Hi,
On Thu, Nov 01, 2007 at 10:40:22PM -0700, David Fifield wrote:
> Are NSE exceptions supposed to return false or nil? At
> http://insecure.org/nmap/nse/nse-api.html#nse-exceptions it says that
> the first thing returned is a Boolean value. But trying to catch an
> exception from connect fails, as the attached example script (test.nse)
> shows. It produces this message:
>
> Initiating SCRIPT ENGINE at 22:26
> false Name or service not known
> SCRIPT ENGINE: In: nse_nmaplib.cc:474 Trying to finalize a non conforming function. Are you sure you return true on success followed by the remaining return values and nil on failure followed by an error string?
> QUITTING!
>
> We see that connect returns (false, "Name or service not known"), but
> this is "non conforming." Should NSE's internal functions be modified to
> return nil instead of false, or should false be considered an exception
> marker? Does the patch I attached do the right thing?
I think the latter would be more convenient.
Since the network I/O functions return true on success I would expect a false
value to indicate an exception.
AFAIK this patch shouldn't cause any problems with the remaining NSE.
>
> David Fifield
>
>..snip..
> Index: nse_nmaplib.cc
> ===================================================================
> --- nse_nmaplib.cc (revision 6111)
> +++ nse_nmaplib.cc (working copy)
> @@ -460,7 +460,7 @@
> }
>
> static int l_exc_finalize(lua_State *l) {
> - if (lua_isnil(l, 1)) {
> + if (lua_isnil(l, 1) || !lua_toboolean(l, 1)) {
This looks good to me, however if I recall correctly the lua_isnil() is not
really needed, because lua_toboolean() should return false if there is nil
at the specified position on the stack.
> lua_pushvalue(l, lua_upvalueindex(1));
> lua_call(l, 0, 0);
> lua_settop(l, 2);
cheers
stoiko
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Received on Nov 02 2007
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