[Cuis-dev] Questions triggered by #forceChangesToDisk

[Andres Valloud]

Phil,

Regarding your observations on forceChangesToDisk, first a side comment. 
  That there is a method or even a primitive called 
'blah-blah-flush-blah' does not mean the function fflush()

https://pubs.opengroup.org/onlinepubs/9699919799/functions/fflush.html

or equivalent is actually called.  Assuming otherwise eventually leads 
to conclusions such as "xyzOS is so broken haha", and that's really self 
limiting.

So, with a skeptic mentality in place, what is that flush method 
actually doing?  It looks like the relevant code is this:

primFlush: id
	"Flush pending changes to the disk"
	| p |
	<primitive: 'primitiveFileFlush' module: 'FilePlugin'>
	"In some OS's seeking to 0 and back will do a flush"
	p _ self position.
	self position: 0; position: p

That primitive failure is strange indeed, plus the failure is silent so 
good luck noticing something might be off.  So, rather than seeking back 
and forth to (pretend to) deal with the failure, the question should be 
why fflush() can't do its job.  Does primitiveFileFlush actually call 
the equivalent of fflush() in all platforms?  Where and why does the 
primitive fail, exactly?  Suppose the id is stale, why does changing the 
file position improve the situation on an file that is not open?  Does 
the primitive fail because it's not implemented?  If that happens, then 
why isn't the hack of opening / closing the file done here instead, 
i.e.: why is there yet another hack that is different?  Or, why was it 
necessary to hack forceChangesToDisk, in a different way, on top of the 
hack here?  Exactly what operating systems are those "some OS's" the 
comment talks about?  Is there any evidence in support of the 
authoritative assertion that seeking causes flushing?

Andres.