Re: enif_make_double returns invalid term for 'nan'
Mikael Pettersson <[email protected]>
| Newsgroups | gmane.comp.lang.erlang.bugs |
|---|---|
| Message-ID | <[email protected]> |
Heinz Nikolaus Gies writes:
> When enif_make_double gets a nan value passed as the double argument it returns a invalid term, this term can neither be printed (via the fmt*) functions nor can it be deserialized by binary_to_term when serializing it the following binary is generated:
>
> 6> io:format("~p~n", [term_to_binary(V)]).
> <<131,99,110,97,110,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0>>
>
> V is the double returned by enif_make_double
There are two issues here:
1. the VM disallows INFs and NANs, but NIF authors may not be aware of that
2. enif_make_double() SHOULD reject non-finite doubles but it doesn't, and
its documentation doesn't mention any failure modes; returning THE_NON_VALUE
may not be detected as a failure by the NIF and so this non-value may leak
into aggregates (lists or tuples) where it will totally break things
When looking at this I noticed that enif_make_atom() also has problems: it
may fail and return THE_NON_VALUE if the resulting atom would be too long,
but the documentation doesn't mention this possibility so the NIF might
continue and store this non-value in aggregates before returning.
The OTP folks need to straighten up error handling in the enif_make_*()
functions.
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