Swift の String を UnsafeMutablePointer<UnsafeMutablePointer<Int8>?>! にする

sample.swift

import Foundation

let options = ["-m" : 2, "-n" : 3]

var args : [String] = []
for (option_name, value) in options {
    args.append(contentsOf: [option_name, value])
}
var cargs: [UnsafeMutablePointer<Int8>?] = args.map { strdup($0) }
initialize(Int32(args.count), &cargs)
for ptr in cargs { free(ptr) }

sample.c

void initialize(int argc, char **argv) {
    // いろいろ
}

See: https://developer.apple.com/documentation/swift/unsafemutablepointer

C の UnsafeMutablePointer<Int8>? を Swift の String にする

sample.swift

let foo = get_foo()
let result = String(cString: foo!) // TODO: nil 安全にすべき
print(result)

sample.c

char* get_foo() {
    // return うんたら
}