From: Jacob Repp <jacobrepp@...>
Date: 2006-02-21T16:33:28+09:00
Subject: 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 = rb_gv_get("$!");

    // class and message
    klass = rb_class_path(CLASS_OF(lasterr));
    //message = 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 = AIOQueue.new
>             a = AIOAddr.new(q)
>             c = Callback.new
>             n = 0
>
>             assert(a.is_attached?, "should be attached")
>             a.lookup("www.google.com", c, :lookup_complete)
>
>             5.times { n += q.process(100) }
>
>             assert(c.lookups == 1, "didn't receive lookup callback")
>             assert(n == 1, "not enough contexts processed")
>         rescue Exception => 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.
>
>