extern(C++, ns)

[Manu via Digitalmars-d]

On 3 January 2016 at 15:45, Manu <turkeyman at gmail.com> wrote:

> On 3 January 2016 at 15:34, Rikki Cattermole via Digitalmars-d <
> digitalmars-d at puremagic.com> wrote:
>
>> On 03/01/16 6:26 PM, Manu via Digitalmars-d wrote:
>>
>>> On 3 January 2016 at 15:17, Rikki Cattermole via Digitalmars-d
>>> <digitalmars-d at puremagic.com <mailto:digitalmars-d at puremagic.com>>
>>> wrote:
>>>
>>>     Ok, so what I gathered from that is that if a D package/module
>>>     matches a C++ one in scope, D will only be checked.
>>>
>>>
>>> No, you name conflict error. But that's not the main problem I'm talking
>>> about, which is that namespace scopes are created and break everything.
>>>
>>>     The obvious answer would be to rename the D side, but that really
>>>     isn't good enough.
>>>
>>>
>>> You don't just go and rename an entire existing project, which is a lib
>>> in this case (so, also rename all the clients...?) because you need to
>>> type extern(C++) somewhere :/
>>>
>>
>> Hang on I just tried this on Windows:
>>
>> module ns.m;
>>
>> import x.y;
>> // import x.y : ns.Y; // doesn't work grr
>> import x.y : Y;
>>
>>
>> module x.y;
>>
>> extern(C++, ns) {
>>         struct Y {
>>         }
>> }
>>
>>
>> Does this work for you?
>>
>
> The short answer is, "most of the time".
> I've been using recursive modules to place extern(C++) declarations in a
> sensible scope quite a lot. It breaks sometimes, not sure why... suspect
> it's related to forward referencing, or multiple/semi-circular imports.
>

For instance, connecting to the C++ string lib:

module libep.string;
public import libep.c.string : BaseString, MutableString, SharedString;
alias String = BaseString!char;
alias WString = BaseString!wchar;
alias DString = BaseString!dchar;

Those don't like to be imported that way: Error: template instance
BaseString!char BaseString is not a template declaration, it is a alias
If I instead:

module libep.string;
static import libep.c.string;
alias BaseString = libep.c.string.BaseString;
alias MutableString = libep.c.string.MutableString;
alias SharedString = libep.c.string.SharedString;
alias String = BaseString!char;
alias WString = BaseString!wchar;
alias DString = BaseString!dchar;

That works in this case. Other cases are different, eg:

module libep.variant;
public import libep.c.variant : Variant;

That one works.
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