[MLton-user] FFI and pointer relocation

[Dave Herman]

If I pass a ref cell through the FFI to some C code which squirrels away 
the pointer and updates it much later, will that always be safe? Or will 
the GC potentially move the location of the ref cell?

I'm using this to pass a bool ref through the FFI as a sort of "mailbox" 
to be notified whenever a particular event has occurred. Then the SML 
code polls the mailbox during its event loop to check if it needs to 
refresh some data (console window size) that becomes stale when the 
event (console window resize) occurs. I'm not sure if this is the best 
approach; the polling isn't expensive since I have a blocking loop 
anyway, but maybe there's a more elegant solution to registering an 
observer with the FFI.

Thanks,
Dave