loadable sleep exits immediately

[p . debruijn]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: /opt/project/buildroot/output/host/bin/x86_64-buildroot-linux-gnu-gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-buildroot-linux-gnu' 
-DCONF_VENDOR='buildroot' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' 
-DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_LARGEFILE_SOURCE 
-D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE 
-D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -O2  -D_FORTIFY_SOURCE=1 
-Wno-parentheses -Wno-format-security
uname output: Linux netbootbox 4.14.153 #6 SMP Tue Nov 12 14:20:37 CET 2019 
x86_64 GNU/Linux
Machine Type: x86_64-buildroot-linux-gnu

Bash Version: 4.4
Patch Level: 23
Release Status: release

Description:
        The loadable sleep function seems to exit almost immediately
        in some specific cases.

Repeat-By:
        The following minimal reproducable example illustrates the issue:

        #!/bin/bash
        enable -f /lib/bash/sleep sleep
        aaa ()
        {
          type sleep
          while true; do
            echo -n "A"
            dmesg >/dev/null &
            sleep $1
          done
        }
        while true; do
          aaa 5 &
          sleep 60
        done

Workaround:
        Use /bin/sleep

        However this is unwatend for long running scripts, where it pollutes
        the process list.