Spinning in _XReply

[Michal Suchanek]

On 23 February 2011 11:15, Rami Ylimäki <rami.ylimaki at vincit.fi> wrote:
> On 02/22/2011 11:26 PM, xmail at karlt.net wrote:
>>
>> Although wrong, our code has been working well enough for us to get
>> useful information.  If someone is able to point out a reason why
>> this now works less successfully than previously, then that would
>> bump up the priority at our end.
>
> By superficially looking at the Xlib code, the behavior in older Xlib
> version (1.3.3) is different depending on whether Xlib is configured
> --with-xcb or --without-xcb. When Xcb is disabled, error handler is called
> with display unlocked and _XReply seems to be prepared to handle requests
> from error handler. With Xcb, which is the default now with Xlib 1.4, the
> display remains locked during error handling and nested requests aren't
> allowed.
>
> Even the older _XReply contains a comment indicating that doing requests
> from an error handler wasn't considered good behavior even though it
> happened to work previously:
>
>    /* Pull out the serial number now, so that (currently illegal) requests
>     * generated by an error handler don't confuse us.
>     */
>
>> The information we want is already on display->ext_procs->codes
>> but "This structure is private to the library."  I'm not aware of
>> a public API to get this information from Xlib.
>>
>> I guess we could use a separate connection to query the extension
>> codes.  Is it reasonable to assume that all connections to the
>> same display would use the same codes?
>
> X server seems to preserve the extension codes until the server is
> regenerated and therefore all connections should use the same codes.
>

Is that guaranteed by some protocol or does it just happen to work as
the requests in error handler did?

Thanks

Michal