## Setkey for join
setkey(DT, A)

## Join, with no rows selected.  No problem
DT[ DT[FALSE] ]

## HOWEVER, IF A IS CHARACTER, SEGFAULT WILL RESULT
DT[, A:= as.character(A)]

## Setkey for join
setkey(DT, A)

## THIS WILL CAUSE SEGFAULT
DT[ DT[FALSE] ]

> sessionInfo()
R version 3.0.2 (2013-09-25)
Platform: x86_64-apple-darwin10.8.0 (64-bit)

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] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.8.11 sos_1.3-8         brew_1.0-6       

loaded via a namespace (and not attached):
[1] plyr_1.8       reshape2_1.2.2 stringr_0.6.2 

--------

ByteCompile: TRUE
Repository: R-Forge
Repository/R-Forge/Project: datatable
Repository/R-Forge/Revision: 1160