Re: [Qemu-devel] [PATCH v5 3/6] qemu.py: cleanup message on negative exit code

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Jul 25, 2017 at 07:10:11PM +0200, Amador Pahim wrote:
> The message contains the self._args, which has only part of the
> options used in the qemu command line and is not representative
> enough to figure out what happened to the process.
> 
> This patch drops the self._args part of the message.
> 
> Signed-off-by: Amador Pahim <apahim@redhat.com>

I actually think it is a very useful debugging message as is,
because the command-line arguments are often all we need to
reproduce a QEMU crash.

That said, sys.stderr.write doesn't belong to the QEMUMachine
code, as callers should decide if/when/how/where to print
information about a QEMU crash.

I think a QEMUCrashed exception class would be the best way to
report that to callers.  Including the full QEMU command-line on
the exception __str__ method would make it helpful when debugging
crashes: existing code that doesn't catch launch() exceptions
will crash with a more helpful stack trace, and code that already
catches exceptions is probably going to print exception info
somewhere.


> ---
>  scripts/qemu.py | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/qemu.py b/scripts/qemu.py
> index f37e2fe58e..56142ed59b 100644
> --- a/scripts/qemu.py
> +++ b/scripts/qemu.py
> @@ -154,7 +154,8 @@ class QEMUMachine(object):
>  
>              exitcode = self._popen.wait()
>              if exitcode < 0:
> -                sys.stderr.write('qemu received signal %i: %s\n' % (-exitcode, ' '.join(self.args)))
> +                sys.stderr.write('qemu received signal %i\n' % -exitcode)
> +
>              self._load_io_log()
>              self._post_shutdown()
>  
> -- 
> 2.13.3
> 

-- 
Eduardo