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From: Jeff King <peff@peff.net>
To: Brandon Williams <bmwill@google.com>
Cc: Jonathan Nieder <jrnieder@gmail.com>,
	Eric Rannaud <eric.rannaud@gmail.com>,
	git@vger.kernel.org,
	Johannes Schindelin <johannes.schindelin@gmx.de>,
	Jeremy Serror <jeremy.serror@gmail.com>
Subject: Re: git rebase regression: cannot pass a shell expression directly to --exec
Date: Tue, 16 May 2017 13:23:07 -0400	[thread overview]
Message-ID: <20170516172307.36hyshwypomlsubx@sigill.intra.peff.net> (raw)
In-Reply-To: <20170516171540.GG79147@google.com>

On Tue, May 16, 2017 at 10:15:40AM -0700, Brandon Williams wrote:

> > > > So I was thinking something like the patch below, though I guess
> > > > technically you could look for BASH_FUNC_$argv[0]%%, which seems to be
> > > > bash's magic variable name. I hate to get too intimate with those
> > > > details, though.
> 
> One concern with that is what about all other shells that are not BASH?
> I'm sure they use a different env var for storing functions so we may
> need to handle other shell's too? That is assuming we want to keep the
> old behavior.

Most other shells don't do function-exporting at all. Certainly dash and
most traditional bourne shells don't. I wouldn't be surprised if zsh
does. But yeah, we'd have to support them one by one (and possibly
variants across different versions of each shell). Workable, but gross.

> > When execvp(foo) falls back on ENOEXEC, it is not running "sh -c foo".
> > It is actually running "sh foo" to run the script contents. So it's
> > about letting you do:
> > 
> >   echo "no shebang line" >script
> >   chmod +x script
> >   ./script
> > 
> > And nothing to do with shell builtins.
> 
> That's correct, and is the exact behavior I was trying to mimic with the
> changes to run_command.
>   1. try executing the command.
>   2. if it fails with ENOEXEC then attempt to execute it with a shell

I think the logic here would be more like:

  1. During prepare_shell_cmd(), even if we optimize out the shell call,
     still prepare a fallback argv (since we can't allocate memory
     post-fork).

  2. In the forked child, if we get ENOENT from exec and cmd->use_shell
     is set, then exec the fallback shell argv instead. Propagate its
     results, even if it's 127.

That still means we'd prefer a $PATH copy of a command to its shell
builtin variant, but that can't be helped (and I kind of doubt anybody
would care too much).

-Peff

  reply	other threads:[~2017-05-16 17:23 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-15 18:08 git rebase regression: cannot pass a shell expression directly to --exec Eric Rannaud
2017-05-16  3:25 ` Jeff King
2017-05-16  3:37   ` Jeff King
2017-05-16 16:41     ` Jonathan Nieder
2017-05-16 16:47       ` Jeff King
2017-05-16 17:11         ` Eric Rannaud
2017-05-16 17:15         ` Brandon Williams
2017-05-16 17:23           ` Jeff King [this message]
2017-05-16 17:30             ` Brandon Williams
2017-05-16 19:14             ` Linus Torvalds
2017-05-16 19:35               ` [TANGENT] run-command: use vfork instead of fork Eric Wong
2017-05-16 20:47                 ` Linus Torvalds
2017-05-16 21:11                   ` Brandon Williams
2017-05-16 20:12               ` git rebase regression: cannot pass a shell expression directly to --exec Johannes Schindelin
2017-05-16 20:27                 ` Linus Torvalds
2017-05-16 17:37         ` Jonathan Nieder
2017-05-16  3:40   ` Junio C Hamano
2017-05-16  3:53     ` Jeff King
2017-05-16  4:08       ` Jeff King
2017-05-16 16:45       ` Eric Rannaud
2017-05-16 10:46     ` Johannes Schindelin
2017-05-16 10:23 ` Johannes Schindelin
2017-05-16 16:18   ` Jeff King
2017-05-16 16:59     ` Eric Rannaud
2017-05-16 17:14       ` Kevin Daudt
2017-05-16 17:29         ` Eric Rannaud
2017-05-16 17:41           ` Jeff King
2017-05-16 17:21       ` Eric Rannaud
2017-05-16 17:37         ` Jeff King

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