libxrdeveloper's documentation
void xr_call_set_retval ( xr_call call,
xr_value val 
)

Set return value of the XML-RPC call.

Parameters
callCall obejct.
valRetuirn value node. Call object takes ownership of this value and xr_value_unref will be called from xr_call_free.
Documentation for libxr, Tue Nov 10 2015 00:41:31.