Hi,
I’m following this example: pytorch-android-cpp-demo 10
and I successfully compiled libtorch for Android but I’m having problems linking the static libs to my c++ project.
Here are the details:
Steps

Compiling libtorch for Android on  Linux  as explained in the example using:


Ubuntu 20.04
NDK 21 (for Linux 64b)
Cmake 3.16.3
The resulting files are  static (.a)  files.


Linking torch .a files to an Android c++ project on  Windows  using:


NDK 21 (for Windows)
Android .mk files (I can’t use Cmake)

Compiled for armeabi-v7a arch. (32b)
Used  APP_STL := c++_static

Used prebuilt and LOCAL_STATIC_LIBRARIES to link the torch libraries:



LOCAL_STATIC_LIBRARIES += c10-prebuilt
LOCAL_STATIC_LIBRARIES += torch-prebuilt
LOCAL_STATIC_LIBRARIES += torch_cpu-prebuilt

include $(CLEAR_VARS)
LOCAL_MODULE := c10-prebuilt
LOCAL_SRC_FILES := C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libc10.a
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := torch-prebuilt
LOCAL_SRC_FILES := C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch.a
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := torch_cpu-prebuilt
LOCAL_SRC_FILES := C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch_cpu.a
include $(PREBUILT_STATIC_LIBRARY)

