Calling C++ "void foo(Klass&)"

[Mengu via Digitalmars-d]

On Tuesday, 8 August 2017 at 21:04:23 UTC, Jacob Carlborg wrote:
> On 2017-08-08 20:51, Johan Engelen wrote:
>> Hi all,
>>    Currently, it is not possible to call the C++ function "void
>> foo(Klass&)" when Klass is an extern(C++) _class_ on the D 
>> side. You
>> have to declare Klass as a D _struct_, otherwise there is no 
>> way to get
>> the correct mangling. When Klass has virtual functions, you're 
>> hosed.
>>
>> For more context (involving "const"), see:
>> https://forum.dlang.org/post/tvohflgtaxlynpzedqky@forum.dlang.org
>>
>> Is this problem on anybody's radar?
>> What are the ideas to resolve this issue, or are we content 
>> never to
>> solve it?
>
> One way to do it, that might be a bit confusing, is to force 
> the declaration of the function to explicitly specify a pointer 
> or a reference. Currently it looks like it's an implicit 
> pointer.
>
> extern (C++) class Klass {}
> void foo(Klass*); // ok
> void foo(ref Klass); // ok
> void foo(Klass); // error
>
> Of course, there's always pragma(mangle) as well.

sorry for hijacking the thread but i have a similar question:

i was wondering if i could write a wrapper for a C++11 library 
called cpr. in one of its header files 
(https://github.com/whoshuu/cpr/blob/master/include/cpr/auth.h#L13) it has a generic constructor that initializes its member fields. i had no idea as to how to do it. then i came up with the following line:

     extern (C++, cpr) {
         this(UT, PT)(ref UT username, ref PT password) { ... }
     }

when i compiled it with the .a lib given, it worked. do you guys 
think i did it right? the &

my second question is: i have no idea what's going on in this 
file: 
https://github.com/whoshuu/cpr/blob/master/include/cpr/body.h i'd 
appreciate some pointers.