[PATCH] Make sure GDB uses a valid shell when starting the inferior and to perform the "shell" command

[Eli Zaretskii]

> From: Sergio Durigan Junior <sergiodj@redhat.com>
> Cc: simon.marchi@ericsson.com, gdb-patches@sourceware.org
> Date: Sat, 25 Jul 2015 13:03:12 -0400
> 
> The new section says:
> 
>   @node Valid Shell
>   @subsection Valid Shell
> 
>   @value{GDBN} considers a @emph{valid shell} a file that:
> 
>   @enumerate
>   @item
>   Exists and can be executed by the user.
> 
>   @item
>   Is not the @file{/sbin/nologin} (or @file{/usr/sbin/nologin}) program.
> 
>   @item
>   Is not the @file{/bin/false} program.
>   @end enumerate
> 
>   If any of those conditions are not met, the specified shell is not
>   used by @value{GDBN}.
> 
> I do not see any difference from what I said above, but if you think
> this text can be improved, or that this text is not needed at all, then
> by all means feel free to ask this.

The use of "valid" seems to imply much broader goals.  Your
description seems to say that "pseudo-shells used to disable logins"
is a better (though longer) terminology.

Also, I suggest to say "such as the following", so as not to imply
that this is necessarily an exhaustive list.

Finally, is it really OK to lump here the "cannot be executed by the
user" case?  Maybe we should error out in that case.