[9fans] rc exec error behaviour

[cinap_lenrek@felloff.net]

in the rc shell, when one has exec statement and the exec fails, rc tries to
continue interpreting statements after the exec which fails with a strange
EOF error because in the process of preparing filedescriptors for exec,
the very fd thats used to read the script was closed.

burnzez provided an example of this like:

term% rc -c 'exec doesnotexist; echo test'
doesnotexist: './doesnotexist' directory entry not found
test
rc: /rc/lib/rcmain:29: token EOF: syntax error

the manpage does not explicitely specify what should happen when exec fails.

i did try to have rc open the . script as OCEXEC and that fixed the
problem, but it wont work for any other redirections and will have side effects
as the close-on-exec flag is a propery of the channel and not of the file
descriptor slot. so imagine stuff like . /fd/0...

i think it would me most resonable to just have rc exit with error status on
failure. are there any objections to this?

--
cinap