Calling Swift from C++

foo.swift

@_cdecl("foo")
public func foo(x: Int) -> Int {
    x * x
}

The @_cdecl will disable name mangling and enforces cdecl-calling convention.

main.cpp

#include <iostream>

extern "C" int foo(int);

int main()
{
    int x = foo(8);
    std::cout << x << std::endl;
}

Build commands

swiftc -emit-library foo.swift
clang++ -o main main.cpp libfoo.dylib

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Links:

• GitHub Gist: Swift Meets C/C++