Need help understanding exceptions handling from C extensions
 

I'm working on the test cases for my AIO extension library on windows
and I have been running into this error consistently on one of my
tests:

test_addr_lookup_name_async(ClientTest):
ArgumentError: NULL pointer given
tc_client.rb:129:in `to_s'
tc_client.rb:129:in `test_addr_lookup_name_async'

The offending line is in the rescue block:

begin
q =3D AIOQueue.new
a =3D AIOAddr.new(q)
c =3D Callback.new
n =3D 0

assert(a.is_attached?, "should be attached")
a.lookup("www.google.com", c, :lookup_complete)

5.times { n +=3D q.process(100) }

assert(c.lookups =3D=3D 1, "didn't receive lookup callback")
assert(n =3D=3D 1, "not enough contexts processed")
rescue Exception =3D> ex
puts "caught #{ex}"
end

The exception is raised from q.process which hooks directly to a C
functions and makes another function call to an internal API I
defined. In this code I have my async context handler:

case CTX_ADDR_LOOKUP:
rb_funcall(
pctx->recvr,
pctx->symbid,
1,
=20
UINT2NUM(((Address*)(pctx->pbase))->addr.sin_addr.s_addr));

I believe this is 'raising' an exception. I see in other extensions
the usage of rb_protect() etc. I am under the impression that setjmp,
longjmp is being used to simulate exceptions in ruby, of which I'm
unfortunately not an expert in the usage.

I would like to be able to call out to ruby code without losing my
instruction pointer so that I may deliver the error to a registered
async error facility.

If someone could smack me over the head with a clue-by-four right now
that would be most appreciated ;)

Of course I will continue learning and experimenting but I thouht this
would be a good time to solicit the knowledge of ruby-talk.

Re: Need help understanding exceptions handling from C extensions
 

I caught the exception using rb_protect() but there is still a problem:

rbaio.c(1279): ruby error: NoMethodError: ???
rbaio.c(1292): from tc_client.rb:125:in `process'
rbaio.c(1292): from tc_client.rb:125:in `test_addr_lookup_name_async'

The class name I can interpret okay but when I take $! and call the
to_s method on it I get another exception because of the NULL issue. I
don't yet know why that is the case.

lasterr =3D rb_gv_get("$!");

// class and message
klass =3D rb_class_path(CLASS_OF(lasterr));
//message =3D rb_obj_as_string(lasterr);
DBG2("ruby error: %s: %s", RSTRING(klass)->ptr,
"???");//RSTRING(message)->ptr);

Uncommenting the conversion to string results in the NULL error.

On 2/20/06, Jacob Repp <jacobrepp@gmail.com> wrote:
> I'm working on the test cases for my AIO extension library on windows
> and I have been running into this error consistently on one of my
> tests:
>
> test_addr_lookup_name_async(ClientTest):
> ArgumentError: NULL pointer given
> tc_client.rb:129:in `to_s'
> tc_client.rb:129:in `test_addr_lookup_name_async'
>
> The offending line is in the rescue block:
>
> begin
> q =3D AIOQueue.new
> a =3D AIOAddr.new(q)
> c =3D Callback.new
> n =3D 0
>
> assert(a.is_attached?, "should be attached")
> a.lookup("www.google.com", c, :lookup_complete)
>
> 5.times { n +=3D q.process(100) }
>
> assert(c.lookups =3D=3D 1, "didn't receive lookup callback")
> assert(n =3D=3D 1, "not enough contexts processed")
> rescue Exception =3D> ex
> puts "caught #{ex}"
> end
>
> The exception is raised from q.process which hooks directly to a C
> functions and makes another function call to an internal API I
> defined. In this code I have my async context handler:
>
> case CTX_ADDR_LOOKUP:
> rb_funcall(
> pctx->recvr,
> pctx->symbid,
> 1,
>
> UINT2NUM(((Address*)(pctx->pbase))->addr.sin_addr.s_addr));
>
> I believe this is 'raising' an exception. I see in other extensions
> the usage of rb_protect() etc. I am under the impression that setjmp,
> longjmp is being used to simulate exceptions in ruby, of which I'm
> unfortunately not an expert in the usage.
>
> I would like to be able to call out to ruby code without losing my
> instruction pointer so that I may deliver the error to a registered
> async error facility.
>
> If someone could smack me over the head with a clue-by-four right now
> that would be most appreciated ;)
>
> Of course I will continue learning and experimenting but I thouht this
> would be a good time to solicit the knowledge of ruby-talk.
>
>