[PATCH] ephyr: Avoid a segfault with 'DISPLAY= Xephy -glamor'

[Daniel Martin]

On 9 February 2015 at 15:09, Jon TURNEY <jon.turney at dronecode.org.uk> wrote:
> On 09/02/2015 14:03, Daniel Martin wrote:
>>
>> On 9 February 2015 at 14:45, Jon TURNEY <jon.turney at dronecode.org.uk>
>> wrote:
>>>
>>> ephyr_glamor_connect() returns NULL if we failed, but applying
>>> xcb_connection_has_error() to NULL is not permitted.
>>>
>>> Signed-off-by: Jon TURNEY <jon.turney at dronecode.org.uk>
>>> ---
>>>   hw/kdrive/ephyr/hostx.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/hw/kdrive/ephyr/hostx.c b/hw/kdrive/ephyr/hostx.c
>>> index f64861b..15edce8 100644
>>> --- a/hw/kdrive/ephyr/hostx.c
>>> +++ b/hw/kdrive/ephyr/hostx.c
>>> @@ -443,7 +443,7 @@ hostx_init(void)
>>>       else
>>>   #endif
>>>           HostX.conn = xcb_connect(NULL, &HostX.screen);
>>> -    if (xcb_connection_has_error(HostX.conn)) {
>>> +    if (!HostX.conn || xcb_connection_has_error(HostX.conn)) {
>>
>>
>> No need to change the check, as xcb_connect() ...
>>      "Always returns a non-NULL pointer to a xcb_connection_t, even on
>> failure."
>>      http://cgit.freedesktop.org/xcb/libxcb/tree/src/xcb.h#n549
>
>
> I'm afraid you need to look at a little more context than is in the diff.
>
> If glamor is enabled, HostX.conn contains the result of
> ephyr_glamor_connect(), not xcb_connect(), which can be NULL.
>

Ah, I see. Another way to fix it would have been to return such an
error from ephyr_glamor_connect() like xcb_connect() would do. But,
that be more complicated then this simple check ...

Reviewed-by: Daniel Martin <consume.noise at gmail.com>