trap ': $((brokenpipe+=1))' PIPE

P=${TMPDIR:-/tmp}
cd $P
T=$(mktemp -d sh-test.XXXXXX)
cd $T

brokenpipe=0
mkfifo fifo1 fifo2
read dummy >fifo2 <fifo1 &
{
	exec 4>fifo2
} 3<fifo2 # Formerly, sh would keep fd 3 and a duplicate of it open.
echo dummy >fifo1
if [ $brokenpipe -ne 0 ]; then
	rc=3
fi
wait
echo dummy >&4 2>/dev/null
if [ $brokenpipe -eq 1 ]; then
	: ${rc:=0}
fi

rm fifo1 fifo2
rmdir ${P}/${T}
exit ${rc:-3}