Re: [Qemu-devel] Re: monitor: check for readline in monitor_event()

[Jan Kiszka <jan.kiszka@web.de>]

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Luiz Capitulino wrote:
> On Tue, 16 Jun 2009 00:42:26 +0200
> Jan Kiszka <jan.kiszka@web.de> wrote:
> 
>> Luiz Capitulino wrote:
>>> The call of readline_show_prompt() in CHR_EVENT_RESET's body will
>>> trig a segfault if readline is not being used, because 'mon->rs'
>>> will be NULL.
>>>
>>> This fixes the problem by adding the proper check.
>>>
>>> I've trigged this while playing with an off-tree code that disables
>>> readline support, I'm not sure whether in-tree code can trig this.
>>>
>>> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
>>> ---
>>>  monitor.c |    2 +-
>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/monitor.c b/monitor.c
>>> index 6b45f6c..787101d 100644
>>> --- a/monitor.c
>>> +++ b/monitor.c
>>> @@ -3002,7 +3002,7 @@ static void monitor_event(void *opaque, int
>>> event) case CHR_EVENT_RESET:
>>>          monitor_printf(mon, "QEMU %s monitor - type 'help' for
>>> more " "information\n", QEMU_VERSION);
>>> -        if (mon->chr->focus == 0)
>>> +        if (mon->rs && mon->chr->focus == 0)
>>>              readline_show_prompt(mon->rs);
>>>          break;
>>>      }
>> In-tree code is not affected as no monitor user will call
>> qemu_chr_reset for the associated char device if there is no readline
>> active as well. Yeah, secret de-facto rule.
> 
>  Ok.
> 
>> The patch is not incorrect, but I would like to understand the
>> out-of-tree use case behind it. So you do want the info line printed,
>> but provide your own readline processor? What kind of terminal is
>> this?
> 
>  I'm working on a machine-friendly monitor for QEMU, which disables
> readline.

Again, I bet that your monitor will not be interested in the prompt
header. So I think we should rather exclude the whole CHR_EVENT_RESET
path for the !mon->rs case.

> 
>  I didn't want to get into the details now, it will be better to
> discuss the prototype I'm writing, should be finished soon.

Looking forward!

Jan


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