CHLD traps run at the same time

[Øyvind 'bolt' Hvidsten]

I'm responsible for a couple of scripts at work, which have used a trap 
on CHLD to do some naive parallelisation, starting a new child process 
when an existing one ends.

However, when run under bash 4.3.30, all CHLD traps run at the same 
time, so my script runs in chunks, rather than keeping a given amount of 
processes running at all times. I've been told I can rewrite it using 
wait -n instead, but I'm wondering if this is classified as a bug, or if 
it's intended to be that way going forwards.

Here's a quick example of what happens (from shbot in #bash on freenode):

43# bash -c "echo \$BASH_VERSION; set -m; trap 'date' CHLD; sleep 1 & 
sleep 3"
4.3.30(1)-release
[1]+  Done                    sleep 1
Wed Jan 14 10:58:33 UTC 2015
Wed Jan 14 10:58:33 UTC 2015

42# bash -c "echo \$BASH_VERSION; set -m; trap 'date' CHLD; sleep 1 & 
sleep 3"
4.2.53(1)-release
Wed Jan 14 10:58:36 UTC 2015
Wed Jan 14 10:58:38 UTC 2015
[1]+  Done                    sleep 1