NDK 23 beta: Build fails with unable to find library -lgcc

[zskamljic]

I'm trying to build a new project, however when running the command cargo ndk -t aarch64-linux-android -o ./jniLibs build --release, but I end up with an error;

error: linking with `/home/<user>/Android/Sdk/ndk/23.0.7421159/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android21-clang` failed: exit status: 1
  |
  = note: ld: error: unable to find library -lgcc
          clang-12: error: linker command failed with exit code 1 (use -v to see invocation)

[bbqsrc]

Does it work if you use ndk 22.x or lower?

[zskamljic]

Yes, it seems that way the .so file is created

[bbqsrc]

So, NDK 23 removes libgcc entirely. Rust relies on this for providing missing builtins on Android.

rust-lang/rust#85806 should fix it.

[bbqsrc]

This seems to still only work with nightly. To use aarch64 builds as an example, this will work:

cargo +nightly ndk -t arm64-v8a build -Zbuild-std

The problem seems to be the Rust CI builds for Android still use an older NDK or something similar that causes it to require libgcc. If you build your own std, no problem.

[bbqsrc]

@tux3 this is a separate issue, please create one and report this there 😄

[acrrd]

Do you think that porting this workaround will be suitable for cargo ndk?
https://github.com/rust-windowing/android-ndk-rs/blob/f24606cc840af2f97f0daebe1e2e7cd3aca52287/cargo-apk/src/apk.rs#L184

[bbqsrc]

If somebody wishes to do so.

[Fernthedev]

I'd like to mention that the workaround named above (building with std) does not work in my situation. I am using NDK R24 if that requires mentioning
I still get ld: error: unable to find library -lgcc using this command invocation:

rustup target install aarch64-linux-android
rustup component add rust-src --toolchain nightly --target aarch64-linux-android
cargo +nightly ndk -t arm64-v8a -o target/release build -Zbuild-std --verbose --release

If anyone would like to test this very specific scenario, the project is over here and shouldn't require extensive setup configurations.

Note:

• I have not tested with other NDK versions
• I have not tested other rust projects

Am I missing something? Feel free to call me out on it

Update:
Tested NDK R23c and still does not work

[Qinruiy]

I'd like to mention that the workaround named above (building with std) does not work in my situation. I am using NDK R24 if that requires mentioning I still get ld: error: unable to find library -lgcc using this command invocation:

rustup target install aarch64-linux-android
rustup component add rust-src --toolchain nightly --target aarch64-linux-android
cargo +nightly ndk -t arm64-v8a -o target/release build -Zbuild-std --verbose --release

If anyone would like to test this very specific scenario, the project is over here and shouldn't require extensive setup configurations.

Note:

• I have not tested with other NDK versions
• I have not tested other rust projects

Am I missing something? Feel free to call me out on it

Update: Tested NDK R23c and still does not work

rust-lang/rust#85806 (comment)

create 4 text files named libgcc.a in the same folders with this contents
it works on ndk 24.0.8215888

[rib]

Do you think that porting this workaround will be suitable for cargo ndk? https://github.com/rust-windowing/android-ndk-rs/blob/f24606cc840af2f97f0daebe1e2e7cd3aca52287/cargo-apk/src/apk.rs#L184

For reference the PR #67 I recently opened effectively supports this same workaround.