doc: advertise clang-cl support.

README.md

@@ -55,7 +55,7 @@ SUPPORTED PLATFORMS
 ===================
 
 -   **Linux** and embedded Linux
--   **Windows**, **Windows RT** (Store/Phone)
+-   **Windows** with MSVC, clang-cl and MinGW, **Windows RT** (Store/Phone)
 -   **macOS**, **iOS**
 -   **Android**
 -   **Web** ([asm.js](http://asmjs.org/) or [WebAssembly](http://webassembly.org/)),

doc/building.dox

@@ -39,7 +39,7 @@ Minimal set of tools and libraries required for building is:
 
 -   C++ compiler with good C++11 support. Compilers which are tested to have
     everything needed are **GCC** >= 4.8.1, **Clang** >= 3.3 and **MSVC**
-    >= 2015. On Windows you can also use **MinGW-w64**.
+    >= 2015. On Windows you can also use **Clang-CL** or **MinGW-w64**.
 -   **CMake** >= 3.4
 -   **Corrade** --- Plugin management and utility library. See
     @ref building-corrade "Corrade download and installation guide" for more
@@ -384,8 +384,8 @@ want to set `CMAKE_INSTALL_RPATH` to `lib/` subdir of given prefix (e.g.
 
 @subsection building-windows Building on Windows
 
-On Windows you can use either MSVC or the MinGW-w64 compiler. It's then up to
-you whether you will use QtCreator, Visual Studio or another IDE or do the
+On Windows you can use MSVC, clang-cl or the MinGW-w64 compiler. It's then up
+to you whether you will use QtCreator, Visual Studio or another IDE or do the
 build from a command line. Note that for most convenient usage it's best use
 some dedicated directory (e.g. `C:/Sys`) for installing dependencies instead of
 putting each dependency to its own directory in `C:/Program Files` or

doc/changelog.dox

@@ -38,6 +38,9 @@ See also:
 
 @section changelog-latest Changes since 2019.10
 
+-   Clang-CL is now a supported compiler on Windows. See also
+    @ref platforms-windows-clang-cl and [mosra/magnum#227](https://github.com/mosra/magnum/issues/227).
+
 @subsection changelog-latest-new New features
 
 @subsubsection changelog-latest-new-gl GL library

doc/platforms-windows.dox

@@ -143,6 +143,45 @@ console window lurking in the background. This can be fixed by creating your
 executable with @cmake add_executable(... WIN32 ...) @ce and linking to the
 @ref main "Corrade::Main" library. See its documentation for more information.
 
+@section platforms-windows-clang-cl Using Clang-CL
+
+As an alternative to MSVC it's possible to use [Clang-CL](https://clang.llvm.org/docs/UsersManual.html#clang-cl).
+Compared to MinGW it is fully ABI-compatible with MSVC, sharing the same STL
+implementation, and thus you can freely mix and match libraries built by either
+of them.
+
+If you already have MSVC 2019, clang-cl is available as an optional install
+component. Configuring your project to be used with e.g. Ninja could then look
+similarly to the following. Custom clang-cl installations work as well of
+course, adapt the paths as necessary:
+
+@code{.bat}
+C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Auxiliary/Build/vcvarsall.bat" x64
+
+cmake .. ^
+    -DCMAKE_C_COMPILER="C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/clang-cl.exe" ^
+    -DCMAKE_CXX_COMPILER="C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/clang-cl.exe" ^
+    -DCMAKE_LINKER="C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/Llvm/bin/lld-link.exe" ^
+    -DCMAKE_CXX_FLAGS="-m64" ^
+    -G Ninja
+@endcode
+
+CMake is currently [having issues propagating correct bitness to clang-cl](https://gitlab.kitware.com/cmake/cmake/issues/16259)
+when using Ninja, which means you may need to explicitly pass either `-m64` or
+`-m32` to Clang. In the above case, `vcvarsall.bat` was called with the `x64`
+parameter but the Clang bundled with Visual Studio is 32-bit and thus defaults
+to 32-bit builds. Additionally, if your code needs to use exceptions (Magnum
+itself doesn't, but @ref Corrade::TestSuite relies on them to report failures
+in tests), you may need to explicitly pass `/EHs` via `CMAKE_CXX_FLAGS` as
+exceptions are currently [disabled by default](https://github.com/catchorg/Catch2/issues/1113).
+
+While Magnum itself is tested to work with this compiler, be prepared that you
+might run into exciting new issues that aren't present with MSVC, MinGW or
+Clang alone. In dire situations, you can use @ref CORRADE_TARGET_CLANG_CL to
+add compiler-specific workarounds.
+
+More information on [the Microsoft C++ Team Blog](https://devblogs.microsoft.com/cppblog/clang-llvm-support-in-visual-studio/).
+
 @section platforms-windows-rt Windows RT
 
 Windows RT is a restricted subset of Windows API, used for UWP / "Metro" /