Error when using function in recon_trace.calls


I have an app that is printing the following error every 2 or 3 seconds:

=ERROR REPORT==== 14-Jun-2019::14:31:35.089496 ===
Unexpected message: {#Ref<0.2607974300.3493068808.175359>,badarg}

I want to find out it’s source.


To catch the process responsible, I am using recon_trace the following way (an example follows):

:recon_trace.calls({:system_information, :handle_info, fn({_ref, :badarg}, _state) -> :ok end}, 10)

However this is failing with the following error:

:recon_trace.calls({:system_information, :handle_info, fn({_ref, :badarg}, _state) -> :ok end}, 10)
Error: dbg:fun2ms requires fun with single variable or list parameter
** (CaseClauseError) no case clause matching: {:error, :transform_error}
    (recon) src/recon_trace.erl:494: :recon_trace.validate_tspec/3
    (recon) src/recon_trace.erl:424: :recon_trace."-trace_calls/3-lc$^0/1-0-"/2
    (recon) src/recon_trace.erl:426: :recon_trace.trace_calls/3

I am quite confused here. My interpretation of the documentation suggests this should be possible, based on the following sample (in erlang):

All calls to iolist_to_binary/1 made with a binary as an argument already (kind of useless conversion!): recon_trace:calls({erlang, iolist_to_binary, fun([X]) when is_binary(X) -> ok end}, 10)


What am I doing wrong?

You need to match on a list of argument in your match func. Similar to how you would specify a list in a MFA tuple.


Back at a computer rather than a mobile:

:recon_trace.calls({:system_information, :handle_info, fn [{_ref, :badarg}, _state]) -> :ok end}, 10)

This might work…

1 Like

Like this?

:recon_trace.calls({:system_information, :handle_info, fn([{ref, :badarg}, _state]) when is_reference(ref) -> :ok end}, 10)

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Yupp, as I edited it into my post seemingly at the same moment you posted as well :wink: