Build failure for android on Windows

[yuanyazhen]

Describe the bug
cannot build android aar on Windows

To Reproduce
The first error happened in the second steps of Build stages (describled at android/Windows.md)

clang++.exe: warning: treating 'c' input as 'c++' when in C++ mode, this behavior is deprecated [-Wdeprecated] testCCompiler.c:2:3: error: "The CMAKE_C_COMPILER is set to a C++ compiler" # error "The CMAKE_C_COMPILER is set to a C++ compiler"

I check the toolchain cmake in the filament/build/toolchain-arm7-linux-android.cmake

if(WIN32)
set(COMPILER_SUFFIX ".cmd")
set(CMAKE_AR ${TOOLCHAIN}/bin/${ARCH}-ar.exe CACHE FILEPATH "Archiver")
endif()
set(CMAKE_C_COMPILER ${TOOLCHAIN}/bin/${ARCH}${API_LEVEL}-clang${COMPILER_SUFFIX})
set(CMAKE_CXX_COMPILER ${TOOLCHAIN}/bin/${ARCH}${API_LEVEL}-clang++${COMPILER_SUFFIX})
set(CMAKE_AR ${TOOLCHAIN}/bin/${ARCH}-ar${COMPILER_SUFFIX})
set(CMAKE_RANLIB ${TOOLCHAIN}/bin/${ARCH}-ranlib${COMPILER_SUFFIX})
set(CMAKE_STRIP ${TOOLCHAIN}/bin/${ARCH}-strip${COMPILER_SUFFIX})

But the NDK(r19) doesn't have the arm7-linux-android21-clang.cmd, so as the -ar.cmd or ranlib.

So i change the .cmake into follows

set(CMAKE_C_COMPILER ${TOOLCHAIN}/bin/clang.exe)
set(CMAKE_CXX_COMPILER ${TOOLCHAIN}/bin/clang++.exe)
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DANDROID --target=armv7a-linux-androideabi21 -fno-addrsig" CACHE STRING "Toolchain CFLAGS")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CMAKE_C_FLAGS} --stdlib=libc++" CACHE STRING "Toolchain CXXFLAGS")
set(CMAKE_AR ${TOOLCHAIN}/bin/${ARCH}-ar.exe)
set(CMAKE_RANLIB ${TOOLCHAIN}/bin/${ARCH}-ranlib.exe)
set(CMAKE_STRIP ${TOOLCHAIN}/bin/${ARCH}-strip.exe)

it successfully write makefiles.

But the ninja install complained

clang.exe: error: unsupported option '-fPIC' for target 'x86_64-w64-windows-gnu'
clang.exe: error: unsupported option '-fPIC' for target 'x86_64-w64-windows-gnu'

So i change the .cmake
set(CMAKE_POSITION_INDEPENDENT_CODE OFF) ON ->OFF

But the ninja still complains with -fPIC on materials.S.o, after some digging.
in the filament/CMakeLists.txt , i commented

set(LINUX_COMPILER_FLAGS
-fPIC
)

Now all the libs is build. [Maybe not all?]

So i went to generate filament-android.

but i got

D:/Projects/Filament_Windows/out/android-release/filament/lib/armeabi-v7a/libfilament.a(Engine.cpp.o):Engine.cpp:function filament::details::FEngine::init(): error: undefined reference to 'MATERIALS_PACKAGE' D:/Projects/Filament_Windows/out/android-release/filament/lib/armeabi-v7a/libfilament.a(Engine.cpp.o):Engine.cpp:function filament::details::FEngine::init(): error: undefined reference to 'MATERIALS_PACKAGE' D:/Projects/Filament_Windows/out/android-release/filament/lib/armeabi-v7a/libfilament.a(Skybox.cpp.o):Skybox.cpp:function filament::details::FSkybox::createMaterial(filament::details::FEngine&, bool): error: undefined reference to 'MATERIALS_PACKAGE' D:/Projects/Filament_Windows/out/android-release/filament/lib/armeabi-v7a/libfilament.a(Skybox.cpp.o):Skybox.cpp:function filament::details::FSkybox::createMaterial(filament::details::FEngine&, bool): error: undefined reference to 'MATERIALS_PACKAGE' clang++.exe: error: linker command failed with exit code 1 (use -v to see invocation) inja: build stopped: subcommand failed.

