Andrew,

 >>> So I have a nagging bad feeling about this one.  The code of this 
function
>>> was copied from _gvariant_valid_signature.  So changing this strongly
>>> implies changing _gvariant_valid_signature as well...
>>
>> So _gvariant_valid_signature is used in two places in ell, one is
>> _gvariant_builder_enter_struct where we want to check for a sequence
>> of dbus types like in a message signature, so yes, it should accept an
>> empty string.  The other place is unit/test-gvariant-util.c where
>> we're trying to validate a single data type signature so the current
>> logic is ok.  I'll change the unit test to do "valid =
>> (_gvariant_num_children(test->signature) == 1)" instead, and add a
>> struct unit test...
>
> I was wrong here, apparently the unit test also tests for "message
> signature" type of signatures.  Why are we then treating "" as
> invalid?
>

In theory treating "" as invalid is intended behavior.  See how 
_dbus_valid_signature is used.  However, I don't think we ever tested 
empty structs, so feel free to change this.

Regards,
-Denis