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+How to Build Erlang/OTP on Windows
+==================================
+
+Introduction
+------------
+
+This HOWTO describes how to build from Cygwin, MSYS or MSYS2 environments,
+we currently use WSL to build and test Erlang/OTP so the instructions
+herein is no longer tested/used by the OTP team.
+
+Using Cygwin, MSYS or MSYS2 as a build environment will be removed in
+the future.
+
+This section describes how to build the Erlang emulator and the OTP
+libraries on Windows. Note that the Windows binary releases are still
+a preferred alternative if one does not have Microsoft’s development
+tools and/or don’t want to install Cygwin, MSYS or MSYS2.
+
+The instructions apply to versions of Windows supporting the Cygwin 
+emulated gnuish environment or the MSYS or MSYS2 ditto. We’ve built on 
+the following platforms: Windows 2012, Windows 7, Windows 8 and Windows 10. 
+It’s probably possible to build on older platforms too, but you might 
+not be able to install the appropriate Microsoft SDK, Visual Studio or 
+OpenSSL, in which case you will need to go back to earlier compilers etc.  
+
+The procedure described uses either Cygwin, MSYS or MSYS2 as a build 
+environment. You run the bash shell in Cygwin/MSYS/MSYS2 and use the gnu 
+make/configure/autoconf etc to do the build. The emulator C-source code 
+is, however, mostly compiled with Microsoft Visual C++™, producing a 
+native Windows binary. This is the same procedure as we use to build the 
+pre-built binaries. Why we use VC++ and not gcc is explained further in 
+the FAQ section. 
+
+If you are not familiar with Cygwin, MSYS, MSYS2 or a Unix environment, 
+you’ll probably need to read up a bit on how that works. There are plenty of 
+documentation about this online.
+
+These instructions apply for both 32-bit and 64-bit Windows. Note that even 
+if you build a 64-bit version of Erlang, most of the directories and files 
+involved are still named win32. Some occurances of the name win64 are 
+however present. The installation file for a 64-bit Windows version of 
+Erlang, for example, is `otp_win64_%OTP-REL%.exe`.
+
+If you feel comfortable with the environment and build
+system, and have all the necessary tools, you have a great opportunity
+to make the Erlang/OTP distribution for Windows better. Please submit
+any suggestions to our [JIRA] [2] and patches to our [git project] [3] to let
+them find their way into the next version of Erlang. If making changes
+to the build system (like makefiles etc) please bear in mind that the
+same makefiles are used on Unix/VxWorks, so that your changes
+don't break other platforms. That of course goes for C-code too; system
+specific code resides in the `$ERL_TOP/erts/emulator/sys/win32` and
+`$ERL_TOP/erts/etc/win32` directories mostly. The
+`$ERL_TOP/erts/emulator/beam` directory is for common code.
+
+We've used this build procedure for a couple of
+releases, and it has worked fine for us. Still, there might be all
+sorts of troubles on different machines and with different
+setups. We'll try to give hints wherever we've encountered difficulties,
+but please share your experiences by using the [erlang-questions] [1]
+mailing list. We cannot, of course, help everyone with all
+their issues, so please try to solve such issues and submit
+solutions/workarounds.
+
+Lets go then! We’ll start with a short version of the setup procedure, 
+followed by some FAQ, and then we’ll go into more details of the setup. 
+
+
+Short Version
+-------------
+
+In the following sections, we've described as much as we could about the 
+installation of the tools needed. Once the tools are installed, building 
+is quite easy. We have also tried to make these instructions understandable 
+for people with limited Unix experience. Cygwin/MSYS/MSYS2 is a whole new 
+environment to some Windows users, why careful explanation of environment 
+variables etc seemed to be in place. 
+
+This is the short story though, for the experienced and impatient:
+
+    *   Get and install complete Cygwin (latest), complete MinGW with MSYS or 
+        complete MSYS2
+
+    *   Install Visual Studio 12.0 (2013)
+
+    *   Install Microsofts Windows SDK 8.1 
+
+    *   Get and install Sun's JDK 1.6.0 or later
+
+    *   Get and install NSIS 2.01 or later (up to 2.46 tried and working)
+
+    *   Get, build and install OpenSSL 0.9.8r or later (up to 1.0.2d
+        tried & working) with static libs.
