[Octave-bug-tracker] [bug #47712] libmng no longer builds under mxe-octave

[John W. Eaton]

Follow-up Comment #20, bug #47712 (project octave):

We're not talking about two random processes.  We're talking about the two
processes in a shell command list "A && B".  For that, the process A must exit
before B starts, correct?  And when a process exits, aren't pending writes
supposed to be flushed and open files closed?  Shouldn't that all happen
before the exit status is returned to the shell?  If so, then how can any file
written by A NOT be available to B unless there is a filesystem or OS bug?  If
there is no such guarantee, then I'm amazed that any automake-generated
Makefile functions properly since they are full of shell command lists just
like this.

If there is some delay before a file created by process A is available to
process B, then I would expect random failures to be happening all the time. 
And if there is no guarantee "A && B", then I see no reason to expect "A; B"
to work either.  Or for a series of commands in a Makefile recipe to work
reliably, even if each line is executed in a separate subshell.  How could we
know when a file might be flushed and ready to read by another process?

If I'm wrong about all of this, then please point me to some docs or code or
textbook or something that explains and warns that there is no guarantee.

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