fix: also link libc++abi for RTTI — resolve missing __class_type_info vtable
Previous fix linked c++_static but not c++abi. Android NDK splits the static C++ runtime into two archives: libc++_static.a (STL) and libc++abi.a (RTTI/exceptions). Without c++abi, dlopen fails on _ZTVN10__cxxabiv117__class_type_infoE. Now using cpp_link_stdlib(None) to suppress cc crate auto-linking, then explicitly linking both c++_static and c++abi via cargo:rustc-link-lib. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Siavash Sameni
@@ -13,7 +13,7 @@ fn main() {
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cc::Build::new()
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.cpp(true)
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.std("c++17")
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.cpp_link_stdlib(Some("c++_static"))
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.cpp_link_stdlib(None)
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.file("cpp/oboe_bridge.cpp")
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.include("cpp")
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.include(oboe_path.join("include"))
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@@ -25,12 +25,19 @@ fn main() {
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cc::Build::new()
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.cpp(true)
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.std("c++17")
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.cpp_link_stdlib(Some("c++_static"))
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.cpp_link_stdlib(None)
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.file("cpp/oboe_stub.cpp")
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.include("cpp")
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.compile("oboe_bridge");
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}
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}
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// Android NDK splits the static C++ runtime into two archives:
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// libc++_static.a — STL (containers, strings, algorithms)
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// libc++abi.a — ABI (RTTI, exceptions, typeinfo vtables)
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// Both are required; cc crate's cpp_link_stdlib only handles the first.
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println!("cargo:rustc-link-lib=static=c++_static");
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println!("cargo:rustc-link-lib=static=c++abi");
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} else {
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// Non-Android: always use stub
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cc::Build::new()
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@@ -1,6 +1,6 @@
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# Issue 001: App crashes on launch — missing libc++_shared.so
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# Issue 001: App crashes on launch — C++ runtime not linked correctly
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## Status: Fix committed, needs rebuild
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## Status: Fix v2 committed, needs rebuild
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## Symptom
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@@ -13,77 +13,85 @@ or on any code path that first loads the native library.
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- Nothing Phone, arm64-v8a, Android 15
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- ADB device ID: `00142151B000973`
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## Logcat crash trace
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## Crash history
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### Attempt 1: `libc++_shared.so` not found
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```
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E AndroidRuntime: FATAL EXCEPTION: main
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E AndroidRuntime: Process: com.wzp.phone, PID: 6048
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E AndroidRuntime: java.lang.UnsatisfiedLinkError: dlopen failed: library "libc++_shared.so"
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not found: needed by /data/app/.../base.apk!/lib/arm64-v8a/libwzp_android.so
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in namespace clns-9
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E AndroidRuntime: at java.lang.Runtime.loadLibrary0(Runtime.java:1097)
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E AndroidRuntime: at java.lang.System.loadLibrary(System.java:1765)
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E AndroidRuntime: at com.wzp.engine.WzpEngine.<clinit>(WzpEngine.kt:115)
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E AndroidRuntime: at com.wzp.ui.call.CallViewModel.startCall(CallViewModel.kt:52)
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E AndroidRuntime: at com.wzp.ui.call.InCallScreenKt$InCallScreen$1$1$1.invoke(InCallScreen.kt:96)
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not found: needed by .../libwzp_android.so
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at com.wzp.engine.WzpEngine.<clinit>(WzpEngine.kt:115)
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```
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## Root cause
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**Cause**: `cc::Build` defaults to dynamic C++ linking. `libc++_shared.so` never
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packaged into APK.
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**Attempted fix**: `.cpp_link_stdlib(Some("c++_static"))` — link STL statically.
