comm: "- -" deadlocks #14219

coreutils 0.10.0 (multi-call binary), latest commit

uutils comm hangs:

printf 'test' | ./comm - -

gnu comm behaves differently:

printf 'test' | gnucomm - -
test
gnucomm: -

gnu comm's behavior seems non-deterministic, with larger inputs it leaves stray leftovers and cuts lines based on glibc stdio buffer sizes.

Possible solutions would be to
a) replicate gnu comm's behavior or
b) reject "- -" as arguments