From 3d6789cb7065b3e10a0ed6ed42d2a9943e26ab58 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adam=20Cig=C3=A1nek?= <adam.ciganek@proton.me>
Date: Tue, 23 Jan 2024 16:48:42 +0100
Subject: [PATCH] bindings/kotlin: Fix native lib not found error in example
 app on x86_64

Closes #160
---
 bindings/kotlin/.gitignore       |  1 +
 bindings/kotlin/lib/build.gradle | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/bindings/kotlin/.gitignore b/bindings/kotlin/.gitignore
index 872d8e935..075339fa1 100644
--- a/bindings/kotlin/.gitignore
+++ b/bindings/kotlin/.gitignore
@@ -4,4 +4,5 @@
 # Ignore Gradle build output directory
 build
 
+local.properties
 *.hprof
diff --git a/bindings/kotlin/lib/build.gradle b/bindings/kotlin/lib/build.gradle
index 463b007d5..8213c87a6 100644
--- a/bindings/kotlin/lib/build.gradle
+++ b/bindings/kotlin/lib/build.gradle
@@ -7,6 +7,7 @@ plugins {
 
 android {
     compileSdkVersion 33
+
     ndkVersion '25.2.9519653'
 
     namespace 'org.equalitie.ouisync'
@@ -64,10 +65,29 @@ dependencies {
 cargo {
     module = "$rootDir/../.."
     libname = 'ouisync_ffi'
+
+    // Targets can be overriden with "rust.targets" in local.properties.
+    // Example: "rust.targets=arm64,x86_64".
+    // More info: https://github.com/mozilla/rust-android-gradle.
     targets = ['arm', 'arm64', /* 'x86', */ 'x86_64']
+
     profile = 'release'
 
     extraCargoBuildArguments = ['--package', 'ouisync-ffi']
+
+    // HACK: Recent NDK (since r23) no longer links `libgcc`, which breaks some libraries since
+    // they depended on the symbols from `libclang_rt.builtins-x86_64-android`
+    // (e.g. `__extenddftf2`, ...). To work around it, we link the library explicitly by setting
+    // it through the RUSTFLAGS env variable.
+    // More info: https://github.com/bbqsrc/cargo-ndk/issues/94.
+    exec { spec, toolchain ->
+        if (toolchain.target == 'x86_64-linux-android') {
+            def clangVersion = '14.0.7'
+            def libDir = "${android.sdkDirectory}/ndk/${android.ndkVersion}/toolchains/llvm/prebuilt/linux-x86_64/lib64/clang/${clangVersion}/lib/linux"
+
+            spec.environment('RUSTFLAGS', "-L${libDir} -lstatic=clang_rt.builtins-x86_64-android")
+        }
+    }
 }
 
 tasks.register('generateBindings', Exec) {