printing send() with signals == character(0) causes the R session to crash

[tomjemmett]

steps to reproduce:

library(simmer)
send(trajectory(), character(0))

this causes the entire R session to crash.

however, assigning send() to a variable works fine, e.g.

t <- send(trajectory(), character(0))

but then running print(t) will cause the session to crash. running send with a value works fine

send(trajectory(), "abc")

and running this works fine

simmer() |>
  add_generator("x", send(trajectory(), character(0)), at(0)) |>
  run()

[tomjemmett]

session info if useful:

- Session info -------------------------------------------------------------------------------------------
 setting  value                       
 version  R version 4.1.0 (2021-05-18)
 os       Windows 10 x64              
 system   x86_64, mingw32             
 ui       RStudio                     
 language (EN)                        
 collate  English_United Kingdom.1252 
 ctype    English_United Kingdom.1252 
 tz       Europe/London               
 date     2021-07-01                  

- Packages -----------------------------------------------------------------------------------------------
 package     * version date       lib source        
 cachem        1.0.5   2021-05-15 [1] CRAN (R 4.1.0)
 callr         3.7.0   2021-04-20 [1] CRAN (R 4.1.0)
 cli           2.5.0   2021-04-26 [1] CRAN (R 4.1.0)
 codetools     0.2-18  2020-11-04 [1] CRAN (R 4.1.0)
 crayon        1.4.1   2021-02-08 [1] CRAN (R 4.1.0)
 desc          1.3.0   2021-03-05 [1] CRAN (R 4.1.0)
 devtools      2.4.1   2021-05-05 [1] CRAN (R 4.1.0)
 ellipsis      0.3.2   2021-04-29 [1] CRAN (R 4.1.0)
 fastmap       1.1.0   2021-01-25 [1] CRAN (R 4.1.0)
 fs            1.5.0   2020-07-31 [1] CRAN (R 4.1.0)
 glue          1.4.2   2020-08-27 [1] CRAN (R 4.1.0)
 lifecycle     1.0.0   2021-02-15 [1] CRAN (R 4.1.0)
 magrittr      2.0.1   2020-11-17 [1] CRAN (R 4.1.0)
 memoise       2.0.0   2021-01-26 [1] CRAN (R 4.1.0)
 pkgbuild      1.2.0   2020-12-15 [1] CRAN (R 4.1.0)
 pkgload       1.2.1   2021-04-06 [1] CRAN (R 4.1.0)
 prettyunits   1.1.1   2020-01-24 [1] CRAN (R 4.1.0)
 processx      3.5.2   2021-04-30 [1] CRAN (R 4.1.0)
 ps            1.6.0   2021-02-28 [1] CRAN (R 4.1.0)
 purrr         0.3.4   2020-04-17 [1] CRAN (R 4.1.0)
 R6            2.5.0   2020-10-28 [1] CRAN (R 4.1.0)
 Rcpp          1.0.6   2021-01-15 [1] CRAN (R 4.1.0)
 remotes       2.4.0   2021-06-02 [1] CRAN (R 4.1.0)
 rlang         0.4.11  2021-04-30 [1] CRAN (R 4.1.0)
 rprojroot     2.0.2   2020-11-15 [1] CRAN (R 4.1.0)
 sessioninfo   1.1.1   2018-11-05 [1] CRAN (R 4.1.0)
 simmer      * 4.4.2   2020-06-06 [1] CRAN (R 4.1.0)
 testthat      3.0.3   2021-06-16 [1] CRAN (R 4.1.0)
 usethis       2.0.1   2021-02-10 [1] CRAN (R 4.1.0)
 withr         2.4.2   2021-04-18 [1] CRAN (R 4.1.0)

[1] C:/Program Files/R/R-4.1.0/library

[Enchufa2]

Confirmed, thanks. And this probably happens with other activities and arguments too.