Bug 142899

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Description of problem:
I have a simple program (I'll try to attach it) which forks a child.
The child sleeps and the parent calls waitpid(childpid, &status,
WNOHANG) in a loop. While child sleeps waitpid returns 0 like it
should.  Then I go and attach to the child with a debugger. When I do
that the parent's behavior change: waitpid starts returnign -1 and
errno is set to 10 (no child processes). Once I restart child in the
debugger waitpid goes backto normal behavior. 
This is bad because there is no way to tell with waitpid whether child
process is being debugger or is gone.
RH ES 3 does not have this problem.

I also tried changing WNOHANG to WNOHANG | WUNTRACED 
and looking at WIFSTOPPED() but that didn't change anything and
WIFSTOPPED is always 0.

Version-Release number of selected component (if applicable):
glibc-2.2.4-32.18, kernel-2.4.9-e.57

How reproducible:
Always

Steps to Reproduce:
1. Run the sample program
2. Attach to the child process with gdb
3. Profit!
    

Actual Results:  waited: pid 0 status: 134514001 errno: 0 0
...
waited: pid -1 status: 134514001 errno: 10 0
...
waited: pid 1736 status: 0 errno: 0 0

Expected Results:  waited: pid 0 status: 134514001 errno: 0 0
...
waited: pid 1736 status: 0 errno: 0 0

Additional info:

#include <stdlib.h>  
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>

main()
{
	pid_t pid, wpid;
	int status;
	
	pid = fork();
	if( pid != 0 )
	{
		printf("parent of child: %d\n", pid);
		while(1)
		{
			errno = 0;
			wpid = waitpid(pid, &status, WNOHANG | WUNTRACED);
			printf("waited: pid: %d status: %d errno: %d %d\n", wpid, status,
errno, WIFSTOPPED(status));
			sleep(1);
		}
	}
	else
	{
		int i;
		for (i = 0; i < 15; i++)
		{
			sleep(1);
		}
		printf("child done\n");
		exit(0);
	}
}