Program chaining on Windows

[Eryk Sun]

On 8/23/20, Chris Angelico <rosuav at gmail.com> wrote:
> On Mon, Aug 24, 2020 at 7:40 AM dn via Python-list
>
>> As a 'general rule', isn't exec() something to be avoided?
>
> Nope, it's a very important tool. Not for every situation, of course,
> but there are plenty of times when it's the right thing to do.

In POSIX, yes, but the faked implementation in Windows is almost
always the wrong choice. Since the exec functions in Windows simply
spawn a new process and exit the current process instead of replacing
the executable image of the current process, they result in broken
semantics for a waiting parent process, both in terms of getting the
correct exit status and waiting for the process to exit. The result of
the latter is an unworkable mess with console applications, since both
the parent and child will compete for console I/O.

For Windows, we need to spawn, wait, and proxy the exit status. If
possible, the spawned child process should also be added to a
kill-on-close job object, like the py.exe launcher does. That way if
the waiting parent crashes or gets terminated, the spawned child will
be terminated as well.