Why does Cygwin not use MiCloneProcessAddressSpace() for fork()

Mon Sep 22 11:28:23 GMT 2025

Mark Liam Brown wrote:
> This is exposed to the userspace as NtCreateProcessEx() as documented in
> https://github.com/huntandhackett/process-cloning

From the linked page:
> Unfortunately, it doesn't matter which method we prefer because the results
> will be identically disappointing: STATUS_PROCESS_IS_TERMINATING, or, in other
> words, "An attempt was made to access an exiting process." The system
> considers the cloned threadless process as waiting for deletion and, thus,
> refuses to create threads in it – something we inevitably need to execute
> code. Sorry, but NtCreateProcessEx-based cloning is incompatible with code
> execution.
>> > Note that it wasn't always the case. The kernel allowed creating threads in
> > such processes until Windows 8.1.

Best regards
Oliver
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