I have a few simple C files that I would like to compile and use with cinterop, and I have a few questions 1. Is it possible to actually compile those C files as a part of my Gradle build? If so, what is the best way to go about it? 2. Assuming these C files compile to a static library and I include them in my Kotlin target, will they work on Android? Or do I need to write separate JNI bindings for Android, and then merge the interfaces into a cross-platform abstraction?

1. Yes, you create a cinterop setup as displayed here: https://kotlinlang.org/docs/native-app-with-c-and-libcurl.html#add-interoperability-to-the-build-process one thing should be noted, this will only work with native targets 2. They will work on android, but there is a lot of gotchas. You can't use the most heavy weight kotlin multiplatform libraries if you create a pure android native application (such as coroutines or atomicfu) or for obvious reasons, make use of the traditional android libraries. If you want to use jvm yes, your only choice here is to setup a separate JNI binding

@Joakim Forslund in that example

libcurl

is not compiled as a part of the build, but rather the system

libcurl

is linked from Kotlin

It sure is, they get compiled as a part of the cinterop setup

From the link:

You need to have the

curl

library binaries on your system to make the sample work.

Yes? And you just want to compile some files, the setup is still the same. Put the c files into the cinterop folder, but without the need to setup the obvious curl linking or include

Okay, put another way Inside of the

def

file,

curl/curl.h

is put into the

headers

field. If I have

hello.c

and

hello.h

, can I put a

.c

file into the

headers

field?

In that case your

def

file would contain

package = hello
headers = hello.h
headerFilter = hello.h
---

One way is to put your

.c

code under the

---

in the def file

I am able to get it working if the c code is below the

---

, but I am unable to get it to work any other way

I have several projects there the folder of the c files gets passed in as compilerOpts. Try placing the

.c

and the

.h

file in the same folder i.e

nativeInterop/cinterop/c

. Keep the same def file

actually, it worked if I just passed the

.c

file in the

headers

array

Sure, but interlinking issues might come from that

Sweet, I will fiddle with it. Further question, if I want to use

cinterop

on Android, I assume I need to use

androidNativeArm64

and not just

android

?

Yes

Because the functions are not

static

(they are from an external library), I either get “symbol multiply defined” if I include the

c

file or “symbol not found” if I do not