bash bug: wait_for: No record of process (had been fixed in bash 5.1+)

bash_bug_wait_for.sh

#!/usr/bin/env bash

#
# Reproducer for bash bug that had been fixed in bash 5.1+ [1], report [2]
#
#   [1]: https://git.savannah.gnu.org/cgit/bash.git/commit/?h=bash-5.1&id=8868edaf2250e09c4e9a1c75ffe3274f28f38581
#   [2]: https://lists.gnu.org/archive/html/bug-bash/2019-05/msg00110.html
#

function thread_worker()
{
    set -e

    # echo "thread_worker_pid=$BASHPID (started)"

    trap "STOP_THE_LOOP=1; sleep 0.5" INT
    STOP_THE_LOOP=0
    while [[ $STOP_THE_LOOP != 1 ]]; do
        sleep 0.1 | grep foo || :
    done

    # echo "thread_worker_pid=$BASHPID (finished)"
}

function main()
{
    echo "main_pid=$BASHPID"

    local pids=()
    for i in $(seq 0 100); do
        thread_worker &
        pids+=( $! )
    done

    sleep 0.1

    echo "Sending INT"
    wait &
    sleep 0.1
    kill -INT "${pids[@]}"
    sleep 0.1
    wait
}
main "$@"

$ timeout -v 1m bash -c 'while docker run --rm -v $PWD:/wrk -w /wrk bash:5.1 ./test5.sh; do :; done |& fgrep -m1 wait_for:'
timeout: sending signal TERM to command ‘bash’
$ timeout -v 1m bash -c 'while docker run --rm -v $PWD:/wrk -w /wrk bash:5.0.17 ./test5.sh; do :; done |& fgrep -m1 wait_for:'
/wrk/test5.sh: line 1: wait_for: No record of process 616