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Re: Read builtin -e (readline) oddities


From: Eduardo A . Bustamante López
Subject: Re: Read builtin -e (readline) oddities
Date: Mon, 19 Jun 2017 09:57:55 -0500
User-agent: NeoMutt/20170113 (1.7.2)

On Mon, Jun 19, 2017 at 10:08:30AM -0400, Chet Ramey wrote:
[...]
> I can't reproduce this.  I suspect one of your startup files is somehow
> being read and setting PATH. It may also be an interaction with the
> command-not-found hook.

Hm, I can still reproduce it under Debian 9, using the `devel' branch, and I'm
sure no startup files are being sourced.

  address@hidden:~/src/gnu/bash-builds/devel$ ./bash --norc --noprofile
  bash-4.4$ declare -p command-not-found
  bash: declare: command-not-found: not found
  bash-4.4$ 
  GNU bash, version 4.4.12(3)-maint (x86_64-unknown-linux-gnu)
  bash-4.4$ PATH= read -e
  
  bash: vim: No such file or directory
  
  echo this is vim
  this is vim

I then patched bash like this:

  address@hidden:~/src/gnu/bash$ git diff -- execute_cmd.c
  diff --git a/execute_cmd.c b/execute_cmd.c
  index 0183a105..50f4e2f0 100644
  --- a/execute_cmd.c
  +++ b/execute_cmd.c
  @@ -5550,6 +5550,7 @@ shell_execve (command, args, env)
     char sample[HASH_BANG_BUFSIZ];
     int sample_len;
   
  +  if (strlen(get_string_value ("PATH")) > 0) abort();
     SETOSTYPE (0);               /* Some systems use for USG/POSIX semantics */
     execve (command, args, env);
     i = errno;                   /* error from execve() */

And I got (the first `\C-x \C-e' gets to shell_execve, but PATH is empty):

  address@hidden:~/src/gnu/bash-builds/devel$ ./bash --norc --noprofile
  bash-4.4$ ulimit -c unlimited
  bash-4.4$ 
  GNU bash, version 4.4.12(9)-maint (x86_64-unknown-linux-gnu)
  bash-4.4$ PATH= read -e
  
  bash: vim: No such file or directory
  
  Aborted (core dumped)
  
