Re: Interface Ada string with C++ std::string

[Lucretia <laguest9000@googlemail.com>]

On Wednesday, 4 July 2018 12:45:30 UTC+1, Roger  wrote:
> On Wednesday, July 4, 2018 at 9:23:23 PM UTC+10, Lucretia wrote:
> 
> > All you probably need is a C function which returns the string c_str() to Ada which Ada can then use, wrap that in Ada. Just define a private type for the string class which is an address and pass that to the C function.
> > 
> > package CPP_Strings is
> >    type CPP_String is private;
> > 
> >    function Get (S : in CPP_String) return String; -- Wrap the C->Ada stuff inside here.
> > private
> >    type CPP_String is System.Address;
> > end CPP_Strings;
> 
> Thanks,
> I was playing around today modifying your test_binding code then managed to accidentally delete everything I'd done!
> I think I'll have another go at it as it is an educational experience.
> Once I've done that, I'll be in a better position to understand and implement what you've just suggested.
> Everything is pretty much in line with my thinking. My main problem is my minimal experience with C++ so your helping hand is very welcome.
> Once I found it impossible to directly interface std::string to Ada, I thought the way ahead would be to write a C interface to C++ and then wrap the C interface to Ada as you have suggested.
> My original post was due to not being sure how to do it. So your advice has been a tremendous help and makes me confident that I'll get there eventually.

The test_binding is the extreme way to do it.

The simpler, kind of, and preferred way would be to work out what you need from the string class. Pass around the C++ pointer inside Ada. Then have C functions which are imported to Ada which handle the messy C/C++ stuff, then wrap those in Ada handling the Messy Ada/C stuff there.