[erlang-questions] Improve $handle_undefined_function

Loïc Hoguin <>
Tue Jan 22 00:10:13 CET 2013

On 01/21/2013 11:15 PM, Tony Rogvall wrote:
> On 21 jan 2013, at 19:04, Loïc Hoguin <
> <mailto:>> wrote:
>> Hello,
>> Just recently the $handle_undefined_function feature was introduced.
>> It is a way to override error_handler mechanisms when a function isn't
>> found, and works per module for all processes, instead of just one.
>> Regardless of the intent behind this feature, the implementation that
>> was pushed to master is in my opinion, and apparently others, deeply
>> flawed. The main issue is that it pushes the responsability of
>> propagating the right errors directly to the user, and the user must
>> use extra care when writing this handler.
> This is strange. You think that every one should stay away from this
> feature, but then you start to play
> around with it your self. Why? Are better suited to handle this
> abomination than the rest of us or what?

I said stay away because the implementation is flawed. If this feature 
behaves the same as any other function call, then I'm perfectly good 
with it.

Loïc Hoguin
Erlang Cowboy
Nine Nines

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