How to intepret <defunct> c++ process ubuntu

Question

I'm running some C++ code (8 independent processes running on Ubuntu with 8 cores).

I'm launching the C processes using python:

def runC():
    numThreads = multiprocessing.cpu_count()
    threads = []
    for i in range(numThreads):
        args = ("./cprogram", arg1,arg2,arg3)
        popen = subprocess.Popen(args, stdout=subprocess.PIPE,stderr=subprocess.PIPE)
        threads.append(popen)

    for t in threads:
       t.wait()
       output = t.stdout.read()
       err = t.stderr.read()
       if len(output) > 0:
          print "output: " + output
       if len(err) > 0:
          print "err: " + err

I keep getting "defunct" processes. What does that mean? Why did this happen to me?

Answer 1

Turns out it's the t.wait() that is causing the zombie process. Depending on the order that the jobs finish, there will be some in a zombie state until the t.wait() gets around to them. It's not really a problem, which is what I wanted to be sure of.