[erlang-bugs] internal compiler faults

Björn Gustavsson <>
Fri Dec 11 16:38:35 CET 2009

On Fri, Dec 11, 2009 at 3:20 PM, Simon Cornish <> wrote:

> I fail to see how this minimisation helps the discussion. The point of
> including both the yes/3 and bad/3 functions was to show that only one
> of the two different methods of calculating Do1 & Do2 caused the
> crash. I would have thought this would help point to the underlying
> optimisation error.

It helped me. I generally debug optimization problems
by printing out and inspecting the internal data structures,
so the smaller the better. Having different versions to
compare can be useful, however, when I have located
the problem and I need to decide the best way to solve it.

> Regarding the internal consistency check, I used the beam_bool patch
> and still encountered the same problem. Attached is a small example.
> It will compile if no_bopt is used. It will also compile if the
> boolean guard is not repeated (eg. CH2 is assigned a constant value).

Thanks! That information gives me a pretty good idea
where I should start looking for the problem.

Björn Gustavsson, Erlang/OTP, Ericsson AB

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