+
+    *   Get the Erlang source distribution (from
+        <http://www.erlang.org/download.html>) and unpack with 
+        Cygwin's/MSYS's/MSYS2's `tar`.
+
+    *   Set `ERL_TOP` to where you unpacked the source distribution
+
+    *   `$ cd $ERL_TOP`
+
+    *   Modify PATH and other environment variables so that all these tools
+        are runnable from a bash shell. Still standing in `$ERL_TOP`, issue
+        the following commands (for 32-bit Windows, remove the x64 from the 
+        first row and change `otp_win64_%OTP-REL%` to `otp_win32_%OTP-REL%` on
+        the last row):
+
+            $ eval `./otp_build env_win32 x64`
+            $ ./otp_build autoconf
+            $ ./otp_build configure
+            $ ./otp_build boot -a
+            $ ./otp_build release -a
+            $ ./otp_build installer_win32
+            $ release/win32/otp_win64_%OTP-REL% /S
+
+    Voila! `Start->Programs->Erlang OTP %OTP-REL%->Erlang` starts the Erlang
+    Windows shell.
+
+
+Frequently Asked Questions
+--------------------------
+
+*   Q: So, now I can build Erlang using GCC on Windows?
+
+    A: No, unfortunately not. You'll need Microsoft's Visual C++
+    still. A Bourne-shell script (cc.sh) wraps the Visual C++ compiler
+    and runs it from within the Cygwin environment. All other tools
+    needed to build Erlang are free-ware/open source, but not the C
+    compiler. The Windows SDK is however enough to build Erlang, you
+    do not need to buy Visual C++, just download the SDK (SDK version
+    8.1 == Visual studio 2013).
+
+*   Q: Why haven't you got rid of VC++ then, you \*\*\*\*\*\*?
+
+    A: Well, partly because it's a good compiler - really! Actually it's
+    been possible in late R11-releases to build using mingw instead of
+    visual C++ (you might see the remnants of that in some scripts and
+    directories). Unfortunately the development of the SMP version for
+    Windows broke the mingw build and we chose to focus on the VC++ build
+    as the performance has been much better in the VC++ versions. The
+    mingw build will possibly be back, but as long as VC++ gives better
+    performance, the commercial build will be a VC++ one.
+
+*   Q: OK, you need VC++, but now you've started to demand a quite recent
+    (and expensive) version of Visual Studio. Why?
+
+    A: Well, it's not expensive, it's free (as in free beer). Just
+    download and install the latest Windows SDK from Microsoft and all
+    the tools you need are there. The included debugger (WinDbg) is
+    also quite usable. That's what I used when porting Erlang to 64bit
+    Windows. Another reason to use later Microsoft compilers is 
+    DLL compatibility. DLL's using a new version of the standard
+    library might not load if the VM is compiled with an old VC++
+    version. So we should aim to use the latest freely available SDK
+    and compiler.
+
+*   Q: Can/will I build a Cygwin binary with the procedure you describe?
+
+    A: No, the result will be a pure Windows binary, and as far as I know,
+    it's not possible to make a Cygwin binary yet. That is of course
+    something desirable, but there are still some problems with the
+    dynamic linking (dynamic Erlang driver loading) as well as the TCP/IP
+    emulation in Cygwin, which, I'm sure of, will improve, but still has
+    some problems. Fixing those problems might be easy or might be hard.
+    I suggest you try yourself and share your experience. No one would be
+    happier if a simple `./configure && make` would produce a fully fledged
+    Cygwin binary. 
+
+*   Q: Hah, I saw you, you used GCC even though you said you didn't!
+
+    A: OK, I admit, one of the files is compiled using Cygwin's or
+    MinGW's GCC and the resulting object code is then converted to MS
+    VC++ compatible coff using a small C hack. It's because that
+    particular file, `beam_emu.c` benefits immensely from being able
+    to use the GCC labels-as-values extension, which boosts emulator
+    performance by up to 50%. That does unfortunately not (yet) mean
+    that all of OTP could be compiled using GCC. That particular
+    source code does not do anything system specific and actually is
+    adopted to the fact that GCC is used to compile it on Windows.