Error Message
This is the error message I’m getting when compiling my project:
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/core/ivalue.cpp:430: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::Device const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/core/ivalue.cpp:489: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::Device const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/aten/src/ATen/Functions.cpp:145: error: undefined reference to ‘c10::toString(c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/aten/src/ATen/Functions.cpp:165: error: undefined reference to ‘c10::toString(c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/core/TensorOptions.h:252: error: undefined reference to ‘c10::get_default_dtype()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/core/TensorOptions.h:252: error: undefined reference to ‘c10::get_default_dtype()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/aten/src/ATen/Functions.cpp:289: error: undefined reference to ‘c10::toString(c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/aten/src/ATen/Functions.cpp:827: error: undefined reference to ‘c10::toString(c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DeviceType)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/core/impl/DeviceGuardImplInterface.h:0: error: undefined reference to ‘c10::impl::device_guard_impl_registry’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DeviceType)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/jit/ir/constants.cpp:110: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::Device const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/jit/ir/constants.cpp:177: error: undefined reference to ‘c10::Device::Device(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator > const&)’
/mnt/c/Android/linux/android-ndk-r21d/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/memory:0: error: undefined reference to ‘c10::detail::deleteNothing(void*)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/intrusive_ptr.h:0: error: undefined reference to ‘c10::detail::deleteNothing(void*)’
/mnt/c/Android/linux/android-ndk-r21d/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/new:0: error: undefined reference to ‘c10::detail::deleteNothing(void*)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/core/TensorOptions.h:252: error: undefined reference to ‘c10::get_default_dtype()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/jit/serialization/unpickler.cpp:399: error: undefined reference to ‘c10::Device::Device(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator > const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/jit/serialization/unpickler.cpp:425: error: undefined reference to ‘c10::DeviceTypeName(c10::DeviceType, bool)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/jit/serialization/unpickler.cpp:542: error: undefined reference to ‘c10::Device::Device(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator > const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/jit/frontend/function_schema_parser.cpp:251: error: undefined reference to ‘c10::Device::Device(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator > const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/core/Generator.h:102: error: undefined reference to ‘c10::GeneratorImpl::device() const’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/core/Generator.h:102: error: undefined reference to ‘c10::GeneratorImpl::device() const’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DeviceType)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DeviceType)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::Device const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/native/BinaryOps.cpp:173: error: undefined reference to ‘c10::get_default_dtype()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/core/Generator.h:102: error: undefined reference to ‘c10::GeneratorImpl::device() const’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/core/Generator.h:102: error: undefined reference to ‘c10::GeneratorImpl::device() const’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::TensorOptions const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/native/TensorShape.cpp:73: error: undefined reference to ‘c10::GetAllocator(c10::DeviceType const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/native/TypeProperties.cpp:84: error: undefined reference to ‘c10::get_default_complex_dtype()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/core/LegacyTypeDispatch.h:0: error: undefined reference to ‘c10::detail::deleteNothing(void*)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/native/xnnpack/Factory.cpp:17: error: undefined reference to ‘c10::GetDefaultMobileCPUAllocator()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/native/xnnpack/Factory.cpp:41: error: undefined reference to ‘c10::GetDefaultMobileCPUAllocator()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/TH/THAllocator.cpp:25: error: undefined reference to ‘c10::GetCPUAllocator()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/TH/THAllocator.cpp:571: error: undefined reference to ‘c10::reportMemoryUsageToProfiler(void*, long long, c10::Device)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/quantized/Quantizer.cpp:75: error: undefined reference to ‘c10::GetDefaultMobileCPUAllocator()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/aten/src/ATen/native/cpu/BinaryOpsKernel.cpp.DEFAULT.cpp:78: error: undefined reference to ‘c10::Scalar::operator-() const’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/caffe2/serialize/inline_container.cc:222: error: undefined reference to ‘c10::GetCPUAllocator()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/CPUGeneratorImpl.cpp:18: error: undefined reference to ‘c10::detail::getNonDeterministicRandom(bool)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/CPUGeneratorImpl.cpp:43: error: undefined reference to ‘c10::GeneratorImpl::GeneratorImpl(c10::Device, c10::DispatchKeySet)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/CPUGeneratorImpl.cpp:73: error: undefined reference to ‘c10::detail::getNonDeterministicRandom(bool)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/CPUGeneratorImpl.cpp:43: error: undefined reference to ‘c10::GeneratorImpl::GeneratorImpl(c10::Device, c10::DispatchKeySet)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/PTThreadPool.h:13: error: undefined reference to ‘c10::ThreadPool::ThreadPool(int, int, std::__ndk1::function<void ()>)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/ParallelThreadPoolNative.cpp:26: error: undefined reference to ‘c10::ThreadPoolRegistry()’
/mnt/c/Android/linux/android-ndk-r21d/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/memory:2133: error: undefined reference to ‘c10::ThreadPool::~ThreadPool()’
/mnt/c/Android/linux/android-ndk-r21d/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/memory:2133: error: undefined reference to ‘c10::ThreadPool::~ThreadPool()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/PTThreadPool.h:8: error: undefined reference to ‘c10::ThreadPool::~ThreadPool()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/PTThreadPool.h:14: error: undefined reference to ‘c10::setThreadName(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator >)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/ParallelThreadPoolNative.cpp:48: error: undefined reference to ‘c10::ThreadPoolRegistry()’
C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch_cpu.a(ParallelThreadPoolNative.cpp.o):ParallelThreadPoolNative.cpp:vtable for at::PTThreadPool: error: undefined reference to ‘c10::ThreadPool::run(std::__ndk1::function<void ()>)’
C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch_cpu.a(ParallelThreadPoolNative.cpp.o):ParallelThreadPoolNative.cpp:vtable for at::PTThreadPool: error: undefined reference to ‘c10::ThreadPool::size() const’
C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch_cpu.a(ParallelThreadPoolNative.cpp.o):ParallelThreadPoolNative.cpp:vtable for at::PTThreadPool: error: undefined reference to ‘c10::ThreadPool::numAvailable() const’
C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch_cpu.a(ParallelThreadPoolNative.cpp.o):ParallelThreadPoolNative.cpp:vtable for at::PTThreadPool: error: undefined reference to ‘c10::ThreadPool::inThreadPool() const’
C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch_cpu.a(ParallelThreadPoolNative.cpp.o):ParallelThreadPoolNative.cpp:vtable for at::PTThreadPool: error: undefined reference to ‘c10::ThreadPool::~ThreadPool()’
C:/REPOSITORIES/pytorch-android-cpp-demo/pytorch/build_android/install/lib/libtorch_cpu.a(ParallelThreadPoolNative.cpp.o):ParallelThreadPoolNative.cpp:typeinfo for at::PTThreadPool: error: undefined reference to ‘typeinfo for c10::ThreadPool’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DispatchKeySet)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/ThreadLocalState.cpp:11: error: undefined reference to ‘c10::ThreadLocalDebugInfo::current()’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/ATen/ThreadLocalState.cpp:32: error: undefined reference to ‘c10::ThreadLocalDebugInfo::_forceCurrentDebugInfo(std::__ndk1::shared_ptrc10::ThreadLocalDebugInfo const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/util/StringUtil.h:37: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::DispatchKey)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/TH/THGeneral.cpp:156: error: undefined reference to ‘c10::alloc_cpu(unsigned int)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/aten/src/TH/THGeneral.cpp:188: error: undefined reference to ‘c10::free_cpu(void*)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/autograd/engine.cpp:0: error: undefined reference to ‘c10::impl::device_guard_impl_registry’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/autograd/engine.cpp:621: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::TensorOptions const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/autograd/engine.cpp:621: error: undefined reference to ‘c10::operator<<(std::__ndk1::basic_ostream<char, std::__ndk1::char_traits >&, c10::TensorOptions const&)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/torch/csrc/autograd/engine.cpp:0: error: undefined reference to ‘c10::impl::device_guard_impl_registry’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/core/impl/InlineEvent.h:60: error: undefined reference to ‘c10::DeviceTypeName(c10::DeviceType, bool)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/core/impl/InlineEvent.h:60: error: undefined reference to ‘c10::DeviceTypeName(c10::DeviceType, bool)’
/mnt/c/REPOSITORIES/pytorch-android-cpp-demo/pytorch/c10/core/impl/InlineEvent.h:76: error: undefined reference to ‘c10::DeviceTypeName(c10::DeviceType, bool)’
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [c:/Android/android-ndk-r21d/build//…/build/core/build-binary.mk:738: C:/REPOSITORIES/SVLTemp2/obj/local/armeabi-v7a/dczoom_native] Error 1
Can you please help me figure out what is wrong?
Thank you