Build SDL2 Demo using CMake for Android

Laz-Roc · November 12, 2013, 1:52am

Hey, I need another help with SDL2 + CMake for Android. I almost got my cross-build demo working - Linux, Mac, iOS, and Windows are running, but Android is still somewhat draconian.

What works: A little test program based on the android-project within the SDL2 sources.
What I try: Build this same demo with CMake to simplify cross-platform development,

… but first I need to build SDL2 with CMake:

For that project I rely on the android-cmake (http://code.google.com/p/android-cmake/) toolchain, and its very outdated boost tutorial. Anyway, it works somehow and I only have to figure out the build process. Now, I try to apply it for my project, creating the CMakeLists.txt file based on the boost tutorial and modify it based on the Android.mk file inside the SDL package. This is my CMakeLists.txt (http://pastebin.com/P4iWfPHs) so far:

Code:
cmake_minimum_required(VERSION 2.8)
project(SDL2)

set(SDL_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/SDL)
include_directories(${SDL_ROOT}/include)

file (GLOB SOURCES
${SDL_ROOT}/src/.c
# …
${SDL_ROOT}/src/render//.c
# …
${SDL_ROOT}/src/test/.c
)

add_library (SDL2 ${SOURCES})
target_link_libraries (SDL2 dl GLESv1_CM GLESv2 log android)

Looks to simple to work out of the box, and unfortunately it is true. The generation of the makefiles works, but the actual make process fails:

Code:
Scanning dependencies of target SDL2
[ 0%] Building C object CMakeFiles/SDL2.dir/SDL/src/SDL_hints.c.o
…
[ 35%] Building C object CMakeFiles/SDL2.dir/SDL/src/render/opengles/SDL_render_gles.c.o
In file included from /AndroidCMake/SDL/src/render/opengles/SDL_render_gles.c:203:0:
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h: In function ‘GLES_LoadFunctions’:
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:3:1: error: ‘glBlendFuncSeparateOES’ undeclared (first use in this function)
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:3:1: note: each undeclared identifier is reported only once for each function it appears in
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:11:1: error: ‘glDrawTexfOES’ undeclared (first use in this function)
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:15:1: error: ‘glGenFramebuffersOES’ undeclared (first use in this function)
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:33:1: error: ‘glBindFramebufferOES’ undeclared (first use in this function)
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:34:1: error: ‘glFramebufferTexture2DOES’ undeclared (first use in this function)
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:35:1: error: ‘glCheckFramebufferStatusOES’ undeclared (first use in this function)
/AndroidCMake/SDL/src/render/opengles/SDL_glesfuncs.h:40:1: error: ‘glDeleteFramebuffersOES’ undeclared (first use in this function)
make[2]: *** [CMakeFiles/SDL2.dir/SDL/src/render/opengles/SDL_render_gles.c.o] Error 1
make[1]: *** [CMakeFiles/SDL2.dir/all] Error 2
make: *** [all] Error 2

There’s a similar thread (http://forums.libsdl.org/viewtopic.php?t=9696) on in this forum, but I don’t get it. Btw. there’s a confusing thread in the thread.

Okay, that’s where I stuck. Any help is welcome to get it done, thanks.
Michael

Eric_Wing · November 12, 2013, 3:37am

Hi Michael,
This won’t directly solve your problem, but will give you more
information on how to use Android-CMake, and more generally, the
Android NDK build chain, in non-trivial Android projects with
dependencies.

I have a sample repository for an Android Hello World program that
uses ALmixer. ALmixer uses CMake to build (consider it your SDL
proxy). I use my own fork of Android-CMake which contains fixes to use
the latest NDKs, as well as handle multiple architectures (arm, armv7,
x86).

(Note that this example compiles ALmixer without SDL dependencies and
instead uses a new experimental native Android OpenSL ES decoder
backend my team and I have been working on so it won’t directly show
you how to deal with SDL.)

Additionally, OpenAL-Soft is a dependency that ALmixer depends on,
though this uses its own supplied Makefile system.

Once these components are built as dynamic libraries, the final Hello
World app build process relies on the official NDK module system to
find ALmixer and OpenAL and build appropriately.

All of this is strung together by some Perl scripts.

The README.txt contains a lot of information on how to setup things.
Android NDK development is really painful so take your time on this.
Don’t expect to be able to grasp everything in 10 minutes.

The repository can be found at:

Hope this helps,
EricOn 11/11/13, Laz-Roc wrote:

Hey, I need another help with SDL2 + CMake for Android. I almost got my
cross-build demo working - Linux, Mac, iOS, and Windows are running, but
Android is still somewhat draconian.

Okay, that’s where I stuck. Any help is welcome to get it done, thanks.
Michael

–
Beginning iPhone Games Development
http://playcontrol.net/iphonegamebook/

Laz-Roc · November 13, 2013, 1:30am

Thanks Eric. Just got the sources and give it all a try the next days. And you are absolutely right, NDK is a pain. I really thought it couldn’t be more worse than iOS, but I may be wrong. I’ll report then.

