XInitThreads in library constructor breaks Motif!

[Po Lu]

On October 31, 2022 7:08:50 AM GMT+08:00, Alan Coopersmith <alan.coopersmith at oracle.com> wrote:
>On 10/29/22 19:00, Po Lu wrote:
>> Motif assumes that you can call functions that lock the display inside
>> XCheckIfEvent as it never calls XInitThreads itself.  It also never uses
>> threads.
>
>It was never up to Motif to decide whether or not to call XInitThreads()
>- that decision was up to the applications, and if Motif assumed no
>application would ever do that, it was buggy and incompatible with such
>applications.

Okay, so what about the countless Motif *applications* that don't use threads?  Motif is not a thread-safe library, and is documented as such, so Motif applications (mine included) deliberately do not call XInitThreads.

>https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/150 is
>a proposed solution to the problem, but has not generated any interest
>in testing it or moving it forward, suggesting either everyone is
>building with the --disable-thread-safety-constructor option or is
>using correctly written software that does not make such assumptions.

Or most people are on Xlib 1.7.x.  Anyway, the documentation for X*IfEvent says it is okay to call functions that take the display lock inside the predicate given that it does not change the event queue.  I have written such software, and clearly the Open Group has too, along with XFCE, etc.

Besides, how to move it forward? If it works, wouldn't the obvious solution be to install the change? If all that is needed is for someone to try it out, I'd be happy to do it, but I'm pretty sure the better solution is just to remove the call to XInitThreads in the first place.

So please don't make arbitrary changes to documented behavior!! There are people who pay for Motif, and such things did not happen when both Motif and Xlib were being developed under the auspices of the Open Group.

Thanks.