Martin Pala <address@hidden> writes:
I tried to find some way to solve uid and gid problem to allow its
usage as standalone statement in addition to its usage in exec
statement. I think the change of the uid and gid ('useroption') will
involve too much extra code (present version is very simple and
effective, but restricted to predefined usage).
We can keep present simplicity by renaming 'uid' and 'gid' options in
exec statements to 'euid' and 'egid' (which is exactly what it in fact
is) => 'uid' and 'gid' tokens will be freed for its own statement
usage (which again is in fact what it is - real owner and group).
A much better solution is to do a small grammer change. This will
further break backward compability, but it will make life MUCH MUCH
easier for us now and in the future. The solution is to promote IF and
THEN to real keywords (maybe also ELSE for future use).
By using IF and THEN the parser can use its one lookahead to deduce if
it should reduce or shift. Thus we can avoid all the shift/reduce
problems we experience today when we reuse keywords in different
statements. A great benefit by using IF/THEN is also that some
statements can be written with a default action and with an action
option. For instance with the current grammar the following example
using the port statement will not work as I explained before because
of the reduce and shift problem. In the current grammar we must choose
either to use (1) or (2) because both cannot be used in the same grammar.
(1) | host port type protocol connecttimeout { default action }
(2) | host port type protocol connecttimeout action { user select action }
But here comes the clever part, by using IF and THEN as keywords both
statements may be used in the same grammar without generating a
shift/reduce error:
| IF host port type protocol connecttimeout
| IF host port type protocol connecttimeout THEN action
And your UID/GID statement will work perfectly without any
shift/reduce errors also, for instance this will work:
| IF UID NOTEQUAL STRING
| IF GID NOTEQUAL STRING
| IF UID NOTEQUAL STRING THEN action
| IF GID NOTEQUAL STRING THEN action
I have tested this in my local p.y grammar file and it works just
fine. So I suggest or actually insist :) that we promote IF/THEN/ELSE
to real keywords and rewrite our grammar to use those as outlined
above. The statements affected and in need for rewrite will be:
- port
- timestamp
- resource
- permission
- size (?)
- and your UID/GID test for files.