ skins: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/skins/ extfs.d: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/extfs.d/ fish: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/fish/ mcedit macros: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/mc.macros mcedit external macros: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/mcedit/macros.d/macro.* Cache directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.cache/mc/ % LC_MESSAGES=C mc -F mc --configure-options Home directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX Profile root directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX [System data] Config directory: /usr/local/Cellar/midnight-commander/4.8.26/etc/mc/ Data directory: /usr/local/Cellar/midnight-commander/4.8.26/share/mc/ File extension handlers: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/ext.d/ VFS plugins and scripts: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/ extfs.d: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/extfs.d/ fish: /usr/local/Cellar/midnight-commander/4.8.26/libexec/mc/fish/ [User data] Config directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.config/mc/ Data directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/ skins: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/skins/ extfs.d: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/extfs.d/ fish: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/fish/ mcedit macros: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/mc.macros mcedit external macros: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.local/share/mc/mcedit/macros.d/macro.* Cache directory: /private/var/folders/24/37_vm48s2tz9bhmj1rzffvl40000gn/T/tmp.J1v4nVJX/.cache/mc/ '--disable-debug' '--disable-dependency-tracking' '--disable-silent-rules' '--prefix=/usr/local/Cellar/midnight-commander/4.8.26' '--without-x' '--with-screen=slang' '--enable-vfs-sftp' 'CC=clang' 'PKG_CONFIG_PATH=/usr/local/opt/libffi/lib/pkgconfig:/usr/local/opt/pcre/lib/pkgconfig:/usr/local/opt/openssl@1.1/lib/pkgconfig:/usr/local/opt/readline/lib/pkgconfig:/usr/local/opt/sqlite/lib/pkgconfig:/usr/local/opt/tcl-tk/lib/pkgconfig:/usr/local/opt/xz/lib/pkgconfig:/usr/local/opt/python@3.9/lib/pkgconfig:/usr/local/opt/glib/lib/pkgconfig:/usr/local/opt/libssh2/lib/pkgconfig:/usr/local/opt/libpng/lib/pkgconfig:/usr/local/opt/s-lang/lib/pkgconfig' 'PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig:/usr/local/Homebrew/Library/Homebrew/os/mac/pkgconfig/11' % mc -V GNU Midnight Commander 4.8.26 Built with GLib 2.66.4 Built with S-Lang 2.3.2 with terminfo database With builtin Editor With subshell support as default With support for background operations With mouse support on xterm With internationalization support With multiple codepages support Virtual File Systems: cpiofs, tarfs, sfs, extfs, ftpfs, sftpfs, fish Data types: char: 8; int: 32; long: 64; void *: 64; size_t: 64; off_t: 64;
Change History
comment:1 Changed 4 years ago by marlonrichert
- Keywords zsh .zshrc added
- Summary changed from `mc` interferes with `read` in `.zshrc` causing 10 second `mc` startup delay to `subshell/common.c` interferes with `read` in `.zshrc` causing 10 second `mc` startup delay
comment:2 Changed 4 years ago by marlonrichert
- Keywords init_subshell added
- Summary changed from `subshell/common.c` interferes with `read` in `.zshrc` causing 10 second `mc` startup delay to `subshell/common.c/init_subshell` interferes with `read` in `.zshrc` causing 10 second `mc` startup delay
comment:5 Changed 4 years ago by ossi
no. there, a "naturally slow" startup of the shell is just exposed by mc. here, we're talking about active interference with the script's own bi-directional communication with the tty.
this problem could be avoided by wrapping the invoked init script into an own script that outputs a readiness indicator for synchronization purposes, like "<< MC subshell READY! >>>".
any one-time initialization commands could be injected this way as well (though the traditional method would still have be used for shells with no init file support, but the paths are shell-specific anyway).
generally, i'd recommend doing as much of the protocol as possible over the auxiliary pipes which we now have anyway.
comment:6 Changed 4 years ago by marlonrichert
- Summary changed from `subshell/common.c/init_subshell` interferes with `read` in `.zshrc` causing 10 second `mc` startup delay to subshell/common.c/init_subshell interferes with read in .zshrc causing 10 second mc startup delay
comment:7 Changed 3 years ago by ossi
speaking of using a wrapper script, that should be seen in the context of #4254.
comment:8 Changed 3 months ago by zaytsev
- Summary changed from subshell/common.c/init_subshell interferes with read in .zshrc causing 10 second mc startup delay to Interference of injected subshell commands output with e.g. read in .zshrc causing 10s startup delay
I wonder if better own communication isolation would also solve problems with slow start on FreeBSD (#4548).