  Core was generated by `./bash --norc --noprofile'.
  Program terminated with signal SIGABRT, Aborted.
  #0  __GI_raise (address@hidden) at ../sysdeps/unix/sysv/linux/raise.c:51
  51      ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
  (gdb) bt
  #0  __GI_raise (address@hidden) at ../sysdeps/unix/sysv/linux/raise.c:51
  #1  0x00007f30b14c93fa in __GI_abort () at abort.c:89
  #2  0x000055a0df6527c4 in shell_execve (command=0x55a0e0a21020 
"/usr/bin/vim", args=0x55a0e0a64610, env=0x55a0e0a207f0) at 
../../bash/execute_cmd.c:5553
  #3  0x000055a0df6525b1 in execute_disk_command (words=0x55a0e0a63c20, 
redirects=0x0, command_line=0x55a0e0a20f60 "vim /tmp/bash-fc.HTeaRz", 
pipe_in=-1, pipe_out=-1, async=0, 
      fds_to_close=0x55a0e0a42d80, cmdflags=0) at ../../bash/execute_cmd.c:5348
  #4  0x000055a0df650d4f in execute_simple_command 
(simple_command=0x55a0e0a62780, pipe_in=-1, pipe_out=-1, async=0, 
fds_to_close=0x55a0e0a42d80) at ../../bash/execute_cmd.c:4466
  #5  0x000055a0df64a465 in execute_command_internal (command=0x55a0e0a20e80, 
asynchronous=0, pipe_in=-1, pipe_out=-1, fds_to_close=0x55a0e0a42d80) at 
../../bash/execute_cmd.c:811
  #6  0x000055a0df6ad6a8 in parse_and_execute (string=0x55a0e0a61b10 "vim 
/tmp/bash-fc.HTeaRz", from_file=0x55a0df71cecd "fc", flags=4) at 
../../../bash/builtins/evalstring.c:430
  #7  0x000055a0df6aee93 in fc_builtin (list=0x0) at 
../../../bash/builtins/../../../bash/builtins/fc.def:438
  #8  0x000055a0df6511cb in execute_builtin (builtin=0x55a0df6ae4ae 
<fc_builtin>, words=0x55a0e0a625d0, flags=0, subshell=0) at 
../../bash/execute_cmd.c:4609
  #9  0x000055a0df6520a7 in execute_builtin_or_function (words=0x55a0e0a625d0, 
builtin=0x55a0df6ae4ae <fc_builtin>, var=0x0, redirects=0x0, 
fds_to_close=0x55a0e0a63df0, flags=0)
      at ../../bash/execute_cmd.c:5107
  #10 0x000055a0df650ad1 in execute_simple_command 
(simple_command=0x55a0e0a62540, pipe_in=-1, pipe_out=-1, async=0, 
fds_to_close=0x55a0e0a63df0) at ../../bash/execute_cmd.c:4395
  #11 0x000055a0df64a465 in execute_command_internal (command=0x55a0e0a20400, 
asynchronous=0, pipe_in=-1, pipe_out=-1, fds_to_close=0x55a0e0a63df0) at 
../../bash/execute_cmd.c:811
  #12 0x000055a0df6ad6a8 in parse_and_execute (string=0x55a0e0a613b0 "fc -e 
\"${VISUAL:-${EDITOR:-emacs}}\"", from_file=0x55a0df70ccd5 "C-xC-e", flags=4)
      at ../../../bash/builtins/evalstring.c:430
  #13 0x000055a0df696203 in edit_and_execute_command (count=1, c=5, 
editing_mode=1, edit_command=0x55a0df70cd10 "fc -e 
\"${VISUAL:-${EDITOR:-emacs}}\"") at ../../bash/bashline.c:977
  #14 0x000055a0df6962f0 in emacs_edit_and_execute_command (count=1, c=5) at 
../../bash/bashline.c:1013
  #15 0x000055a0df6dccd5 in _rl_dispatch_subseq (key=5, map=0x55a0df9461a0 
<emacs_ctlx_keymap>, got_subseq=0) at 
../../../../bash/lib/readline/readline.c:851
  #16 0x000055a0df6dd19a in _rl_dispatch_subseq (key=24, map=0x55a0df944160 
<emacs_standard_keymap>, got_subseq=0) at 
../../../../bash/lib/readline/readline.c:985
  #17 0x000055a0df6dca4c in _rl_dispatch (key=-1320386609, map=0x55a0df944160 
<emacs_standard_keymap>) at ../../../../bash/lib/readline/readline.c:797
  #18 0x000055a0df6dc6d4 in readline_internal_char () at 
../../../../bash/lib/readline/readline.c:629
  #19 0x000055a0df6dc72c in readline_internal_charloop () at 
../../../../bash/lib/readline/readline.c:656
  #20 0x000055a0df6dc750 in readline_internal () at 
../../../../bash/lib/readline/readline.c:670
  #21 0x000055a0df6dc16d in readline (prompt=0x55a0df71d63c "") at 
../../../../bash/lib/readline/readline.c:374
  #22 0x000055a0df6b6407 in edit_line (p=0x55a0df71d63c "", itext=0x0) at 
../../../bash/builtins/../../../bash/builtins/read.def:1095
  #23 0x000055a0df6b5243 in read_builtin (list=0x0) at 
../../../bash/builtins/../../../bash/builtins/read.def:559
  #24 0x000055a0df6511cb in execute_builtin (builtin=0x55a0df6b44f9 
<read_builtin>, words=0x55a0e0a60ed0, flags=0, subshell=0) at 
../../bash/execute_cmd.c:4609
  #25 0x000055a0df6520a7 in execute_builtin_or_function (words=0x55a0e0a60ed0, 
builtin=0x55a0df6b44f9 <read_builtin>, var=0x0, redirects=0x0, 
fds_to_close=0x55a0e0a61070, flags=0)
      at ../../bash/execute_cmd.c:5107
  #26 0x000055a0df650ad1 in execute_simple_command 
(simple_command=0x55a0e0a60df0, pipe_in=-1, pipe_out=-1, async=0, 
fds_to_close=0x55a0e0a61070) at ../../bash/execute_cmd.c:4395
  #27 0x000055a0df64a465 in execute_command_internal (command=0x55a0e0a42ba0, 
asynchronous=0, pipe_in=-1, pipe_out=-1, fds_to_close=0x55a0e0a61070) at 
../../bash/execute_cmd.c:811
  #28 0x000055a0df6499c1 in execute_command (command=0x55a0e0a42ba0) at 
../../bash/execute_cmd.c:393
  #29 0x000055a0df633a2a in reader_loop () at ../../bash/eval.c:172
  #30 0x000055a0df631677 in main (argc=3, argv=0x7fff33cecb28, 
env=0x7fff33cecb48) at ../../bash/shell.c:794

  (gdb) frame
  #2  0x000055a0df6527c4 in shell_execve (command=0x55a0e0a21020 
"/usr/bin/vim", args=0x55a0e0a64610, env=0x55a0e0a207f0) at 
../../bash/execute_cmd.c:5553
  5553      if (strlen(get_string_value ("PATH")) > 0) abort();
  (gdb) p env[30]
  $15 = 0x55a0e0a21140 
"PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games"
  (gdb) p env[5]
  $16 = 0x55a0e0a61460 "EDITOR=vim"


This works fine though:

  address@hidden:~/src/gnu/bash-builds/devel$ ./bash --norc --noprofile
  bash-4.4$ export PATH=
  bash-4.4$ read -e
  
  bash: vim: No such file or directory
  
  bash: vim: No such file or directory
  
  bash: vim: No such file or directory
  ^C

So it seems that the problem is that the tempenv is reset for the second
execution of the `fc' builtin.



And in the case of getting the extra `;'s in the history, it would seem it adds
one per failed execve:

  bash-4.4$ history -c
  bash-4.4$ export PATH=
  bash-4.4$ read -e
  
  bash: vim: No such file or directory
  
  bash: vim: No such file or directory
  
  bash: vim: No such file or directory
  
  bash: vim: No such file or directory
  
  bash: vim: No such file or directory
  bash-4.4$ history
      1  export PATH=
      2  read -e; ; ; ; ; 
      3  history

-- 
Eduardo Bustamante
https://dualbus.me/



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