Now i am really stucked.

Several unsuccessful attemtion.

1. Try aarch64, similar issue with fPIE
2. try build libfilamat.a, and add it in the filament-android's CMakeList.txt, still failed.

So any suggestion?

[romainguy]

But the NDK(r19) doesn't have the arm7-linux-android21-clang.cmd, so as the -ar.cmd or ranlib.

What executables does the Windows NDK provide instead? Is it just clang.exe and clang++.exe?

[yuanyazhen]

Sorry for the typo.

The NDK(r19) does have the arm7-linux-android21-clang.cmd but it doesn't have clang++.cmd.

Moreover, in their clang.cmd, they are using clang++, that's why the cmake complains.

@echo off setlocal call :find_bin if "%1" == "-cc1" goto :L set "_BIN_DIR=" && %_BIN_DIR%clang++.exe --target=armv7a-linux-androideabi21 -fno-addrsig -stdlib=libc++ %*

for the -ar and ranlib, only .exe exists.

[romainguy]

Thank you, we'll fix the toolchain file.

[maikschulze]

Hi @CgGraphic , hi @romainguy

I went through similar issues and just a minute ago successfully compiled the filament libraries for Android.

1.) Broken ndk19b

From my understanding, the error "The CMAKE_C_COMPILER is set to a C++ compiler" is known and has been fixed in the NDK 19 and 20 branches:
android/ndk#920

I downloaded the appropriate NDK build here:
https://partner.android.com/partnerdash/d/partnerandroidbuild#p:id=buildlist&a=100621237&h=YnJhbmNoPWFvc3AtbmRrLXJlbGVhc2UtcjE5JnByb2R1Y3Q9d2luNjQ

, specifically android-ndk-5345600-windows-x86_64.zip

I've replaced the contents \android-sdk\ndk-bundle with zip. This fixed the compiler test.

2.) Adaptions to toolchain files

a) toolchain-aarch64-linux-android.cmake

I've commented out these three lines:

#set(CMAKE_AR           ${TOOLCHAIN}/bin/${ARCH}-ar${COMPILER_SUFFIX})
#set(CMAKE_RANLIB       ${TOOLCHAIN}/bin/${ARCH}-ranlib${COMPILER_SUFFIX})
#set(CMAKE_STRIP        ${TOOLCHAIN}/bin/${ARCH}-strip${COMPILER_SUFFIX})

b) toolchain-arm7-linux-android.cmake

I've adadapted these three lines:

set(CMAKE_AR           ${TOOLCHAIN}/bin/${AR_ARCH}-ar.exe)
set(CMAKE_RANLIB       ${TOOLCHAIN}/bin/${AR_ARCH}-ranlib.exe)
set(CMAKE_STRIP        ${TOOLCHAIN}/bin/${AR_ARCH}-strip.exe)

I hope this helps!

[yuanyazhen]

@maikschulze Thanks,

It seems that to successfully run the android sample, the CMakeLists.txt needs to be changed too.
Otherwise, the link will fail as I described.

I change line 321 from

WEBGL OR WIN32

to

WEBGL OR WIN32 OR ANDROID

Now, the android samples run successfully.

[romainguy]

@maikschulze Thank you, I'm about to upload a change with the proper fixes.

[romainguy]

You can try PR #968 to see if it fixes your issues with the new NDK.

[maikschulze]

@romainguy ,
thank you very much for the quick fixes. I can confirm that this proper approach works. The Android samples also run successfully on x86 and armv7.