I can successfully run the cerl -debug vm from the sym link:
root@:~# erts-11.2.2.15/bin/cerl -debug
Erlang/OTP 23 [erts-11.2.2.15] [source] [64-bit] [smp:12:12] [ds:12:12:10]
[async-threads:1] [hipe] [type-assertions] [debug-compiled] [lock-checking]
Eshell V11.2.2.15 (abort with ^G)
1>
On Monday, August 22, 2022 at 10:17:39 AM UTC-7 Stephen Baldwin wrote:
> Hey José,
>
> I was able to get elixir to work with cerl, such as elixir -e "IO.puts
> :ok". But I could not get it to work in the release environment running in
> docker. I get this error:
>
> root:~# releases/0.1.0/elixir -e "IO.puts :ok"
> {"init terminating in
> do_boot",{undef,[{elixir,start_cli,[],[]},{init,start_em,1,[]},{init,do_boot,3,[]}]}}
> init terminating in do_boot
> ({undef,[{elixir,start_cli,[],[]},{init,start_em,1,[]},{init,do_boot,3,[]}]})
>
> Crash dump is being written to: erl_crash.dump...done
>
> In my dockerfile I replace the elixir bin with my elixir debug like so:
>
> ....
> COPY --from=build /app/_build/prod/rel/app ./
> # Copy erlang source, along with erlang debug binary
> COPY --from=build /OTP/subdir /OTP/subdir
> # Symlink erlang debug binary to erts bin dir
> RUN ln -s /OTP/subdir/bin/cerl
> /app/releases/0.1.0/../../erts-11.2.2.15/bin/cerl
> # Replace elixir script with our scrip that runs the erlang debug binary
> COPY elixir-debug releases/0.1.0/elixir
> RUN chmod +x releases/0.1.0/elixir
> ...
>
> The source image for my app docker file
> is hexpm/elixir:1.10.4-erlang-23.3.4.16-ubuntu-bionic-20210930 but modified
> to keep the erlang source code and build cerl debug vm.
>
> I don't think I can reasonably share a minimal app that reproduces the
> issue (without sharing my app code which I cannot). The seg fault happens
> randomly after x hours and I do not know what is causing it.
>
> Attached is my modified elixir bin.
>
>
> On Monday, August 22, 2022 at 9:14:52 AM UTC-7 José Valim wrote:
>
>> Or perhaps please provide a minimal app that reproduces it. :)
>>
>> On Mon, Aug 22, 2022 at 6:13 PM José Valim <jose....@dashbit.co> wrote:
>>
>>> Running Elixir with cerl should just work. Can you expand on the on_boot
>>> errors you get in a release?
>>>
>>> On Mon, Aug 22, 2022 at 5:46 PM Stephen Baldwin <
>>> stephen...@syncromsp.com> wrote:
>>>
>>>> Hello I've been trying to debug a seg fault in my elixir app for a bit.
>>>> I've learned that if debugging symbols are enabled on the erlang vm you
>>>> can
>>>> use gdb to debug a linux core file to deduce where the seg fault is
>>>> occuring. Now I've rebuilt erlang from source to have the debugging
>>>> symbols
>>>> and that all works fine, but using it with an elixir release seems to be a
>>>> bit difficult.
>>>>
>>>> I modified the elixir bin similar to
>>>> https://github.com/elixir-lang/elixir/pull/11082 but I am getting
>>>> on_boot errors when running the release. So replacing cerl with erl isn't
>>>> a
>>>> path to success.
>>>>
>>>> I need some help as I don't fully understand the path from an elixir
>>>> release to the erlang vm. Any quick ways to get this to work? Otherwise I
>>>> think it would be worthwhile to have an option when building an elixir
>>>> release to use a cerl vm (debug, valgrind, etc).
>>>>
>>>> Regards,
>>>> Stephen
>>>>
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>>>>
>>>
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