I’m compiling a library which links to pytorch and is then used to build an iOS app.
However when i build the project in XCode i get the following errors:
Undefined symbols for architecture x86_64:
"_cpuinfo_get_processors_count", referenced from:
      caffe2::getDefaultNumThreads() in libtorch_cpu.a(ThreadPool.cc.o)
"_pthreadpool_get_threads_count", referenced from:
      caffe2::PThreadPool::get_thread_count() const in libtorch_cpu.a(pthreadpool-cpp.cc.o)
  "_pthreadpool_create", referenced from:
      caffe2::PThreadPool::PThreadPool(unsigned long) in libtorch_cpu.a(pthreadpool-cpp.cc.o)
      caffe2::PThreadPool::set_thread_count(unsigned long) in libtorch_cpu.a(pthreadpool-cpp.cc.o)
  "_pthreadpool_destroy", referenced from:
      caffe2::PThreadPool::PThreadPool(unsigned long) in libtorch_cpu.a(pthreadpool-cpp.cc.o)
  "_pthreadpool_parallelize_1d", referenced from:
      caffe2::PThreadPool::run(std::__1::function<void (unsigned long)> const&, unsigned long) in libtorch_cpu.a(pthreadpool-cpp.cc.o)
  "_cpuinfo_initialize", referenced from:
      caffe2::getDefaultNumThreads() in libtorch_cpu.a(ThreadPool.cc.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Checking the libtorch_cpu.a using nm I found that _cpuinfo_initialize and _cpuinfo_get_processors_count are undefined.
To build my pytorch libraries I’ve set NO_API to OFF as well as BUILD_MOBILE_AUTOGRAD to ON in the root CMakeLists file of pytorch.
I then run IOS_PLATFORM=SIMULATOR BUILD_PYTORCH_MOBILE=1 BUILD_LITE_INTERPRETER=0 ./scripts/build_ios.sh.
When building my library, I link to libtorch_cpu.a and libc10.a
Any ideas ?