dplyr::mutate with lubridate::ymd_hms seems to crash R at random

gistfile1.txt

# Posted on StackOverflow: http://stackoverflow.com/questions/31010713/combining-dplyrmutate-with-lubridateymd-hms-in-r-randomly-causes-segfault

#!/usr/bin/env R
# -*- encoding:utf-8 -*-

require(lubridate)
require(dplyr)

set.seed(42)
make_some_random_datetimes = function(n) ymd("2015-01-01") + seconds(runif(n, min=0, max=60*60*24*365))

d = data.frame(
  col1 = make_some_random_datetimes(5000),
  col2 = make_some_random_datetimes(5000)
)

do_it = function() {
  d %>% mutate(
    col1 = ymd_hms(col1),
    col2 = ymd_hms(col2)  # for some reason, it only crashes when evaluating 2+ cols, if we removed this line it'd be fine
  )
  return(TRUE)
}

do_it()  # doesn't crash every time...it fails every nth time where n is randomly distributed with mean of roughly 7.7

do_it_lots_of_times = function(n) for (i in 1:n) do_it()

do_it_lots_of_times(50)  # almost guaranteed to fail on my machine

# Running the above line in RStudio, I just get message "R Session Aborted. R encountered a fatal error. The session was terminated."
# Running the above line in Terminal, I get following
#    *** caught segfault ***
#    address 0x0, cause 'unknown'

# Output of sessionInfo()

# R version 3.2.1 (2015-06-18)
# Platform: x86_64-apple-darwin14.3.0 (64-bit)
# Running under: OS X 10.10.3 (Yosemite)
#
# locale:
# [1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8
#
# attached base packages:
# [1] stats     graphics  grDevices utils     datasets  methods   base     
#
# other attached packages:
# [1] dplyr_0.4.2     lubridate_1.3.3
#
# loaded via a namespace (and not attached):
# [1] lazyeval_0.1.10 R6_2.0.1        assertthat_0.1  magrittr_1.5    plyr_1.8.3      parallel_3.2.1 
# [7] DBI_0.3.1       tools_3.2.1     memoise_0.2.1   Rcpp_0.11.6     stringi_0.5-2   digest_0.6.8   
# [13] stringr_1.0.0  

Try this version out in the interim

require(lubridate)
require(dplyr)
require(data.table)
set.seed(42)
make_some_random_datetimes = function(n) ymd("2015-01-01") + seconds(runif(n, min=0, max=60*60*24*365))

d = data.table(
  col1 = make_some_random_datetimes(5000),
  col2 = make_some_random_datetimes(5000)
)


do_it = function() {
  d %>% .[,`:=`(
    col1 = ymd_hms(col1),
    col2 = ymd_hms(col2)  # for some reason, it only crashes when evaluating 2+ cols, if we removed this line it'd be fine
  )]
  return(TRUE)
}

do_it()  # doesn't crash every time...it fails every nth time where n is randomly distributed with mean of roughly 7.7

do_it_lots_of_times = function(n) for (i in 1:n) do_it()

do_it_lots_of_times(50)