Hi guys, I have been trying to build static library for Android to be used in a Go binding go-sdl2 to produce a shared library that can be loaded by Android but haven’t been successful. I have almost no Android experience so I used the guide here as reference to create the following script that builds the SDL2 static library.
# build-android.sh inside SDL2-2.26.1 directory
mkdir build-android_arm && cd build-android_arm
export TARGET=armv7a-linux-androideabi
export NDK=/opt/android-ndk-r25b
export TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/linux-x86_64
export API=21
export AR=$TOOLCHAIN/bin/llvm-ar
export CC=$TOOLCHAIN/bin/$TARGET$API-clang
export AS=$CC
export CXX=$TOOLCHAIN/bin/$TARGET$API-clang++
export LD=$TOOLCHAIN/bin/ld
export RANLIB=$TOOLCHAIN/bin/llvm-ranlib
export STRIP=$TOOLCHAIN/bin/llvm-strip
export LDFLAGS="-lOpenSLES"
../configure --host $TARGET
make -j`nproc`
However, it ran into an error below which I suppose is related to src/hidapi/android/hid.cpp not being compiled? It seems to be included in the SDL2-2.26.1/Android.mk file but I’m not sure how to make use of the make file.
...
CC build/SDL_virtualjoystick.lo
LTLINK build/libSDL2.la
ld: error: undefined symbol: PLATFORM_hid_init
>>> referenced by SDL_hidapi.c:1140 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1140)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_init)
>>> referenced by SDL_hidapi.c:1140 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1140)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_device_change_count)
>>> referenced by SDL_hidapi.c:1140 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1140)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_enumerate)
>>> referenced 2 more times
ld: error: undefined symbol: PLATFORM_hid_exit
>>> referenced by SDL_hidapi.c:1172 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1172)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_exit)
ld: error: undefined symbol: PLATFORM_hid_enumerate
>>> referenced by SDL_hidapi.c:1283 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1283)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_enumerate)
ld: error: undefined symbol: PLATFORM_hid_free_enumeration
>>> referenced by SDL_hidapi.c:1338 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1338)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_enumerate)
>>> referenced by SDL_hidapi.c:1322 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1322)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_enumerate)
ld: error: undefined symbol: PLATFORM_hid_open
>>> referenced by SDL_hidapi.c:1378 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1378)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_open)
ld: error: undefined symbol: PLATFORM_hid_open_path
>>> referenced by SDL_hidapi.c:1412 (/opt/tmp/SDL2-2.26.1/src/hidapi/SDL_hidapi.c:1412)
>>> build/.libs/SDL_hidapi.o:(SDL_hid_open_path)
ld: error: undefined symbol: PLATFORM_hid_write
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_read_timeout
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_read
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_set_nonblocking
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_send_feature_report
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_get_feature_report
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_close
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_get_manufacturer_string
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_get_product_string
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_get_serial_number_string
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_get_indexed_string
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
ld: error: undefined symbol: PLATFORM_hid_error
>>> referenced by SDL_hidapi.c
>>> build/.libs/SDL_hidapi.o:(PLATFORM_Backend)
clang-14: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [Makefile:161: build/libSDL2.la] Error
The static libraries produced (libSDL2.a and libSDL2main.a) will be used in an example Go code when running builds in Go to produce shared library libexample.so that will be loaded by Android code like this:
package com.example.android;
import org.libsdl.app.SDLActivity;
public class MyGame extends SDLActivity {
@Override
protected String[] getLibraries() {
return new String[] {
"example"
};
}
@Override
protected String getMainFunction() {
return "SDL_main";
}
}
I would be very grateful if there’s someone who could point me in the right direction as I have been trying for hours. I apologize if there’s some missing information but I can share more if needed!