R devel - Feb 2024 - Tcl socket server (tcltk) does not work any more on R 4.3.2

Dear list,

It seems that something changed between R 4.2.3 and R 4.3 (tested with 4.3.2)
that broke the Tcl socket server. Here is a reproducible example:

- R process #1 (Tcl socket server):

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)

- R process #2 (socket client):

con <- socketConnection(host = "localhost", port = 12345, blocking
= FALSE)
writeLines("Hello, world!", con) # Should print something in R #1
stdout
readLines(con) # Should receive "goodbye"
close(con)

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.

I am stuck with this. Thanks in advance for help.

Regards,

Philippe
> .Tcl("puts [info patchlevel]")
8.6.13
<Tcl>  
> sessionInfo()
R version 4.3.2 (2023-10-31)
Platform: aarch64-apple-darwin20 (64-bit)
Running under: macOS Sonoma 14.2.1

Matrix products: default
BLAS:  
/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK:
/Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/lib/libRlapack.dylib;
LAPACK version 3.11.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: Europe/Brussels
tzcode source: internal

attached base packages:
[1] tcltk     stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] compiler_4.3.2 tools_4.3.2    glue_1.7.0

On 20 February 2024 at 12:27, webmail.gandi.net wrote:
| Dear list,
| 
| It seems that something changed between R 4.2.3 and R 4.3 (tested with 4.3.2)
that broke the Tcl socket server. Here is a reproducible example:
| 
| - R process #1 (Tcl socket server):
| 
| 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)
| 
| - R process #2 (socket client):
| 
| con <- socketConnection(host = "localhost", port = 12345,
blocking = FALSE)
| writeLines("Hello, world!", con) # Should print something in R #1
stdout
| readLines(con) # Should receive "goodbye"
| close(con)
| 
| 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.
| 
| I am stuck with this. Thanks in advance for help.
>From a quick check this issue seems to persist in the (current) R-devel
2024-02-20 r85951 too.

Dirk

| Regards,
| 
| Philippe
| 
| > .Tcl("puts [info patchlevel]")
| 8.6.13
| <Tcl>  
| 
| > sessionInfo()
| R version 4.3.2 (2023-10-31)
| Platform: aarch64-apple-darwin20 (64-bit)
| Running under: macOS Sonoma 14.2.1
| 
| Matrix products: default
| BLAS:  
/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
| LAPACK:
/Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/lib/libRlapack.dylib;
LAPACK version 3.11.0
| 
| locale:
| [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
| 
| time zone: Europe/Brussels
| tzcode source: internal
| 
| attached base packages:
| [1] tcltk     stats     graphics  grDevices utils     datasets  methods   base
| 
| loaded via a namespace (and not attached):
| [1] compiler_4.3.2 tools_4.3.2    glue_1.7.0  
| ______________________________________________
| R-devel at r-project.org mailing list
| https://stat.ethz.ch/mailman/listinfo/r-devel

-- 
dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

? Tue, 20 Feb 2024 12:27:35 +0100
"webmail.gandi.net" <phgrosjean at sciviews.org> ?????:
> 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