From d2255cb8d45e8ee6a907a73dc2a9169ac5c72465 Mon Sep 17 00:00:00 2001
From: David Chisnall <github@theravensnest.org>
Date: Wed, 27 Feb 2019 16:31:38 +0000
Subject: [PATCH] Add Windows build instructions.

---
 README.windows | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 README.windows

diff --git a/README.windows b/README.windows
new file mode 100644
index 0000000..b704293
--- /dev/null
+++ b/README.windows
@@ -0,0 +1,36 @@
+Building on Windows
+===================
+
+The runtime can build on Windows with either Ninja or msbuild.
+Ninja is strongly preferred, but if you wish to debug with Visual Studio then you will need to use msbuild.
+
+To compile with msbuild, you must install the (LLVM toolchain)[https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.llvm-toolchain] and then, from a Visual Studio command prompt:
+
+```
+> mkdir build
+> cd build
+> cmake -G "Visual Studio 15 2017 Win64" -T LLVM -DASSEMBLER=path/to/clang-cl.exe ..
+> set CCC_OVERRIDE_OPTIONS=x-TC x-TP x/TC x/TP
+> cmake --build .
+```
+
+This will give you a solution file that you can open in Visual Studio.
+If you don't wish to use the Visual Studio IDE, then you can compile with Ninja:
+
+```
+> mkdir build
+> cd build
+> cmake -G Ninja -DCMAKE_C_COMPILER=path/to/clang-cl.exe -DCMAKE_CXX_COMPILER=path/to/clang-cl.exe ..
+> set CCC_OVERRIDE_OPTIONS=x-TC x-TP x/TC x/TP
+> ninja
+```
+
+Unfortunately, CMake insists on adding flags so that force cl.exe to treat the input as C or C++.
+The `CCC_OVERRIDE_OPTIONS` environment variable strips these flags off.
+
+Debugging
+---------
+
+The tests will all fail on Windows because they will not find objc.dll.
+To fix this, copy objc.dll into the `Tests` build directory.
+Alternatively, from within Visual Studio, set the working directory for the test to the `Debug` directory.