[erlang-questions] Sharing resource types between NIFs

Sverker Eriksson sverker.eriksson@REDACTED
Mon Feb 17 14:56:30 CET 2014

Having dependences between NIF modules (or drivers) on the native code 
level is not supported.
How symbols are resolved (or not) between dynamic libraries is OS 
dependent (Windows).
The runtime system can not keep track of such dependencies. For example,
if module B makes a native call to a function in module A and module A 
has been unloaded...VM crash (or worse).

I suggest you merge your dependent NIF code into one module. You can 
still have different modules on Erlang level and have them call a 
backend NIF module.

That being said... ... the scenario you describe should work in current 
implementation. enif_get_resource() does not care where it is called from.

/Sverker, Erlang/OTP

On 02/15/2014 11:22 PM, Loïc Hoguin wrote:
> Hello,
> I have been looking into this and after looking into the source it 
> doesn't seem possible, but I might as well ask just in case.
> Say I am writing bindings for a big library. That library is cut into 
> various components, and I would like to do similar on the Erlang side. 
> Components are more or less dependent. Let's just say that component B 
> uses component A. You can't do anything in B without A. They are both 
> NIF resources pointing to things used by the library.
> Now if I try to create a NIF module for A and a NIF module for B, I 
> need to access the resource type of A from the B NIF. I tried simply 
> exporting a function from the A .so and use it from the B .so, the 
> function returns the resource type as expected, however using it to 
> retrieve the resource fails.
> Trying to do the same from A of course works. It's just trying to use 
> the resource type of A from B that fails.
> I'm assuming this isn't possible?
> Thanks.

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