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### Attempt 2: missing `__class_type_info` vtable (RTTI)
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```
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E AndroidRuntime: java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol
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"_ZTVN10__cxxabiv117__class_type_infoE" referenced by .../libwzp_android.so
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at com.wzp.engine.WzpEngine.<clinit>(WzpEngine.kt:115)
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```
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**Cause**: Android NDK splits the static C++ runtime into two archives:
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- `libc++_static.a` — STL (containers, strings, algorithms)
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- `libc++abi.a` — ABI layer (RTTI typeinfo vtables, exception handling)
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The `cc` crate's `.cpp_link_stdlib(Some("c++_static"))` only emits
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`cargo:rustc-link-lib=static=c++_static`. It does NOT pull in `libc++abi.a`,
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so all RTTI symbols (`__class_type_info`, `__si_class_type_info`, etc.)
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are unresolved at dlopen time.
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## Root cause (full)
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`crates/wzp-android/build.rs` uses the `cc` crate to compile C++17 code
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(the Oboe audio bridge). On Android targets, `cc::Build` defaults to dynamically
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linking the C++ standard library (`libc++_shared.so`).
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(the Oboe audio bridge). Two things go wrong:
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This means `libwzp_android.so` has a runtime dependency on `libc++_shared.so`.
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However, the Gradle build (`cargoNdkBuild` task) only copies `libwzp_android.so`
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into `jniLibs/arm64-v8a/`. The C++ runtime is never copied alongside it, so the
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APK ships without `libc++_shared.so`.
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1. Dynamic linking by default → `libc++_shared.so` not in APK
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2. Even with `.cpp_link_stdlib("c++_static")`, the ABI half (`libc++abi.a`)
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is not linked, leaving RTTI symbols unresolved
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At runtime, `dlopen("libwzp_android.so")` fails because the linker can't find
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the missing shared library in the app's namespace.
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## Fix (v2)
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### Why this wasn't caught earlier
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The previous APK (pre-QUIC wiring) was 2.0MB release / 8.9MB debug. The Oboe
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C++ bridge was likely being compiled but the native library may not have been
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loaded on the code path that was tested, or the dependency was satisfied by a
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different linking configuration at the time.
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## Fix
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In `crates/wzp-android/build.rs`, add `.cpp_link_stdlib(Some("c++_static"))` to
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all `cc::Build` invocations targeting Android. This tells the `cc` crate to link
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`libc++_static.a` instead of `libc++_shared.so`, baking the C++ runtime directly
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into `libwzp_android.so`. No separate shared library needed at runtime.
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Suppress the `cc` crate's automatic C++ stdlib linking with `.cpp_link_stdlib(None)`,
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then explicitly link both static archives:
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```rust
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cc::Build::new()
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.cpp(true)
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.std("c++17")
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.cpp_link_stdlib(Some("c++_static")) // <-- this line
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.cpp_link_stdlib(None) // suppress cc crate's automatic linking
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.file("cpp/oboe_bridge.cpp")
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// ...
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.compile("oboe_bridge");
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// Manually link both halves of the Android NDK static C++ runtime
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println!("cargo:rustc-link-lib=static=c++_static");
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println!("cargo:rustc-link-lib=static=c++abi");
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```
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Applied to both the Oboe build path and the stub fallback path.
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This is placed once after the match block (applies to both Oboe and stub paths).
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### Trade-off
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Static linking increases `libwzp_android.so` size slightly (~200-400KB for
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libc++ static). This is acceptable — the alternative (bundling libc++_shared.so
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separately) adds complexity to the Gradle build and risks version mismatches if
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multiple native libraries each bundle their own shared copy.
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Static linking increases `libwzp_android.so` by ~300-500KB. Acceptable for
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avoiding shared library packaging complexity.
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## Rebuild steps
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```bash
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cd android && ./gradlew assembleRelease
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cd android && ./gradlew clean assembleRelease
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adb install -r app/build/outputs/apk/release/app-release.apk
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```
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Use `clean` to ensure the native library is fully relinked.
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## Verification
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After install, the app should:
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1. Open without crashing
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2. Load `libwzp_android.so` successfully (check logcat for absence of UnsatisfiedLinkError)
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2. Load `libwzp_android.so` successfully (no UnsatisfiedLinkError in logcat)
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3. Show the call UI with CALL button
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