Laz-Roc · November 23, 2013, 6:58pm

Have been away for awhile, but I’m back to tackle that Android + CMake problem again.

Well, I think I’ve been successful building a static SDL2 library with CMake, but wasn’t able to build an app so I don’t know if it’s working. Vice versa, I couldn’t build a static library with the provided SDL2 README, but a demo with a shared library.

I’d like to build a shared library, anyway. So I slightly modified my CMakeLists.txt (http://pastebin.com/6mHJYcDf) to building a shared library by adding the SHARED tag.

Again, it creates the makefiles, and builds the object files. But I don’t know how to solve the undefined reference error. Here are some of the errors (I stripped similar errors; here is the full error message (http://pastebin.com/1mn2Utsd)):

Linking C shared library …/libs/armeabi-v7a/libSDL2.so
/Android/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld: CMakeFiles/SDL2.dir/SDL/src/SDL_assert.c.o: in function SDL_ReportAssertion:SDL_assert.c(.text.SDL_ReportAssertion+0x30): error: undefined reference to ‘SDL_AtomicLock’
/Android/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld: CMakeFiles/SDL2.dir/SDL/src/SDL_assert.c.o: in function SDL_ReportAssertion:SDL_assert.c(.text.SDL_ReportAssertion+0x80): error: undefined reference to ‘SDL_AtomicUnlock’
/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld: CMakeFiles/SDL2.dir/SDL/src/audio/SDL_audio.c.o: in function bootstrap:SDL_audio.c(.data.rel.ro.bootstrap+0x0): error: undefined reference to ‘DUMMYAUD_bootstrap’
/Android/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld: CMakeFiles/SDL2.dir/SDL/src/stdlib/SDL_stdlib.c.o: in function SDL_atan:SDL_stdlib.c(.text.SDL_atan+0x14): error: undefined reference to 'atan’
collect2: ld returned 1 exit status
make[2]: *** […/libs/armeabi-v7a/libSDL2.so] Error 1
make[1]: *** [CMakeFiles/SDL2.dir/all] Error 2
make: *** [all] Error 2

Thank you for any ideas.
Michael

Alvin_Beach · November 23, 2013, 7:21pm

I haven’t tried using cmake, but you might need to link the math library? I
see undefined reference to sqrt, atan2, ceil, etc. Perhaps setup
CMakeLists.txt to emit ‘-lm’.

May not solve all the undefined references, but get rid of a few.

HTH,

AlvinOn Nov 23, 2013 2:58 PM, “Laz-Roc” wrote:

Have been away for awhile, but I’m back to tackle that Android + CMake
problem again.

Well, I think I’ve been successful building a static SDL2 library with
CMake, but wasn’t able to build an app so I don’t know if it’s working.
Vice versa, I couldn’t build a static library with the provided SDL2
README, but a demo with a shared library.

I’d like to build a shared library, anyway. So I slightly modified my
CMakeLists.txt http://pastebin.com/6mHJYcDf to building a shared
library by adding the SHARED tag.

Again, it creates the makefiles, and builds the object files. But I don’t
know how to solve the undefined reference error. Here are some of the
errors (I stripped similar errors; here is the full error messagehttp://pastebin.com/1mn2Utsd
):

Quote:

Linking C shared library …/libs/armeabi-v7a/libSDL2.so
/Android/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld:
CMakeFiles/SDL2.dir/SDL/src/SDL_assert.c.o: in function
SDL_ReportAssertion:SDL_assert.c(.text.SDL_ReportAssertion+0x30): error:
undefined reference to ‘SDL_AtomicLock’
/Android/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld:
CMakeFiles/SDL2.dir/SDL/src/SDL_assert.c.o: in function
SDL_ReportAssertion:SDL_assert.c(.text.SDL_ReportAssertion+0x80): error:
undefined reference to ‘SDL_AtomicUnlock’
/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld:
CMakeFiles/SDL2.dir/SDL/src/audio/SDL_audio.c.o: in function
bootstrap:SDL_audio.c(.data.rel.ro.bootstrap+0x0): error: undefined
reference to ‘DUMMYAUD_bootstrap’
/Android/android-toolchain/bin/…/lib/gcc/arm-linux-androideabi/4.6/…/…/…/…/arm-linux-androideabi/bin/ld:
CMakeFiles/SDL2.dir/SDL/src/stdlib/SDL_stdlib.c.o: in function
SDL_atan:SDL_stdlib.c(.text.SDL_atan+0x14): error: undefined reference to
’atan’
collect2: ld returned 1 exit status
make[2]: *** […/libs/armeabi-v7a/libSDL2.so] Error 1
make[1]: *** [CMakeFiles/SDL2.dir/all] Error 2
make: *** [all] Error 2

Thank you for any ideas.
Michael

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