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

[Eli Zaretskii <eliz@gnu.org>]

> From: Sergio Durigan Junior <sergiodj@redhat.com>
> Cc: Sergio Durigan Junior <sergiodj@redhat.com>
> Date: Fri, 24 Jul 2015 14:19:53 -0400
> 
> It is known that GDB needs a valid shell to start the inferior and to
> offer the "shell" command to the user.  This has recently been the
> cause of a problem on the MIPS buildslave, because $SHELL was set to
> /sbin/nologin and several tests were failing.  The thread is here:
> 
>   <https://sourceware.org/ml/gdb-patches/2015-07/msg00535.html>
> 
> However, I think we can do better than that.  If 'startup-with-shell'
> is on, which is the default, we blindly trust that the user will
> provide a valid shell for us, and this may not be true all the time.
> So I am proposing a patch to increment the tests made by GDB before
> running the inferior to decide whether it will use $SHELL or not.
> Particularly, I created a new function, called "valid_shell", which
> defines the concept of a valid shell for GDB:
> 
>   - A file that exists and is executable by the user
> 
>   - A file that is not /sbin/nologin
> 
> For now, I think this is enough to cover most cases.  The default
> action when an invalid shell is found is to use /bin/sh instead (we
> already do that when $SHELL is not defined, for example), and also
> issue a warning to the user.  This applies for when we are starting
> the inferior and when we are executing the "shell" command.
> 
> To make things more robust, I made the code also check /bin/sh and
> make sure it is also valid.  If it is not, and if we are starting the
> inferior, then GDB will use fork+exec instead.  If we are executing
> the "shell" command and we cannot find a valid shell, GDB will error
> out.
> 
> I updated the documentation to reflect the new behavior, and created a
> testcase to exercise the code.  This patch has been regression-tested
> on Fedora 22 x86_64.
> 
> OK to apply?

The documentation part is OK, but please use @pxref instead of "see
@ref" for cross-references in parentheses.

Thanks.