[R-SIG-Mac] tcltk causes help() to hang in R 4.2.0 on macOS

[Simon Urbanek]

Actually, I take back the reference to the commit - the deadlock is true, and removing the line is a work-around, but r78421 was not necessarily the regression. The issue seems to be caused by a combination of Tcl/Tk and KaTeX (the latter causes the browser to issue multiple parallel http-requests and the former causes the deadlock in its event loop) which has not been there in earlier R versions.

Cheers,
Simon


> On 30/05/2022, at 10:09 AM, Simon Urbanek <simon.urbanek using r-project.org> wrote:
> 
> John,
> 
> thanks, this is a regression caused by r78421 (deadlock when TclTk's event loop is called in http processing). Removing L875 in src/modules/internet/Rhttpd.c restores the previous behavior, but the underlying problem is more complex and will require more investigation.
> 
> Cheers,
> Simon
> 
> 
>> On 29/05/2022, at 5:36 AM, John Fox <jfox using mcmaster.ca> wrote:
>> 
>> Dear R-sig-mac list members,
>> 
>> I've discovered that loading the tcltk package apparently causes R 4.2.0 (including the current patched version) to hang on an M1 Mac.
>> 
>> Try, e.g.,
>> 
>> library("tcltk")
>> help("lm")
>> 
>> My session info:
>> 
>> ------- snip -------
>> 
>>> sessionInfo()
>> R version 4.2.0 Patched (2022-05-28 r82413)
>> Platform: aarch64-apple-darwin20 (64-bit)
>> Running under: macOS Monterey 12.3.1
>> 
>> Matrix products: default
>> BLAS: /Library/Frameworks/R.framework/Versions/4.2-arm64/Resources/lib/libRblas.0.dylib
>> LAPACK: /Library/Frameworks/R.framework/Versions/4.2-arm64/Resources/lib/libRlapack.dylib
>> 
>> locale:
>> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
>> 
>> attached base packages:
>> [1] tcltk     stats     graphics  grDevices utils     datasets  methods
>> [8] base
>> 
>> loaded via a namespace (and not attached):
>> [1] compiler_4.2.0
>> 
>> ------- snip -------
>> 
>> Some additional details: The problem occurs both in the R macOS console and, if options(help_type="html"), when R is run in a terminal window on macOS, but not when options(help_type="text"). The former is the default in the Mac R console, the latter when R is run in a terminal.
>> 
>> The problem is apparently new in R 4.2.0 -- it doesn't, e.g., occur in R 4.1.3. My apologies for not turning it up earlier.
>> 
>> I discovered the problem when accessing help in the Rcmdr GUI, which uses tcltk, caused R to hang.
>> 
>> Has anyone else encountered this problem?
>> 
>> Best,
>> John
>> -- 
>> John Fox, Professor Emeritus
>> McMaster University
>> Hamilton, Ontario, Canada
>> web: https://socialsciences.mcmaster.ca/jfox/
>> 
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> 
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