Swift and C++ bridging in Xcode

Question

error Machine info: macOS 10.13.5 Xcode 9.4 Swift 4.1 Default c++ compiler

I've created simple swift project and just added c++ file with header to it and Xcode created bridging header for me. I've initialised basic function in .cpp file, written prototype to .hpp file and included .hpp file in bridging header. When I've started typing in .swift file everything seemed to work: my cpp function name was suggested in .swift file in proper place and there were no warnings or errors. But, when I've tried to build this project, and got following: Undefined symbols for architecture x86_64: "_get", referenced from: _main in main.o

Here is source code:

    // main.swift
    import Foundation

    print("Hello, World!")

    var number = get();

    // cppBackend.cpp
    int get()
        {
        return 1;
        }

    // cppBackend.hpp
    int get();

    // test-Bridging-Header.h
    #include "cppBackend.hpp"


    //cppBackend.hpp second version
    #ifdef _cplusplus
    extern "C"
        {
    #endif


    #include <stdio.h>

    int get();

    #ifdef _cplusplu
        }
    #endif

This should help: https://stackoverflow.com/a/49406606/1187415: you have do disable "name mangling" with `extern "C"` — Martin R, Jun 07 '18 at 19:58
I mean, it is possible to use both in one project, not file. — Damirov Eldar, Jun 07 '18 at 19:59
Thanks for advice. But I've already tried it and got the same error. — Damirov Eldar, Jun 07 '18 at 20:02
#ifdef _cplusplus extern "C" { #endif #include int get(); #ifdef _cplusplu } #endif — Damirov Eldar, Jun 07 '18 at 20:04
Did you add extern "C" declaration also in the .cpp file (or do you include the .hpp file from the .cpp file) ? — Martin R, Jun 07 '18 at 20:06
It should be `#ifdef __cplusplus`, with *two* underscore characters. — Martin R, Jun 07 '18 at 20:11

score 0 · Answer 1 · answered Jun 07 '18 at 19:57

0

There is not currently an interop between Swift and C++. You can easily do ObjC and C, but for C++ you're going to wrap your C++ code in ObjC.

answered Jun 07 '18 at 19:57

MultiColourPixel

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Hmm, but what about this: https://youtu.be/0x6JbiphNS4 – Damirov Eldar Jun 07 '18 at 20:03
He wasn't including the `.hpp` in the bridging header. He wrapped the C++ code in a C function and instead included a `.h` in the briding header and added the extern C in the wrapper. – MultiColourPixel Jun 07 '18 at 20:10
I've tried that also. Same error. – Damirov Eldar Jun 07 '18 at 20:11
Your code example doesn't indicate this. It still shows a `.hpp` being included in the bridging header. – MultiColourPixel Jun 07 '18 at 20:13
Sorry. Problem is already solved. Thanks for your assistance. – Damirov Eldar Jun 07 '18 at 20:14

Swift and C++ bridging in Xcode

1 Answers1