[erlang-patches] wxe_server bug? (and patch)
Mazen Harake
mazen.harake@REDACTED
Wed Oct 14 15:25:21 CEST 2009
A quick note:
I just realized that this example doesn't work unless you have applied
my previous patch for wx_object.erl. Either apply that or change the
code to call the wx_object with the form (somehow) :)
/Mazen
Mazen Harake wrote:
> Hi,
>
> There is a situation in the wx library that causes the wxe_server to
> crash when it receives a message with a pid which is considered by
> distributed Erlang to come from another node when in fact it isn't.
> This happens when net_kernel is started explicitly (I.e. Erlang going
> into distribution mode) and an wx_object (which was created before
> net_kernel was started) is destroyed.
>
> Here is a simple example:
> Create this module:
> -module(test).
> -compile(export_all).
>
> start() ->
> wx:new(),
> wx_object:start_link({local, ?MODULE}, ?MODULE, wx:get_env(), []).
>
> close(_, _) ->
> wx_object:call(?MODULE, stop).
>
> init(Wx) ->
> wx:set_env(Wx),
> Mf = wxFrame:new(wx:null(),1,"",[{size,{300,300}}]),
> wxFrame:show(Mf),
> wxFrame:connect(Mf, close_window, [{callback, fun ?MODULE:close/2}]),
> {Mf, Mf}.
>
> handle_call(stop, _From, Mf) ->
> wxFrame:destroy(Mf),
> {stop, normal, ok, Mf}.
>
> terminate(normal, _) ->
> ok.
>
> Then run this in the shell:
> Erlang R13B (erts-5.7.1) [smp:2:2] [rq:2] [async-threads:0]
>
> Eshell V5.7.1 (abort with ^G)
> 1> c(test).
> {ok,test}
> 2> test:start().
> {wx_ref,35,wxFrame,<0.42.0>}
> 3>
>
> This should give you a small frame, don't close it yet,
> Now do this:
> 3> net_kernel:start([bad,shortnames]).
> {ok,<0.49.0>}
> (bad@REDACTED)4>
>
> Now close the frame and you should see:
> =ERROR REPORT==== 14-Oct-2009::13:17:08 ===
> ** Generic server <0.39.0> terminating
> ** Last message in was {'_wxe_destroy_',<3.42.0>}
> ** When Server state == {state,#Port<0.2605>,#Port<0.2602>,
>
> {1,{<0.32.0>,{user,[],[],undefined},nil,nil}},
> [<0.57.0>],
> {1,{#Fun<test.close.2>,1,nil,nil}},
> 2}
> ** Reason for termination ==
> ** {badarg,[{erlang,is_process_alive,[<3.42.0>]},
> {wxe_server,handle_info,2},
> {gen_server,handle_msg,5},
> {proc_lib,init_p_do_apply,3}]}
>
>
> The pid which comes from the port is not recognized as a local pid and
> thus erlang:is_process_alive/1 will exit with badarg. My question is:
> Is this a "feature" or a bug? I think this is a bug but I'm not sure
> what is expected from the wx library point of view. IMHO it shouldn't
> crash and just ignore it in this case because the wxe_server shouldn't
> be allowed to crash.
>
> Anyway I put in a patch as well just in case this is something that
> should be fixed. The patch can be applied to both wx 0.98.1 and 0.98.3.
>
> Cheers,
>
> /Mazen
>
>
>
>
> ------------------------------------------------------------------------
>
>
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