Drawbacks of using declarations/namespace aliases

[Stephan Bergmann]

On 12/12/2012 03:22 PM, Lubos Lunak wrote:
> On Tuesday 11 of December 2012, Stephan Bergmann wrote:
>>> commit 3e64874e7cd234ff563ac11450cfb2b6e2db4bf6
>>> Author: Radu Ioan <ioan.radu.g at gmail.com>
>>> --- a/configmgr/source/access.hxx
>>> +++ b/configmgr/source/access.hxx
>>> @@ -82,7 +82,6 @@ namespace com { namespace sun { namespace star {
>>>        }
>>>        namespace util { struct ElementChange; }
>>>    } } }
>>> -namespace rtl { class OUString; }
>>
>> Changes like this are, strictly speaking, unsound.  They rely on at
>> least one of the included headers happening to in turn include
>> rtl/ustring.hxx.
>
>   Which, practically speaking, is pretty much guaranteed to happen for
> OUString.
>
>> The underlying intransparency wrt forward declarations is IMO a
>> fundamental drawback of the recent efforts of beautification via using
>> declarations or namespace aliases, for rtl and com::sun::star.
>
>   I don't understand what fundamental drawback you mean.

The drawback that you must either break transparency when using forward 
declarations (by explicitly mentioning "namespace rtl { ... }" resp. 
"namespace com { namespace sun { namespace star { ... } } }") or use 
#includes instead of forward declarations (which increases dependencies 
and thus needles recompilations; arguably not much of an issue for the 
rtl::OUString etc. case, but potentially an issue for the com::sun::star 
case).

Stephan