Create C-bindings article

src/content/resources/kotlin/native/creating-c-bindings.md

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+---
+authors:
+  - "supergrecko#3434"
+created_at: "2019/08/23"
+title: "Creating C bindings with Kotlin/Native"
+external_resources:
+  - "https://kotlinlang.org/docs/reference/native/c_interop.html"
+  - "https://github.com/JetBrains/kotlin-native/releases"
+---
+
+## Interoperability with C
+
+Kotlin/Native supports interoperability with the C programming language. This article will show you how to create bindings between C and Kotlin/Native.
+
+### Setup
+
+This guide assumes you already have the Kotlin compiler and the GCC C compiler installed on your computer.
+
+If you do not have the Kotlin compiler installed on your computer you can download it from the GitHub releases linked above.
+
+### Creating our C library
+
+We will be creating a very simple library to demonstrate linking.
+
+This is our `App.h` file
+```c
+#ifndef APP_H
+#define APP_H
+
+void run();      
+
+#endif 
+```
+
+And this is our `App.c` file
+
+```c
+#include <stdio.h>
+#include "App.h"
+
+void run() {
+    printf("Hello, from C");
+}     
+```
+
+### Compiling our C library
+
+First of all we will need to compile our C sources.
+
+```bash
+gcc -c "-I$(pwd)" App.c -o App.o
+```                       
+
+The `"-I$(pwd)"` flag translates to the gcc -I flag with our current working directory as its parameter. You can also type out the full path if you want to.
+
+We now have our compiled C code in `App.o`. Now we have to turn the compiled output into a static library.
+
+We'll save our compiled static library in a file named `App.a`
+
+```bash
+ar rcs App.a App.o
+```               
+
+### Compiling our bindings
+
+Now we need to create a `App.def` file for the Kotlin cinterop tool
+    
+The minimal requirements for a `.def` file is some headers. We will include our header file here.
+    
+```def
+headers = App.h
+```
+
+We will run the `cinterop` command to generate the Kotlin bindings for our C library.
+
+```bash
+cinterop -def App.def -compilerOpts "-I$(pwd)" -o App.klib
+```
+
+We're now ready to create a Kotlin file to interact with our C library so let's do that. Let's name this file `App.kt`
+
+```kotlin
+import App.run
+
+fun main() {
+    println("Hello, from Kotlin/Native") 
+    run()
+}
+```
+
+We'll print out a hello from Kotlin, and then the hello from C.
+
+### Executing our Kotlin
+
+There is only one more step before we can run our Kotlin application, we need to compile our Kotlin, so let's do that.
+
+Using the konanc compiler we will bundle our C library with our Kotlin file.
+
+```bash
+konanc -l App.klib App.kt -linker-options App.a -o App.kexe
+```
+
+We can now run our executable so let's do that.
+
+```bash
+./App.kexe
+```       
+
+This should be the program output:
+```text
+Hello, from Kotlin/Native
+Hello, from C     
+```