[Rd] Tcl socket server (tcltk) does not work any more on R 4.3.2
peter dalgaard
pd@|gd @end|ng |rom gm@||@com
Wed Feb 21 17:49:41 CET 2024
The obvious problem with
while (Tcl_DoOneEvent(TCL_DONT_WAIT) && max_ev) max_ev—;
is that once something does the http server thing, you'll be running Tcl_DoOneEvent max_ev times, _every_ time you hit TclSpinLoop.
I wonder it we could some sort of hybrid between this and Tcl_ServiceAll()? Like, calling Tcl_DoOneEvent once before/after Tcl_ServiceAll().
- Peter
> On 21 Feb 2024, at 17:04 , Tomas Kalibera <tomas.kalibera using gmail.com> wrote:
>
>
> On 2/21/24 08:01, webmail.gandi.net wrote:
>> Thank you, Ivan for this investigation. I inspected the R changes file (https://cran.r-project.org/doc/manuals/r-devel/NEWS.html) and found nothing about this. I should inspect the sources too!
>>
>> It could possibly break other Tcl/Tk related stuff. The doc about Tcl_ServiceAll and Tcl_DoOneEvent is confusing. On one hand, it says when Tcl is used from an external program, Tcl_ServiceAll should be used in its event loop instead of Tcl_DoOneEvent (and the change in the latest R versions goes in that direction). But in the other hand, it is indicated that Tcl_ServiceAll does not always handle all Tcl events and extra Tcl_DoOneEvent should be called in this case. I think we spotted one case where Tcl_ServiceAll is not doing its job correctly. There may be others.
>>
>> Since the {tcltk} package was working fine with "while (Tcl_DoOneEvent(TCL_DONT_WAIT) && max_ev) max_ev—;", unless there is a clear performance enhancement with "while (i-- && Tcl_ServiceAll())", it would perhaps be wise to revert this back.
>
> Yes, for now I've done that in R-devel. The Tcl documentation is really hard to follow, but debugging reveals that Tcl_ServiceAll() doesn't queue new events, as also Ivan reports.
>
> Tomas
>
>>
>> Indeed, when I use this on the server side with R 4.3.2:
>>
>> library(tcltk)
>> cmd <- r"(
>> proc accept {chan addr port} { ;# Make a proc to accept connections
>> puts "$addr:$port says [gets $chan]" ;# Receive a string
>> puts $chan goodbye ;# Send a string
>> close $chan ;# Close the socket (automatically flushes)
>> } ;#
>> socket -server accept 12345 ;# Create a server socket)"
>> .Tcl(cmd)
>> .Tcl("vwait myvar")
>>
>> It works again as expected. And vwait is known to call Tcl_DoOneEvent. Of course, in this case, R is blocked and waits for the `myvar` variable on the Tcl side. Anyway, the problem seems to be really in Tcl_ServiceAll not catching all Tcl events.
>>
>> All the best,
>>
>> Philippe
>>
>> ..............................................<°}))><........
>> ) ) ) ) )
>> ( ( ( ( ( Prof. Philippe Grosjean
>> ) ) ) ) )
>> ( ( ( ( ( Numerical Ecology
>> ) ) ) ) ) Mons University, Belgium
>> ( ( ( ( (
>> ..............................................................
>>
>>> Le 20 févr. 2024 à 17:13, Ivan Krylov via R-devel <r-devel using r-project.org> a écrit :
>>>
>>> В Tue, 20 Feb 2024 12:27:35 +0100
>>> "webmail.gandi.net" <phgrosjean using sciviews.org> пишет:
>>>
>>>> When R process #1 is R 4.2.3, it works as expected (whatever version
>>>> of R #2). When R process #1 is R 4.3.2, nothing is sent or received
>>>> through the socket apparently, but no error is issued and process #2
>>>> seems to be able to connect to the socket.
>>> The difference is related to the change in
>>> src/library/tcltk/src/tcltk_unix.c.
>>>
>>> In R-4.2.1, the function static void TclSpinLoop(void *data) says:
>>>
>>> int max_ev = 100;
>>> /* Tcl_ServiceAll is not enough here, for reasons that escape me */
>>> while (Tcl_DoOneEvent(TCL_DONT_WAIT) && max_ev) max_ev--;
>>>
>>> In R-devel, the function instead says:
>>>
>>> int i = R_TCL_SPIN_MAX;
>>> while (i-- && Tcl_ServiceAll())
>>> ;
>>>
>>> Manually calling Tcl_DoOneEvent(0) from the debugger at this point
>>> makes the Tcl code respond to the connection. Tcl_ServiceAll() seems to
>>> be still not enough. I'll try reading Tcl documentation to investigate
>>> this further.
>>>
>>> --
>>> Best regards,
>>> Ivan
>>>
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>>
>> [[alternative HTML version deleted]]
>>
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Peter Dalgaard, Professor,
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