Need help understanding exceptions handling from C extensions

[Jacob Repp]

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.

 

[Jacob Repp]

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.