[erlang-questions] Strange behaviour of atoms in NIF

Sverker Eriksson sverker@REDACTED
Thu Sep 15 12:32:13 CEST 2011

Dmitry Groshev wrote:
> I'm writing a NIF-based circular array library and experiencing a strange 
> behaviour of atoms in there. I have a NIF that should return an atom. It's 
> fairly simple, but I get different atoms when calling this NIF from 
> different places. Here is an issue with quite comprehensive explanation, 
> please take a look at it at github: 
> https://github.com/band115/ecirca/issues/31 I've tried to compare atoms that 
> are returned by printf'ing them, but they seems identical in despite of 
> obvious difference in shell.
NIF debugging tip #1:

int erts_printf(const char *, ...);

Works the same as printf with the additional feature of %T to print 
Is not part of the official API (yet) and does therefore not work on 

NIF debugging tip #2:

Use debug compiled emulator.

> cd $ERL_TOP/erts/emulator
> make FLAVOR=smp debug       (or FLAVOR=plain)
> $ERL_TOP/bin/cerl -debug

/Sverker, Erlang/OTP Ericsson

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