Make CI and the nightly release work on Windows

[Michael-F-Bryan]

Closes #101.

[Michael-F-Bryan]

I believe this is the issue we are running into: rust-lang/rust-bindgen#1797 (comment)

[Michael-F-Bryan]

I made some progress on this by playing around on my Windows VM...

When you see something like this:

C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xstddef:283:22: error: 'auto' return without trailing return type; deduced return types are a C++14 extension, err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:1427:16: error: constexpr function's return type 'void' is not a literal type, err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:1476:22: error: 'auto' return without trailing return type; deduced return types are a C++14 extension, err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:1481:16: error: no viable conversion from returned value of type 'std::_Distance_unknown' to function return type 'int', err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:1783:27: error: constexpr function's return type 'void' is not a literal type, err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:1788:20: error: constexpr function's return type 'void' is not a literal type, err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:1801:20: error: constexpr function's return type 'void' is not a literal type, err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:3799:18: error: 'auto' return without trailing return type; deduced return types are a C++14 extension, err: true
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30037\include\xutility:3903:27: error: constexpr function's return type 'void' is not a literal type, err: true
  fatal error: too many errors emitted, stopping now [-ferror-limit=], err: true
  thread 'main' panicked at 'Unable to generate bindings: ()', C:\Users\runneradmin\.cargo\registry\src\github.aaakk.us.kg-1ecc6299db9ec823\tflite-0.9.6\build.rs:237:40

It's because bindgen is defaulting to an older version of the C++ CTL on Windows. You can fix this by asking it to pass -std=c++17 to libclang (echo "BINDGEN_EXTRA_CLANG_ARGS=-std=c++17" >> $env:GITHUB_ENV).

Next the Microsoft compiler, cl, will complain about a dodgy argument.

  running: "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Enterprise\\VC\\Tools\\MSVC\\14.29.30037\\bin\\HostX64\\x64\\cl.exe" "-nologo" "-MD" "-Z7" "-Brepro" "-I" "C:\\Users\\runneradmin\\.cargo\\registry\\src\\github.aaakk.us.kg-1ecc6299db9ec823\\tflite-0.9.6" "-I" "C:\\Users\\runneradmin\\.cargo\\registry\\src\\github.aaakk.us.kg-1ecc6299db9ec823\\tflite-0.9.6\\submodules\\tensorflow" "-I" "C:\\Users\\runneradmin\\.cargo\\registry\\src\\github.aaakk.us.kg-1ecc6299db9ec823\\tflite-0.9.6\\submodules\\downloads/flatbuffers/include" "-W4" "-fPIC" "-std=c++14" "-Wno-sign-compare" "-DGEMMLOWP_ALLOW_SLOW_SCALAR_FALLBACK" "-DFLATBUFFERS_POLYMORPHIC_NATIVETABLE" "-FoD:\\a\\rune\\rune\\target\\debug\\build\\tflite-e183d799789c93c3\\out\\rust_cpp\\cpp_closures.o" "-c" "D:\\a\\rune\\rune\\target\\debug\\build\\tflite-e183d799789c93c3\\out\\rust_cpp\\cpp_closures.cpp"
  cargo:warning=cl : Command line error D8021 : invalid numeric argument '/Wno-sign-compare'
  exit code: 2

I resolved that by just telling the build to use clang++ (which we need for bindgen anyway) instead of cl.

> $env:CC = "clang"
> $env:CXX = "clang++"

This isn't 100% perfect though because CMake decides to compile position-independent code (-fPIC), which isn't a thing on x86_64-pc-windows-msvc.

running: "clang++" "-O0" "-ffunction-sections" "-fdata-sections" "-g" "-fno-omit-frame-pointer" "--target=x86_64-pc-windows-msvc" "-I" "C:\\Users\\Michael\\Documents\\tflite-rs" "-I" "C:\\Users\\Michael\\Documents\\tflite-rs\\submodules\\tensorflow" "-I" "C:\\Users\\Michael\\Documents\\tflite-rs\\submodules\\downloads/flatbuffers/include" "-Wall" "-Wextra" "-fPIC" "-std=c++14" "-Wno-sign-compare" "-DGEMMLOWP_ALLOW_SLOW_SCALAR_FALLBACK" "-DFLATBUFFERS_POLYMORPHIC_NATIVETABLE" "-o" "C:\\Users\\Michael\\Documents\\tflite-rs\\target\\x86_64-pc-windows-msvc\\debug\\build\\tflite-788407d034bca9a4\\out\\rust_cpp\\cpp_closures.o" "-c" "C:\\Users\\Michael\\Documents\\tflite-rs\\target\\x86_64-pc-windows-msvc\\debug\\build\\tflite-788407d034bca9a4\\out\\rust_cpp\\cpp_closures.cpp"
cargo:warning=clang++: error: unsupported option '-fPIC' for target 'x86_64-pc-windows-msvc'

[Michael-F-Bryan]

I'm going to close this for now. Windows builds should be naturally handled when librunecoral has Windows support (hotg-ai/librunecoral#2) and we fully remove the tflite crate.