Does not work with nvcc on Windows

[ezyang]

This probably won't get fixed, but we're posting this here to let anyone else who might be interested in using this know.

[akrzemi1]

Can we see the minimal code and the error message?

[ezyang]

#include <Optional/optional.hpp>

void f() {
	std::experimental::optional<int> x;
}

I built it with both normal MSVC compiler, and nvcc.

@echo off
call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat" x86_amd64
cl.exe -I. -c kernel.cc
"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.0\bin\nvcc" -I. -c kernel.cu

The normal MSVC compiler passes. nvcc fails with:

**********************************************************************
** Visual Studio 2017 Developer Command Prompt v15.4.5
** Copyright (c) 2017 Microsoft Corporation
**********************************************************************
[vcvarsall.bat] Environment initialized for: 'x86_x64'
kernel.cc
C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.11.25503\include\xlocale(314): warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc
C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.11.25503\include\iosfwd(292): warning C4577: 'noexcept' used with no exception handling mode specified; termination on exception is not guaranteed. Specify /EHsc
kernel.cu
.\Optional/optional.hpp(413): error C2614: 'std::experimental::optional<int>': illegal member initialization: 'OptionalBase' is not a base or member
.\Optional/optional.hpp(413): note: while compiling class template member function 'std::experimental::optional<int>::optional(void) noexcept'
kernel.cu(4): note: see reference to function template instantiation 'std::experimental::optional<int>::optional(void) noexcept' being compiled
kernel.cu(4): note: see reference to class template instantiation 'std::experimental::optional<int>' being compiled

[ezyang]

There is a workaround for the problem at pytorch/pytorch#10909