[bug-diffutils] bug#34519: Test "colors" fails on Debian/ppc64el

[Santiago Vila]

Hello.

I've just uploaded diffutils 3.7 for Debian unstable (hopefully to be
part of Debian 10, since it contains only small fixes).

But there is a problem: The build in the ppc64el autobuilder failed:

https://buildd.debian.org/status/logs.php?pkg=diffutils&ver=1%3A3.7-1&arch=ppc64el

In tests/colors there was a race condition which I tried to fix
by adding a "sleep 1", like this:

mkfifo fifo
printf '%1000000s-a' > a
printf '%1000000s-b' > b
head -c 10 < fifo > /dev/null &
sleep 1
diff --color=always ---presume-output-tty a b > fifo
test $? = 141 || fail=1

It is possible that the "head" command takes (sometimes) more than one second to
complete on ppc64el?

Are there any other places in the test where a race condition could be
happening?

Thanks.