[erlang-questions] Passing a digraph between processes on the same node

[Steve Davis]

Ouch. OK, I totally see it. 

tysm Mr. V!


> On Jun 9, 2015, at 7:55 PM, Steve Vinoski <vinoski@REDACTED> wrote:
> 
> 
> On Tue, Jun 9, 2015 at 7:55 PM, Steve Davis <steven.charles.davis@REDACTED <mailto:steven.charles.davis@REDACTED>> wrote:
> Hi,
> 
> Somehow I’m not seeing why the following fails:
> 
> -module(gtest).
>  
> -export([test/0]).
>  
> test() ->
>                 Test = self(),
>                 spawn(fun() -> graph(Test) end),
>                 receive
>                 {ok, G} ->
>                                 digraph:vertices(G)
>                 after 5000 ->
>                                 timeout
>                 end.
>  
> graph(Pid) ->
>                 G = digraph:new(),
>                 digraph:add_vertex(G),
>                 Pid ! {ok, G}.
> 
> …since the backing ets table is “protected" by default, shouldn’t the calling process be able to read the values set by the process that builds the digraph?
> 
> The process running graph/1 is the owner of the ets tables. It dies as soon as the graph/1 function completes and it takes the ets tables down with it.
> 
> Add two calls to ets:i/0, one right after receiving {ok,G} and the other right after the digraph:new/0 call, then run gtest:test/0 from the shell and you'll see that the digraph-related ets tables disappear by the time the receive handles the message.
> 
> --steve

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