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vfork alternatives?

We have an application that mmaps a *huge* MAP_PRIVATE|MAP_ANON virtual
address scratch space.  It also needs to occasionally fork/exec a sub
process.  Unfortunately, the time and virtual memory required for Cygwin
to copy this region to the forked child just so it can throw it away and
do an exec is prohibitive if it's even possible.

I know that a real vfork has been tried without success so far, but I was
wondering if anyone had any suggestions to work around this specific type
of issue?  Maybe some no copy flag to mmap?

As an aside, one of our developers made a simple system() replacement via
CreateProcess that was working in 1.5.18.  In 1.5.19, Cygwin environment
variables are no longer passed along via his mechanism.  I know that
subverting Cygwin in this way is not supported, and I'd like a more
general solution, so I haven't yet tried to figure out what broke or if
there is still a way around it.

Any rough suggestions for a way for us to help Cygwin cope with this kind
of scenario would be greatly appreciated.  Thanks.

Brian Ford
Lead Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained pilot...

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