regression in meson build, AC_PATH_PROG lost

[Martin Kletzander]

On Thu, Nov 19, 2020 at 10:31:00PM +0100, Olaf Hering wrote:
>Am Thu, 19 Nov 2020 22:15:27 +0100
>schrieb Martin Kletzander <mkletzan at redhat.com>:
>
>> Libvirt needs to be able to handle that missing binary at runtime anyway
>
>It also needs to handle an existing binary. Just how is it supposed to handle it?
>

Um... run it?

>Right now with meson it is either a full path, or just the name in case it was missing at build time (I have not checked if the launcher actually consults $PATH).
>

Right now, IMHO, all meson checks for binaries that are not needed at build time
should be removed.  During runtime we can just use the name of the binary.  I
don't know whether it used to be the case that it was thought that there might
be security issues with supplying different binary in a directory in $PATH, but
frankly, if you have (different-)user-writable directory in $PATH or non-root
access to modifying system-wide $PATH then you have bigger problems to deal
with.  Even though I do not have anything to back this claim I think that
might've been the original reason.

>Anyway, what would be the desired approach to tell libvirt the runtime path?
>

Find it at runtime with virFindFileInPath() just like we already do with a few
binaries (and did for some since 2009 or so) or even without it as virCommand()
already searches $PATH since:

commit e0d014f2379ddde175c0c3126273911221c3e645
Author: Daniel P. Berrangé <berrange at redhat.com>
Date:   Tue Mar 15 16:58:28 2011 +0000

     Ensure binary is resolved wrt $PATH in virExec

>I was thinking about something like:
>  option('runtime_path_exe', type: 'string', value: 'exe', description: 'runtime path of exe')
>  runtime_path_exe = get_option('runtime_path_exe')
>  if not get_option('runtime_path_exe').enabled()
>    runtime_path_exe = find_program(runtime_path_exe, required: true).path()
>  conf.set_quoted('EXE', runtime_path_exe)
>
>Olaf

Just for the sake of completeness here are some examples on how to do it:

commit 274f09cbc5ed8be00127380327d9525b852a2d1d
Author: Stefan Berger <stefanb at us.ibm.com>
Date:   Wed Apr 14 06:29:55 2010 -0400

     nwfilter: use virFindFileInPath for needed CLI tools

commit 2e045a4f9bf2757199c0997b9842d8dd8510459f
Author: Daniel P. Berrangé <berrange at redhat.com>
Date:   Thu Jan 19 10:27:11 2017 +0000

     storage: avoid use of undefined GLUSTER_CLI variable

Martin

P.S.: It is not *strictly* necessary that the commit hash starts with '2' ;)
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