+
+*   Q: So now there's a MS VC++ project file somewhere and I can build OTP
+    using the nifty VC++ GUI?
+
+    A: No, never. The hassle of keeping the project files up to date and
+    do all the steps that constitute an OTP build from within the VC++ GUI
+    is simply not worth it, maybe even impossible. A VC++ project
+    file for Erlang/OTP will never happen.
+
+*   Q: So how does it all work then?
+
+    A: Cygwin, MSYS or MSYS2 is the environment, which closely resembles the
+    environment found on any Unix machine. It's almost like you had a
+    virtual Unix machine inside Windows. Configure, given certain
+    parameters, then creates makefiles that are used by the
+    environment's gnu-make to built the system. Most of the actual
+    compilers etc are not, however, Cygwin/MSYS/MSYS2 tools, so we've written
+    a couple of wrappers (Bourne-shell scripts), which reside in
+    `$ERL_TOP/etc/win32/cygwin_tools` and
+    `$ERL_TOP/etc/win32/msys_tools`. They all do conversion of
+    parameters and switches common in the Unix environment to fit the
+    native Windows tools. Most notable is of course the paths, which
+    in Cygwin/MSYS/MSYS2 are Unix-like paths with "forward slashes" (/) and
+    no drive letters. The Cygwin specific command `cygpath` is used
+    for most of the path conversions in a Cygwin environment. Other
+    tools are used (when needed) in the corresponding MSYS and MSYS2
+    environment. Luckily most compilers accept forward slashes instead
+    of backslashes as path separators, but one still have to get the drive
+    letters etc right, though. The wrapper scripts are not general in
+    the sense that, for example, cc.sh would understand and translate
+    every possible gcc option and pass correct options to
+    cl.exe. The principle is that the scripts are powerful enough to
+    allow building of Erlang/OTP, no more, no less. They might need
+    extensions to cope with changes during the development of Erlang, and
+    that's one of the reasons we made them into shell-scripts and not
+    Perl-scripts. We believe they are easier to understand and change
+    that way.
+
+    In `$ERL_TOP`, there is a script called `otp_build`. That script handles
+    the hassle of giving all the right parameters to `configure`/`make` and
+    also helps you set up the correct environment variables to work with
+    the Erlang source under Cygwin/MSYS/MSYS2.
+
+*   Q: You use and need Cygwin, but then you haven't taken the time to
+    port Erlang to the Cygwin environment but instead focus on your
+    commercial release, is that really ethical?
+
+    A: No, not really, but see this as a step in the right direction. 
+
+*   Q: Can I build something that looks exactly as the commercial release?
+
+    A: Yes, we use the exact same build procedure.
+
+*   Q: Which version of Cygwin/MSYS/MSYS2 and other tools do you use then?
+
+    A: For Cygwin, MSYS and MSYS2 alike, we try to use the latest releases
+    available when building. What versions you use shouldn't really
+    matter. We try to include workarounds for the bugs we've found in
+    different Cygwin/MSYS/MSYS2 releases. Please help us add workarounds
+    for new Cygwin/MSYS/MSYS2-related bugs as soon as you encounter
+    them. Also please do submit bug reports to the appropriate Cygwin, MSYS
+    and/or MSYS2 developers. The GCC we used for %OTP-REL% was version
+    4.8.1 (MinGW 32bit) and 4.8.5 (MSYS2 64bit). We used  VC++ 12.0 
+    (i.e. Visual studio 2013), Sun's JDK 1.6.0\_45 (32bit) and Sun's
+    JDK 1.7.0\_1 (64bit), NSIS 2.46, and Win32 OpenSSL 1.0.2d. Please
+    read the next section for details on what you need.
+
+*   Q: Can you help me setup X in Cygwin/MSYS/MSYS2?
