[9fans] panic(?) and error(?)

[Lucio De Re <lucio@proxima.alt.za>]

I'd like some descriptions for functions error() and panic() as used
in /sys/src/cmd/9660srv/main.c and /sys/src/cmd/upas/fs/fs.c
respectively - and elsewhere, no doubt.

The arguments are different and I'm having difficulty understanding
whether they are functionally similar but retained for historical
reasons (what would be the "modern" equivalent?) or whether in fact
the choice depends on the context.

I note that 9660srv closes fds 0 and 1 and reopens them in the most
harmless manner (/dev/null), which upas/fs does not do and I wonder
if these are influencing the choice of error reporting.

Of course, I do have the source to consult, but little guidance on
where to look, even.

++L