Hello, I have an issue with cinterop trying to com...

# kotlin-native

[Miguel Santos]

Hello, I have an issue with cinterop trying to compile in macos for a linux (X, arm) target.
It fails on compileNativeMainKotlinMetadata :

e: file:///Users/myuser/Projects/demo/src/nativeMain/Main.kt:12:8 Unresolved reference: libpq

In summary:
Linux machine (x64):
• linuxX64 ✅
• linuxArm64 ❌ (I think it's supposed to work)
Macos machine (arm64):
• macosX64 ✅
• macosArm64 ✅
• linuxX64 ❌
• linuxArm64 ❌
Not sure why linuxX64 works on Linux machine but not Macos. Appreciate if someone could provide help or even a way to debug this issue (not sure where to start).

[Miguel Santos]

Currently defining the cinterop like this:

macosArm64 {
        val main by compilations.getting
        val libpq by main.cinterops.creating {
            defFile(project.file("src/nativeInterop/cinterop/libpq.def"))
        }
    }

[Landry Norris]

Did you copy headers into your project, or are you using system headers? If you're using system headers, they may not be in the same place or compatible on other compilation hosts.

[Miguel Santos]

Not too sure what the difference between those two options is..
This is my current .def file:

headers = libpq-fe.h
headerFilter = *
package = libpq

compilerOpts = -I/opt/homebrew/opt/libpq/include -I/usr/local/opt/libpq/include
linkerOpts = -L/opt/homebrew/opt/libpq/lib -L/usr/local/opt/libpq/lib -lpq

[Miguel Santos]

Ok, so made some progress.
This flag seems to fix compileNativeMainKotlinMetadata for all targets, but I don't fully understand what it does:

kotlin.mpp.enableCInteropCommonization=true

However, it now fails for linkDebugTestLinuxX64 :

ld.lld: error: undefined symbol: PQsetdbLogin
>>> referenced by out
>>>               /private/var/folders/dg/z7k2610n0vd0qgqzc7v17pxr0000gn/T/konan_temp16050745230498861662/test.kexe.o:(libpq_PQsetdbLogin_wrapper5)
>>> did you mean: _PQsetdbLogin
>>> defined in: /usr/local/opt/libpq/lib/libpq.a

So: macosArm64 ✅ , macosX64 ✅ , linuxArm64 ✅, linuxX64 ❌.

For reference, I also had to stop using the same libpq.def for all targets, since macosX64 was failing on linkDebugTestMacosX64 because it was finding the arm64 version of libpq first:

ld: symbol(s) not found for architecture x86_64

So now arm64 .def points to arm64 libpq installation, and x64 .def points to x64 libpq installation.

[Miguel Santos]

Turns out libpq homebrew version for macosX64 isn't compatible with linuxX64, even though the arm64 ones are. Compiling successfully for all 4 targets now.
Problem is, having a different .def file (i.e., link paths) for each target isn't suitable for this project, because it is a library.

So I still have to find a way to have the same .def for all targets, and be able to build this in my machine and in a pipeline.

[Landry Norris]

I believe you can use <setting>.<target> to specify per target. For example:

linkerOpts.linuxX64 = ...
linkerOpts.macosArm64 = ...
...

[Landry Norris]

I usually create a folder in my project called prebuilts, with per-target headers and binaries. This allows the project to be built on other targets without worrying about headers being compatible.

[Miguel Santos]

If you have an example with prebuilts I'd appreciate it.
Otherwise, <setting>.<target> looks good. Cheers Landry 👍

[Landry Norris]

I don't think I have any public examples of this. I used it on an internal project at a previous job. The basic gist is to create prebuilts/linuxX64/headers or prebuilts/macosX64/binaries, etc (you can choose whether targets or header/binary are the first differentiator). Copy the binary and header from each platform into the proper build folder. The defs should direct to these folders.

[Miguel Santos]

Awesome, thanks for the tips 🙏