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Troubleshooting

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Troubleshooting

Update Packages

Several different issues are related to outdated libraries (e.g. https://github.com/fzyzcjy/flutter_rust_bridge/discussions/2953). The first suggested step is to update them. For example, to update Rust, from the root of your project:

cd rust && cargo update && cd ..

Linker complains undefined symbols

e.g. ld: Undefined symbols: std::__1::basic_string ...

Please change the following line in iOS/macos podspec file:

'OTHER_LDFLAGS' => '-force_load ${BUILT_PRODUCTS_DIR}/librust_lib.a',

To something like:

'OTHER_LDFLAGS' => '-force_load ${BUILT_PRODUCTS_DIR}/librust_lib.a -lc++',

Or other libraries that you need (e.g. -framework SystemConfiguration, -framework AudioToolbox, etc).

Please refer to these issues for more details: cargokit#52, bridge#1610.

Another example, which solves the error when using cpal, can be found in #1835.

Issues with glibc (e.g. version GLIBC_2.33 not found)

As is discussed in this issue and this issue:

This is a https://github.com/canonical/flutter-snap/issues/109 with Flutter Snap not being able to do LTO builds. Just install the Flutter regular way (without snap) and it should work.

Issue with store_dart_post_cobject

If calling rust function gives the error below, please consider running cargo build again. This can happen when the generated rs file is not included when building is being done.

sh
[ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Invalid argument(s): Failed to lookup symbol 'store_dart_post_cobject': target/debug/libadder.so: undefined symbol: store_dart_post_cobject

Error running cargo ndk: ld: error: unable to find library -lgcc

Downgrade Android NDK to version 22. This is an ongoing issue with cargo-ndk, a library unrelated to flutter_rust_bridge but solely used to build the examples, when using Android NDK version 23. (See #149)

Fail to run flutter_rust_bridge_codegen on MacOS, "Please supply one or more path/to/llvm..."

If you are running macOS, you will need to specify a path to your llvm:

shell
flutter_rust_bridge_codegen --rust-input path/to/your/api.rs --dart-output path/to/file/being/bridge_generated.dart --llvm-path /usr/local/homebrew/opt/llvm/

You can install llvm using brew install llvm and it will be installed at /usr/local/homebrew/opt/llvm/ by default.

Freezed file is sometimes not generated when it should be

If your .freezed.dart or .g.dart seems outdated, ensure you have run the build_runner.

Related: https://github.com/fzyzcjy/flutter_rust_bridge/issues/330

Can't create typedef from non-function type.

Ensure min sdk version of Flutter pubspec.yaml is at least 2.17.0 to let ffigen happy.

https://github.com/fzyzcjy/flutter_rust_bridge/issues/334

Imported from both bridge_definitions.dart and bridge_generated.io.dart

If you use a Rust type with Kind in it's name it may conflict with some generated types which can cause a duplicate import error. The workaround is to avoid using Kind as a suffix for a type name in Rust. See issue #757 for more details.

Error on iOS TestFlight only (store_dart_post_cobject)

You may have an iOS app that works fine in Debug and Release modes locally but when deployed to TestFlight an error occurs trying to locate the store_dart_post_cobject - this is because the nested XCode project for the native bindings maybe be stripping symbols from the linked product.

Select the scheme (eg: Product > Scheme > native-staticlib) and go to Build Settings then under the Deployment section change Strip Linked Product to No; you may also need to change Strip Style to Debugging Symbols.

Generated code is so long

Indeed all generated code are necessary (if you find something that can be simplified, file an issue). Moreover, other code generation tools also generate long code - for example, when using Google protobuf, a very popular serialization library, I see >10k lines of Java code generated for a quite simple source proto file.

Why need Dart 2.17.0

Dart SDK >=2.15.0 is supported by this library, but by the latest version of the ffigen tool requires >=2.17.0. Therefore, write sdk: ">=2.17.0 <3.0.0" in the environment section of pubspec.yaml. If you do not want that, consider installing a older version of the ffigen tool.

Why doesn't flutter_rust_bridge_serve work on Firefox?

This is a known issue stemming from Firefox's stricter rules regarding cross-origin requests. Use Chromium for testing, and check out this guide on enabling crossOriginIsolated for your production servers.

"Could not resolve symbol __cxa_pure_virtual", or libc++_shared issues.

At the time of writing this, linking with libc++_static or not linking at all may lead to symbol resolution errors when launching the flutter application, after loading your dynamic library. Adding a fix is quite easy, create a build.rs script in the root of your Rust code:

build.rs

rust
fn main() {
    #[cfg(target_os = "android")]
    println!("cargo:rustc-link-lib=c++_shared");
}

Then, in each jniLibs architecture directory, put the corresponding libc++_shared.so from the Android NDK. libc++_shared.so is typically located in $ANDROID_NDK/toolchains/llvm/prebuilt/. You will have to search for it, as it's different for each operating system.

  • arm-linux-androideabi -> armeabi-v7a
  • aarch64-linux-android -> arm64-v8a
  • i686-linux-android -> x86
  • x86_64-linux-android -> x86_64

Issues on Web?

Check out Limitations on WASM for some common problems and solutions to adapt existing code to WASM.

Cargokit fails with the SEVERE: error[E0463]: can't find crate for "core" error when building for macos target

Try to uninstall the rust toolchain and install it again from the scratch:

  1. rustup self uninstall
  2. curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
  3. flutter clean && flutter pub get && flutter run -d macos

Check the related issue on GitHub for the context.

Warning: unexpected cfg condition name: frb_expand

Please refer to #2425 for more details.

Shortly speaking, it seems flutter_rust_bridge cannot do much, just like the same scenario in cargo-fuzz. Instead, users may need to add the section below in Cargo.toml:

[lints.rust]
unexpected_cfgs = { level = "warn", check-cfg = ['cfg(frb_expand)'] }

flutter_rust_bridge_codegen is running forever

A debug approach is to use RUST_LOG=debug flutter_rust_bridge_codegen your_args to get more logs. For example, suppose it is stuck at executing fvm flutter pub get ..., then maybe try to execute that command directly in the shell and see whether it also get stuck.

Failed to load dynamic library 'librust_lib_my_app.so': dlopen failed: library "librust_lib_my_app.so"

flutter_rust_bridge is compatible with both old and new Flutter. If you see error like Flutter plugin not found, CargoKit plugin will not be applied. or dlopen failed: library "librust_lib_my_app.so" not found in flutter run --verbose, then it is probably because the Cargokit (rust_builder/cargokit) version in your project () does not match the Flutter version and need the following changes:

Cargokit compatibility with Flutter

Related issue: https://github.com/fzyzcjy/flutter_rust_bridge/issues/2802

Other problems?

Don't hesitate to open an issue! I usually reply within minutes or hours (except when sleeping, of course).