[erlang-bugs] Trace bug?

[Lukas Larsson]

Hello Mikael,

You can find the fix here: 
https://github.com/garazdawi/otp/commit/df0fb5553149aa75ad7b6f2df0802675ae25cd19

Lukas
On 04/06/14 13:12, Mikael Pettersson wrote:
> Lukas Larsson writes:
>   > Hello Robert and Tony,
>   >
>   > Thanks for reporting and tracking this down. It seems to be a bug that
>   > was introduced in R16B.
>   >
>   > I've written a fix for it that probably will be part of Erlang/OTP 17.1.
>
> Do you have a pointer to this fix?  We need to backport it to R16B.
>
> /Mikael
>
>   >
>   > Lukas
>   >
>   > On 02/06/14 17:11, Tony Rogvall wrote:
>   > > in bif.c:1885 (r17)
>   > >
>   > > The code will only call the trace_send function if the name is NOT registered.
>   > > Not sure how nor why.
>   > >
>   > > When NO process is registered to x (yield badarg)
>   > >
>   > >> erlang:trace(spawn(fun() -> x ! message end), true, [send]).
>   > > 2> flush().
>   > > Shell got {trace,<0.45.0>,send,message,x}
>   > > ok
>   > >
>   > > When process is registered to x:
>   > >
>   > > register(x, self()).
>   > >> erlang:trace(spawn(fun() -> x ! message end), true, [send]).
>   > > 1
>   > > 11> flush().
>   > > Shell got message
>   > > ok
>   > >
>   > > Feature?
>   > >
>   > > ;-)
>   > >
>   > > /Tony
>   > >
>   > >
>   > > On 2 jun 2014, at 16:50, Robert Virding <rvirding@REDACTED> wrote:
>   > >
>   > >> No, answers?
>   > >>
>   > >> Robert
>   > >>
>   > >>
>   > >>
>   > >> On 30 May 2014 23:18, Robert Virding <rvirding@REDACTED> wrote:
>   > >> Can anyone tell me if this is a bug? If not how do I get around it in simple way?
>   > >>
>   > >> Robert
>   > >>
>   > >>
>   > >>
>   > >> On 27 May 2014 17:45, Robert Virding <rvirding@REDACTED> wrote:
>   > >> We have discovered strange behaviour when tracing message sends. We turn on tracing message send for a process. In R16 and 17 it seems like there is no trace message when sending to a registered process name, while sending to a pid generates a trace message as it should. In R15 however you get a trace message both sending to a registered name and hen sending to a pid. Is this a bug or is it a new undocumented feature?
>   > >>
>   > >> As an example I include simple program in which worker sends a message to a registered server and the server replies by sending the worker pid. Here are outputs when running in 17:
>   > >>
>   > >> Erlang/OTP 17 [erts-6.0] [source-07b8f44] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]
>   > >>
>   > >> Eshell V6.0  (abort with ^G)
>   > >> 1> c(trace_procs).
>   > >> {ok,trace_procs}
>   > >> 2> trace_procs:start().
>   > >> trace_procs 7 Server: '<0.39.0>'
>   > >> trace_procs 10 Worker: '<0.40.0>'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,answer,<0.40.0>}'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,answer,<0.40.0>}'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,answer,<0.40.0>}'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,answer,<0.40.0>}'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,answer,<0.40.0>}'
>   > >>
>   > >> and in R15:
>   > >>
>   > >> Erlang R15B03 (erts-5.9.3.1) [source] [64-bit] [smp:4:4] [async-threads:0] [hipe] [kernel-poll:false]
>   > >>
>   > >> Eshell V5.9.3.1  (abort with ^G)
>   > >> 1> c(trace_procs).
>   > >> {ok,trace_procs}
>   > >> 2> trace_procs:start().
>   > >> trace_procs 7 Server: '<0.38.0>'
>   > >> trace_procs 10 Worker: '<0.39.0>'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,{request,<0.39.0>},server}'
>   > >> trace_procs 34 Message: '{trace,<0.38.0>,send,answer,<0.39.0>}'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,{request,<0.39.0>},server}'
>   > >> trace_procs 34 Message: '{trace,<0.38.0>,send,answer,<0.39.0>}'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,{request,<0.39.0>},server}'
>   > >> trace_procs 34 Message: '{trace,<0.38.0>,send,answer,<0.39.0>}'
>   > >> trace_procs 34 Message: '{trace,<0.39.0>,send,{request,<0.39.0>},server}'
>   > >>
>   > >> What gives?
>   > >>
>   > >> Robert
>   > >>
>   > >>
>   > >>
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