Re: [Qemu-devel] [PATCH v6 4/7] qemu.py: improve message on negative exit code

[Markus Armbruster <armbru@redhat.com>]

Amador Pahim <apahim@redhat.com> writes:

> The current message shows 'self._args', which contains only part of the
> options used in the qemu command line.
>
> This patch makes the qemu full args list an instance variable and then
> uses it in the negative exit code message.
>
> Signed-off-by: Amador Pahim <apahim@redhat.com>
> ---
>  scripts/qemu.py | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/qemu.py b/scripts/qemu.py
> index e3ea534ec4..9434ccc30b 100644
> --- a/scripts/qemu.py
> +++ b/scripts/qemu.py
> @@ -48,6 +48,7 @@ class QEMUMachine(object):
>          self._iolog = None
>          self._socket_scm_helper = socket_scm_helper
>          self._debug = debug
> +        self._qemu_full_args = None
>  
>      # This can be used to add an unused monitor instance.
>      def add_monitor_telnet(self, ip, port):
> @@ -140,9 +141,14 @@ class QEMUMachine(object):
>          qemulog = open(self._qemu_log_path, 'wb')
>          try:
>              self._pre_launch()
> -            args = self._wrapper + [self._binary] + self._base_args() + self._args
> -            self._popen = subprocess.Popen(args, stdin=devnull, stdout=qemulog,
> -                                           stderr=subprocess.STDOUT, shell=False)
> +            self._qemu_full_args = None
> +            self._qemu_full_args = (self._wrapper + [self._binary] +
> +                                    self._base_args() + self._args)

Why set self._qemu_full_args twice?

> +            self._popen = subprocess.Popen(self._qemu_full_args,
> +                                           stdin=devnull,
> +                                           stdout=qemulog,
> +                                           stderr=subprocess.STDOUT,
> +                                           shell=False)
>              self._post_launch()
>          except:
>              if self.is_running():
> @@ -163,8 +169,9 @@ class QEMUMachine(object):
>  
>              exitcode = self._popen.wait()
>              if exitcode < 0:
> -                LOG.error('qemu received signal %i: %s', -exitcode,
> -                          ' '.join(self._args))
> +                LOG.error('qemu received signal %i:%s', -exitcode,
> +                          ' Command: %r.' % ' '.join(self._qemu_full_args)
> +                          if self._qemu_full_args else '')

The last argument is hard to read.

>              self._load_io_log()
>              self._post_shutdown()

The subprocess module appears to keep track of the full command with
methods check_call() and check_output(): its in exception
CalledProcessError right when you need it.  Sadly, it doesn't appear to
be tracked with method Popen().