Bogus exit code 127 from a child process

[Dimitry Andric]

On 17 Mar 2024, at 13:50, Dimitry Andric <dimitry@unified-streaming.com> wrote:
> 
> On 17 Mar 2024, at 13:35, Takashi Yano via Cygwin <cygwin@cygwin.com> wrote:
> ...
>> 
>> I also test your test case:
>> while bash -c 'true & true & wait -n || { echo 1: $?; exit 1; } && wait -n || { echo 2: $?; exit 1; }'; do echo $((i++)); done
>> in Linux (Debian 12.5), and the issue reproduced!
> 
> Yeah, same here with bash 5.1.16(1)-release on Ubuntu 22.04. It errors out with 127 after ~50-200 loops.

Having built bash master (bash-5.2-27-gf3b6bd19) here, it consistently gives 127 in this area:

https://git.savannah.gnu.org/cgit/bash.git/tree/builtins/wait.def#n227

   211  #if defined (JOB_CONTROL)
   212    if (nflag)
   213      {
   214        if (list)
   215          {
   216            opt = set_waitlist (list);
   217            if (opt == 0)
   218              WAIT_RETURN (127);
   219            wflags |= JWAIT_WAITING;
   220          }
   221
   222        status = wait_for_any_job (wflags, &pstat);
   223        if (vname && status >= 0)
   224          builtin_bind_var_to_int (vname, pstat.pid, bindflags);
   225
   226        if (status < 0)
=> 227          status = 127;
   228        if (list)
   229          unset_waitlist ();
   230        WAIT_RETURN (status);
   231      }
   232  #endif

So for some reason, wait_for_any_job() returns a negative value in this particular situation.

-Dimitry