tuesday, 12 june 2007

posted at 15:38
tags:

I started writing an entry about Open() and its edge cases this morning, but it made very little sense, which I suppose is fitting. I got to the end of the day just now, and read back over it, and decided that it was dumb. My brain is mushy anyway after the madness of today, so I'm not going to go into it much.

In short, Open() works like you'd expect (turn a name into a filehandle) except when you call it with an empty name, which makes it open a file using a lock in pr_CurrentDir, unless you're on AROS where handles and locks are the same thing, and then it duplicates a handle. Since the mode flags are taken into account, its not a pure duplication, yet its called on the original object, so the semantics are slightly different to just opening the file again with its original name. This subtlety is why pipes are currently broken.

Further, FSA_OPEN (the IOFS action underneath Open()) with a filename of "/" actually means "open the parent directory", ie ACTION_PARENT under the packet system. Our console handler didn't know this, causing More IN: to crash the system.

I'll shortly decide on the One True Way, and fix everything. Technically its an API break, but this is a non-trivial corner case and it needs to be fixed - its not something that will break most (all) existing programs.