make returning spurious 4522468 errors

We are in the process of migrating from our current Microsoft nmake 
based build system to a platform independent build system based on GNU 
make.  We are encountering a problem in which GNU make sometimes reports 
an error of 4522468 for some jobs only on Windows.  We aren't able to 
reproduce the error on demand - it currently happens somewhere between 1 
and 15 times for every 10000 or so jobs.  I think we've only seen this 
when invoking make with the '-j' option.  Higher occurrences of this 
seem to correspond to higher values for the '-j' option. (ie, '-j 2' 
produces fewer occurrences than '-j 8').  This suggests a race condition 
somewhere in GNU make.  We have not identified any correlation between 
this occurring and the specific job that was run.  We have clear 
examples of make reporting this error even for jobs that completed 
successfully (ie, where we are confident that the job returned an exit 
value of 0).  In some cases, this error has been emitted for a recursive 
make invocation (in which the sub-make returned 0 or 2).

We were originally using the gmake.exe 3.81 binary distributed with 
GNUWin32 (http://gnuwin32.sourceforge.net), but have now reproduced this 
with a binary we built ourselves (also 3.81 using the MS VS 2008 
compiler).  Anyone else seen this?

Based on a brief glance at the code, I'm guessing that the value 
returned by one of the calls to 'GetExitCodeProcess' in 
'w32/subproc/sub_proc.c' is somehow getting lost or corrupted.  There 
are two calls to 'GetExitCodeProcess', both of which look very similar 
to this:

        DWORD ierr;
        GetExitCodeResult = GetExitCodeProcess(childhand, &ierr);
        if (ierr == CONTROL_C_EXIT) {
                pproc->signal = SIGINT;
        } else {
                pproc->exit_code = ierr;
        }
        if (GetExitCodeResult == FALSE) {
                pproc->last_err = GetLastError();
                pproc->lerrno = E_SCALL;
        }

Two things stand out to me here:

1: 'pproc->exit_code' is assigned the value of 'ierr' regardless of 
whether the call to 'GetExitCodeProcess' is successful or not.  If 
'GetExitCodeProcess' fails, it may not assign to 'ierr' at all - which 
could result in 'pproc->exit_code' getting assigned an uninitialized 
value (since 'ierr' is not assigned a value)

2: There is no check for 'ierr' being assigned 'STILL_ACTIVE'.  It may 
be that other parts of the code ensure that 'GetExitCodeProcess' is 
never called for an uncompleted process, I haven't looked for that.  
Regardless, this is unlikely to be related to the problem that we are 
seeing.

Tom.