This simple script will reliably crash R 3.1.3

suppressMessages(library(dplyr))
sessionInfo()
df <- data.frame(groups=c(1, 2, 3, 4,4,4), value=1)
df %>%
    group_by(groups) %>%
    do( {
           .[.$value==first(.$value)]
       })

Traceback is,

 *** caught segfault ***
address (nil), cause 'memory not mapped'
Traceback:
 1: .Call("dplyr_rbind_all", PACKAGE = "dplyr", dots)
 2: rbind_all(out[[1]])
 3: label_output_dataframe(labels, out, groups(.data))
 4: do_.grouped_df(.data, .dots = lazyeval::lazy_dots(...))
 5: do_(.data, .dots = lazyeval::lazy_dots(...))
 6: do(., {    .[.$value == first(.$value)]})
 7: function_list[[k]](value)
 8: withVisible(function_list[[k]](value))
 9: freduce(value, `_function_list`)
10: `_fseq`(`_lhs`)
11: eval(expr, envir, enclos)
12: eval(quote(`_fseq`(`_lhs`)), env, env)
13: withVisible(eval(quote(`_fseq`(`_lhs`)), env, env))
14: df %>% group_by(groups) %>% do({    .[.$value == first(.$value)]})

Can be avoided by properly indexing dataframe in do() clause, e.g. just putting a ',' to fetch all columns of the group:

df %>%
    group_by(groups) %>%
    do( {
           .[.$value==first(.$value),]
       })

> sessionInfo()
R version 3.1.3 (2015-03-09)
Platform: x86_64-unknown-linux-gnu (64-bit)
Running under: Ubuntu 14.04.2 LTS
locale:
 [1] LC_CTYPE=en_US.utf8       LC_NUMERIC=C              LC_TIME=en_US.utf8        LC_COLLATE=en_US.utf8     LC_MONETARY=en_US.utf8    LC_MESSAGES=en_US.utf8
 [7] LC_PAPER=en_US.utf8       LC_NAME=C                 LC_ADDRESS=C              LC_TELEPHONE=C            LC_MEASUREMENT=en_US.utf8 LC_IDENTIFICATION=C
attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base
other attached packages:
[1] dplyr_0.4.1
loaded via a namespace (and not attached):
[1] assertthat_0.1.0.99 DBI_0.3.1           magrittr_1.5        parallel_3.1.3      Rcpp_0.11.4