[Chicken-hackers] Fixing the "process" procedure to be safe against execve() errors

[Lassi Kortela]

I started writing a patch to fix the problems I discovered in this 
thread on chicken-users: 
<https://lists.nongnu.org/archive/html/chicken-users/2019-07/msg00041.html>. 
Is this desired?

If it is: I got stuck on finding the right way to do poll()/select() in 
Chicken. From cursory grepping, Chicken seems to have its own thread 
scheduler which does some calls to poll. I don't understand the 
implications, so I stopped to ask for help instead of going ahead and 
wrapping Unix poll() in the obvious manner.

So the parent process creates a pipe and forks a child process for the 
sole purpose of doing execve(). If the execve() fails the child writes 
the errno value to the pipe. What should the parent do to 
select()/poll() on the pipe and read the errno value?