4.3.42 : shopt -s lastpipe & "no record of process" warnings

[Jason Vas Dias]

With a build of bash 4.3 patchlevel 42
on a Linux x86_64 system I am getting
warning messages on stderr when
running a certain script like:
   "wait_for: no record of process 8278" .
Running bash with the script as
input under strace shows that process 8277
does a successful wait4(-1,...) which DOES
return pid 8278 . So why is bash complaining
it has no record of it ?
Is bash getting its book-keeping wrong here?
The script is not using any background
jobs with '&' or using the 'wait' built-in.
It is simply doing something like:
<quote><pre>
shopt -s lastpipe;
set -o pipefail;
function f()
{ some_executable "$@" | {
     while read line; do { ... ; } done;
   }
   return 0;
}
...
f  $args | { while read result; do
...; done ; }
</pre></quote>

So I'd expect the initial bash process to run
a subshell bash to invoke the f() function,
which runs a command child that execve-s
"some_executable', parsing its output and writing
to the subshell bash on a pipe, which writes to the
parent bash on a pipe, which parses it & does whatever.
Without the lastpipe option, this would be the
other way round - the parent would run f, and
its output would be parsed in the subshell
running the f output parsing loop.
All this seems to work OK, but why the warning
message about "no record of process X"?
Or is this message indicating something has
gone seriously wrong ?
Thanks in advance for any replies,
Regards,
Jason