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Date: Thu, 15 Oct 2009 10:33:43 -0400
From: Charles Wilson <cygwin AT cwilson DOT fastmail DOT fm>
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To: cygwin AT cygwin DOT com
Subject: fork failure?
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I'm trying to track down a rather weird problem. I don't have an STC
because none of my attepted STCs exhibit the problem.  Schematically, I
have:

=============================================
pid_t pid = fork();

if (pid < 0) {
  printf("fork failed\n");
  exit (1);
}

if (pid > 0) {
  /* parent */
  printf("parent: child pid=%d\n", pid);
  sleep(30);
  exit(0);
}

/* child */
printf("child lives!");
sleep(30);
exit(0);
=============================================

although the actual app is much more complicated, AND an STC based on
the above actually works as expected. But, in the actual app, what
happens is:

1) fork appears to succeed, because I see:
parent: child pid=xxx

2) but fork fails, because I never see:
child lives!
Worse, I never see the pid xxx show up in 'ps' output, even though I
have plenty of time (30 seconds) to spot it (and STCs based on the above
simplification do work as expected; I see 'child lives!' and the process
shows up in 'ps').

I even tried (in the actual app) other methods of indication than
printing to some FILE*, since maybe stdout got scrogged by fork, such as:
a) writing to an inherited fd other than 0,1,2
b) writing to a brand new fd or FILE* opened by the child
c) simply touching a "sentinel" file to change its atime
Nothing. For all I can tell, the fork() fails to *actually* produce a
child process -- even though the *parent* seems to think one has been
created, and has a pid for the so-called child. Which doesn't actually
exist.

Can anybody think of a reason that might cause this behavior? I'm using
stock cygwin-1.7.0-62...

--
Chuck

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