The way to name C code from Swift

The way to name C code from Swift

Interacting with C libraries from the Swift language is de facto superb, from this submit can be taught probably the most of C interoperability.


From Swift 4 there’s native assist for wrapping C libraries in Swift system module packages. This implies which you could eaily ship your personal system modules, you simply should discover ways to use the Swift Package deal Supervisor.😅

Bridging header inside Xcode

Let’s hearth up Xcode and begin a model new single view app iOS venture. Fill out the required fields, and naturally select the Swift language. Subsequent, add a brand new file and select the C file template.

After you enter the identify and examine the additionally create header file field, Xcode will ask you concerning the Goal-C bridging header file. Simply create it. The identify of this file is hard, as a result of it additionally helps different C household langages, like pure C or C++, Goal-C and plus-plus. 😉

Let’s create a public header for the C code (factorial.h):

#ifndef factorial_h
#outline factorial_h

#embody <stdio.h>

lengthy factorial(int n);

#endif /* factorial_h */

That is gona be the implementation of the tactic (factorial.c):

#embody "factorial.h"

lengthy factorial(int n) 

Contained in the bridging header, merely import the C header file:

#embody "factorial.h"

Someplace inside a Swift file you need to use the factorial methodology:

print("Hi there (factorial(5))!")

Compile and run. 🔨 It simply works. 🌟 Magic! 🌟

You are able to do the very same factor to make use of Goal-C lessons inside your Swift tasks. Apple has nice docs about this system, it’s best to learn that if you wish to know extra about combine and match.

Delivery C code with SPM

The true enjoyable begins once you begin utilizing the Swift Package deal Supervisor to construct C household based mostly sources. From Swift 3.0 you may construct C language targets with SPM. If you do not know methods to use the SPM instrument, it’s best to learn my complete tutorial concerning the Swift Package deal Supervisor first.

The one factor that you will must do this can be a correct listing construction (plus you may want the package deal description file), and the package deal supervisor will take care all the remaining. Right here is every thing what you could construct the factorial instance with SPM.

import PackageDescription

let package deal = Package deal(
    identify: "cfactorial",
    merchandise: [
        .library(name: "cfactorial", targets: ["cfactorial"]),
    targets: [
            name: "cfactorial",
            path: "./Sources/factorial"

The listing construction must be one thing like this.


You also needs to change the #embody "factorial.h" line contained in the factorial.c file to #embody "embody/factorial.h" as a result of we made a brand new embody listing. That is NOT needed, however when you do not put your umbrella header into the embody listing, you may want to offer a modulemap file, and supply the proper location of your header. In case you use the embody construction SPM will generate every thing for you.

With this system you may import your cfactorial module from another Swift package deal and name the factorial methodology, like we did via Xcode. You simply have so as to add this module as a dependency, oh by the best way you may even name this module from one other C venture made with SPM! 💥

.package deal(url: "", .department("grasp")),

Congratulations, you simply shipped your first C code with Swift Package deal Supervisor. Please try the instance repository, you may construct and run the venture by your self.

This setup additionally works with C, C++, Goal-C, Goal-C++ code.

Wrapping C [system] modules with SPM

If you wish to wrap a C [system] library and name it immediately from Swift you may crete a model new wrapper package deal with the assistance of the Swift Package deal Supervisor. To begin you need to use the swift package deal init --type system-module command, it will create a generic template venture.

These are particular packages based on Apple, you simply should ship your personal modulemap and a header file to show the wanted APIs, however first – clearly – you may want the same old package deal definition file:

import PackageDescription

let package deal = Package deal(
    identify: "ccurl",
    suppliers: [

Contained in the Package deal.swift file you may set the suppliers for the library (like brew on macOS or aptitude for ubuntu / debian and the others). Right here is an effective recommendation for you: sudo apt-get set up pkg-config beneath linux to make issues work, as a result of the system will seek for package deal header recordsdata with the assistance of the pkgConfig property. For instance if you wish to use libxml2 and pkg-config is just not put in, you will not be capable of compile / use your system module.

Subsequent you may want a module.modulemap file, which is fairly easy.

module ccurl [system] {
    header "shim.h"
    hyperlink "curl"
    export *

Concerning the hyperlink property see Xcode launch notes seek for “auto-linking”

Lastly add an additional shim.h header file to import all of the required APIs. Normally I do not prefer to import immediately the required header recordsdata from the modulemap file that is why I’m utilizing this “shim.h” – identify it such as you need – you may see in a second why am I prefering this methodology, however here’s a primary one.


#import <curl/curl.h>;


Let’s discuss why I like importing the shim file. If in case you have platform variations you need to use a neat trick with the assistance of utilizing macros, for instance you may import header recordsdata from completely different areas when you examine for the __APPLE__ platform macro.


#ifdef __APPLE__
    #embody "/usr/native/embody/instance.h"
    #embody "/usr/embody/instance.h"


Cool, huh? 🍎 + 🔨 = ❤️


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