[erlang-questions] Trace erlang BIFs with dbg

Dmytro Lytovchenko <>
Sat Sep 10 12:59:36 CEST 2016

There is a known problem observed in unreleased Erlang R20, that I am
working to have fixed soon, and the sympthoms are that some BIFs do not
send trace messages for returns and exceptions. Some other BIFs do, though.
I can not say when this problem appeared first, but it could be present in
R19. Possibly related to recent changes in tracing.

This is fundamental problem (SOME execution paths of some BIFs do not have
trace checks/reports in them), and i am on it.

lör 10 sep. 2016 kl 00:38 skrev nato <>:

> Are BIFs such as `length/1` part of the erlang module, or do BIFs live
> somewhere else then get masqueraded ...
> I am trying to trace functions like these with dbg, and nothing is yielded.
> For example, I am trying the following with no success...
> 1> dbg:tracer(), dbg:p(all, c).
> 2> dbg:tpl(erlang, length, x).
> 3> erlang:length( [] ). %% or simply `length([]).`
> Or, are my above dbg flags leaving the erlang module out... or... confused.
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