/// Canvas.hpp

#include <iostream>;

class Canvas
{
    static Canvas* Create();

    std::string Foo();

    std::string Bar();
};



/// Canvas.cpp

#include "Canvas.hpp"

#include <iostream>

Canvas* Canvas::Create()
{
    return new Canvas();
}

std::string Canvas::Foo()
{
    return "Foo";
}

std::string Canvas::Bar()
{
    return "Bar";
}



/// main.d

import std.stdio;

extern(C++)
{
    class Canvas
    {
        @disable this();

        static Canvas Create();

        string Foo();

        string Bar();
    };
}

void main()
{
	Canvas canvas = Canvas.Create();

	writeln(canvas.Foo());

	writeln(canvas.Bar());
}



# clang++ -I./include/ -fPIE -c src/Canvas.cpp
# dmd source/main.d Canvas.o -L-lstdc++ && ./main
/usr/bin/ld: main.o:(.data._D4main6Canvas6__vtblZ+0x0): undefined reference to `Canvas::Foo()'
/usr/bin/ld: main.o:(.data._D4main6Canvas6__vtblZ+0x8): undefined reference to `Canvas::Bar()'
collect2: error: ld returned 1 exit status
Error: linker exited with status 1

I changed string to basic_string.

///  source/main.d
import std.stdio;
import core.stdcpp.string;

extern(C++)
{
    class Canvas
    {
        @disable this();

        static Canvas Create();

        basic_string!ubyte Foo();

        basic_string!ubyte Bar();
    };
}

void main()
{
	Canvas canvas = Canvas.Create();

	writeln(canvas.Foo());

	writeln(canvas.Bar());
}

Error ...

# dmd source/main.d Canvas.o -L-lstdc++ && ./main
[1]    49078 segmentation fault  ./main

On Monday, 13 July 2020 at 09:34:35 UTC, zoujiaqing wrote:
> # dmd source/main.d Canvas.o -L-lstdc++ && ./main
> [1]    49078 segmentation fault  ./main

On my computer I got this warning out of the compiler:

libstdc++ std::__cxx11::basic_string is not yet supported; the struct contains an interior pointer which breaks D move semantics!


sounds like it might be a known limitation.

On Monday, 13 July 2020 at 12:57:52 UTC, Adam D. Ruppe wrote:
> On Monday, 13 July 2020 at 09:34:35 UTC, zoujiaqing wrote:
>> # dmd source/main.d Canvas.o -L-lstdc++ && ./main
>> [1]    49078 segmentation fault  ./main
>
> On my computer I got this warning out of the compiler:
>
> libstdc++ std::__cxx11::basic_string is not yet supported; the struct contains an interior pointer which breaks D move semantics!
>
>
> sounds like it might be a known limitation.

Thanks Adam, but D link to C++ very hard?

On Monday, 13 July 2020 at 09:34:35 UTC, zoujiaqing wrote:
> I changed string to basic_string.
>
> ///  source/main.d
> import std.stdio;
> import core.stdcpp.string;
>
> extern(C++)
> {
>     class Canvas
>     {
>         @disable this();
>
>         static Canvas Create();
>
>         basic_string!ubyte Foo();
>
>         basic_string!ubyte Bar();
>     };
> }
>
> void main()
> {
> 	Canvas canvas = Canvas.Create();
>
> 	writeln(canvas.Foo());
>
> 	writeln(canvas.Bar());
> }
>
> Error ...
>
> # dmd source/main.d Canvas.o -L-lstdc++ && ./main
> [1]    49078 segmentation fault  ./main

Putting std::string support aside there is another issue in this example. D has virtual by default semantic unlike C++.

One possible segfault reason is that because it tries to call non existing virtual method.

Marking those D methods 'final' should fix linking issues. Also I can't remember if extern(C++) is implicitly propagated to class methods so I would put extern(C++) in class body just to be sure.

On Monday, 13 July 2020 at 16:17:55 UTC, zoujiaqing wrote:
> On Monday, 13 July 2020 at 12:57:52 UTC, Adam D. Ruppe wrote:
>> On Monday, 13 July 2020 at 09:34:35 UTC, zoujiaqing wrote:
>>> # dmd source/main.d Canvas.o -L-lstdc++ && ./main
>>> [1]    49078 segmentation fault  ./main
>>
>> On my computer I got this warning out of the compiler:
>>
>> libstdc++ std::__cxx11::basic_string is not yet supported; the struct contains an interior pointer which breaks D move semantics!
>>
>>
>> sounds like it might be a known limitation.
>
> Thanks Adam, but D link to C++ very hard?

Can you try passing -D_GLIBCXX_USE_CXX11_ABI=0 to g++ and -version=_GLIBCXX_USE_CXX98_ABI to dmd.

That comes from: https://dlang.org/changelog/2.088.0.html#std_string

C++11 ABI is currently not supported.

On 2020-07-14 05:33, Boris Carvajal wrote:

> Can you try passing -D_GLIBCXX_USE_CXX11_ABI=0 to g++ and -version=_GLIBCXX_USE_CXX98_ABI to dmd.
> 
> That comes from: https://dlang.org/changelog/2.088.0.html#std_string
> 
> C++11 ABI is currently not supported.

I based on previous messages and the usage of Clang, I think zoujiaqing is using a Mac. On Mac libc++ is used. That above might not apply.

-- 
/Jacob Carlborg