RFR: 8370659: [mobile] enable static-libs-image for Android

[Johan Vos]

On Sun, 26 Oct 2025 16:10:09 GMT, Johan Vos <jvos at openjdk.org> wrote:

> This PR adds the changes required to compile libjvm.a and the classlibs using the latest upstream code.
> 
> Some notes:
> 
> To configure/make, the following configuration is recommended:
> 
> bash ./configure \
> --disable-warnings-as-errors \
> --openjdk-target=aarch64-linux-android \
> --with-boot-jdk=/opt/jdk-25 \
> --with-toolchain-path=/opt/android-ndk-r29/toolchains/llvm/prebuilt/linux-x86_64/bin \
> --with-sysroot=/opt/android-ndk-r29/toolchains/llvm/prebuilt/linux-x86_64/sysroot \
> --with-toolchain-type=clang
> 
> 
> After configuring the build, run
> `make static-libs-image`
> 
> Note that this requires Android NDK 29, which can be downloaded from https://developer.android.com/ndk/downloads 
> I only tested this using Linux. Mac/Windows builds may or may not work.
> 
> In `make/autoconf/flags-cflags.m4`, the minimum android version is set to 32 (`-target aarch64-linux-android32`). The reason for this is that this version comes with a version of bionic that supports thr_current. This is not strictly needed, but lower versions would require more bionic-specific patches.
> 
> I use `#ifdef  __BIONIC__ `and similar in most places where we do "Android" specific checks. The reason for this is that those checks mainly refer to support that is (or isn't) available in Bionic. As such, it is better to compare e.g. bionic with musl and libc unless we are specifically using Android API's
> 
> I can provide a sample with a Makefile that validates the build on a real phone, but I think that is not in scope of this PR.

I added a sample that describes how to use the resulting OpenJDK to create and run a HelloJava application directly on a phone: https://github.com/openjdk-mobile/android-tools/tree/main/samples/adbhelloworld

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PR Comment: https://git.openjdk.org/mobile/pull/40#issuecomment-3448746308