latest gomobile arm64-only?

[andrey mirtchovski]

I'm having issues with the latest gomobile + reverse java bindings. I
have a piece of code that linked with a C library via CGO. Previously
(around 6 months ago) everything appeared file: cross compile library
with NDK toolchain (gcc), link against go code with cgo, run "gomobile
bind -target=android" and everything worked.

now it appears gomobile has switched to targeting arm64 with clang. I
tried compiling my code against 32-bit gcc, 32-bit clang, and 64-bit
clang. even though i can create a successful 32-bit arm binary with
the standard Go tools, I am unable to create one with gomobile. here's
an example of the 32-bit library I'm using (i've also compiled it
static):

/opt/arm-linux-androideabi/sysroot/usr/lib/mylibrary.so: ELF 32-bit
LSB shared object, ARM, version 1 (SYSV), dynamically linked (uses
shared libs), not stripped

gradle build however invokes gomobile bind thusly (major parts of the
classpaths stripped):


--------8<----------------
/.../gomobile bind -i -classpath
/.../android/android/build/intermediates/exploded-aar/com.android.support/appcompat-v7/24.2.1/jars/classes.jar:[...]:/.../android/android/build/intermediates/classes/debug
-o /var/folders/sp/06p28g2d0vs7gd2vhf26wl9m0000gn/T/gobind-2223404674934856774.aar
-target android -bootclasspath
/.../sdk/platforms/android-24/android.jar -x my/project

gomobile then issues this command and receives the following error:

/Users/aam/pkg/gomobile/android-ndk-r12b/arm64/bin/aarch64-linux-android-clang
-I . -fPIC -pthread -fno-caret-diagnostics -Qunused-arguments
-fmessage-length=0 -fdebug-prefix-map=$WORK=/tmp/go-build
-gno-record-gcc-switches -o $WORK/my/project/_obj/_cgo_.o ...-target
aarch64-none-linux-android --sysroot
/.../pkg/gomobile/android-ndk-r12b/arm64/sysroot
/opt/arm-linux-androideabi/sysroot/usr/lib/mylibrary.a -lm -lz -pie

# my/project

/opt/arm-linux-androideabi/sysroot/usr/lib/mylibrary.a: error adding
symbols: File in wrong format

clang: error: linker command failed with exit code 1 (use -v to see invocation)
--------8<----------------

again, this works when using GOOS=arm GOARCH=android CGO_ENABLED=1 go
build... also, the reverse example works fine with this setup, but
that doesn't attempt any cgo tomfoolery.

TL;DR: i'm unable to figure out a way to force 32-bit gomobile
compilation, especially while staring from outside the "gradle build"
wall.

[Elias Naur]

The gradle plugin supports the GOARCH settings which contains a list of the architectures you want to include. Use it in your gobind {...} section of your build.gradle, along with your "pkg" setting:

apply plugin: "org.golang.mobile.bind"

gobind {
	pkg = "...golang.org/x/mobile/example/bind/hello"

	GOARCH = "arm"
}

 - elias

[andrey mirtchovski]

Thanks, this works perfectly!

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