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Re: return value of prop_*_recv_syscall()
On 24.09.2011 22:35, Francois Tigeot wrote:
While learning how to use proplib, I've found an inconsistency between the
documentation and the actual kernel implementations:
the manual page for prop_array_send_syscall, prop_array_recv_syscall,
prop_dictionary_send_syscall and prop_dictionary_recv_syscall says these
functions return true if successful
The kernel implementations are different for prop_array_recv_syscall() and
prop_dictionary_recv_syscall, they return 0 if there's no error:
Since DragonFly's proplib implementation comes from NetBSD, I figured it
would be best to ask here what to do:
fix the documentation or fix the implementation ?
Hmm, good question; it seems that the API has not been designed
prop_*_recv_syscall() are used as if they returned an int that indicates
"no error" (0) or error (!= 0). They capture the return value of
However, prop_*_send_syscall() do it differently: being an alias for
prop_*_externalize_to_pref(), they return a boolean, and set errno to
the correct value in case the result is "false".
I believe the API needs to be consistent; one way to do that is to have
a prop_*_internalize_from_pref() similar to prop_*_externalize_to_pref()
 that returns a boolean and set errno to the error value, and use
these for recv_syscall via __strong_alias().
return (_prop_object_internalize_from_pref(blah) == 0);
in prop_kern.c should be enough to fix it, but I'm not sure if this is the
better idea in the long run ...
IMHO, it's not: we are losing a way to report the type of error
encountered in case there is one.
I would suggest to contact Manuel Bouyer directly, I think he is the one
that designed the API.
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