+
+    A: No, unfortunately we haven't got time to help with Cygwin/MSYS/MSYS2 
+    related user problems, please read related websites, newsgroups and
+    mailing lists.
+
+
+Tools you Need and Their Environment
+------------------------------------
+
+You need some tools to be able to build Erlang/OTP on Windows. Most
+notably you'll need Cygwin, MSYS or MSYS2, Visual Studio and Microsofts 
+Windows SDK, but you might also want a Java compiler, the NSIS install 
+system and OpenSSL. Well, here's some information about the different 
+tools:
+
+*   Cygwin, the very latest is usually best. Get all the development
+    tools and of course all the basic ditto. Make sure to get jar and 
+    also make sure *not* to install a Cygwin'ish Java, since the Cygwin 
+    jar command is used but Sun's Java compiler and virtual machine.
+
+    If you are going to build a 64bit Windows version, you should make
+    sure to get MinGW's 64bit gcc installed with Cygwin. It's in one of
+    the development packages.
+
+    URL: <http://www.cygwin.com>
+
+    Get the installer from the website and use it to install
+    Cygwin. Be sure to have fair privileges. If you're on an NT domain you
+    should consider running `mkpasswd -d` and `mkgroup -d` after the
+    installation to get the user databases correct. See their respective
+    manual pages.
+
+    When you start your first bash shell, you will get an awful prompt. You
+    might also have a `PATH` environment variable that contains backslashes
+    and such. Edit `$HOME/.profile` and `$HOME/.bashrc` to set fair prompts
+    and a correct PATH. Also do an `export SHELL` in `.profile`. For some
+    non-obvious reason the environment variable `$SHELL` is not exported in
+    bash. Also note that `.profile` is run at login time and `.bashrc` when
+    sub shells are created. You'll need to explicitly source `.bashrc` from
+    `.profile` if you want the commands there to be run at login time (like
+    setting up aliases, shell functions and the like). You can for example 
+    do like this at the end of `.profile`:
+
+        ENV=$HOME/.bashrc
+        export ENV
+        . $ENV
+
+    You might also want to setup X-windows (XFree86). That might be as easy 
+    as running startx from the command prompt and it might be much harder. 
+    Use Google to find help.
+
+    If you don't use X-windows, you might want to setup the Windows
+    console window by selecting properties in the console system menu
+    (upper left corner of the window, the Cygwin icon in the title
+    bar). Especially setting a larger screen buffer size (lines) is useful
+    as it gets you a scrollbar so you can see whatever error messages
+    that might appear.
+
+    There are a few other shells available, but in all examples below we assume
+    that you use bash.
+
+*   Alternatively you download MinGW and MSYS. You'll find the latest
+    installer at:
+
+    URL: <http://sourceforge.net/projects/mingw/files/Installer/mingw-get-inst/>
+
+    Make sure to install the basic dev tools, but avoid the MinGW autoconf and
+    install the msys one instead.  
+
+    To be able to build the 64bit VM, you will also need the 64bit
+    MinGW compiler from:
+
+    URL: <http://sourceforge.net/projects/mingw-w64/files/latest/download?source=files>
+
+    We've tried up to 1.0, but the latest version should do. Make sure you 
+    download the `mingw-w64-bin_i686-mingw_<something>.zip`, not a linux
+    version. You unzip the package on top of your MinGW installation
+    (`c:\MinGW`) and that's it.
+
+*   A third alternative is to download and install MSYS2 from:
+
+    URL: <https://msys2.github.io/>
+
+    When you've followed the instructions there, you also need to install 
+    these packages: autoconf, make, perl, and tar. You do so by running 
+    the following in the msys console:
+
+        pacman -S msys/autoconf msys/make msys/perl msys/tar 
+
+    You also need a gcc. If you installed the 64 bit MSYS2 you run:
+
+        mingw64/mingw-w64-x86_64-gcc
+
+    And for 32 bit MSYS2:
+
+        pacman -S mingw32/mingw-w64-i686-gcc
+        pacman -S mingw-w64-i686-editrights
+
+*   Visual Studio 2013 (Visual Studio 12.0). Download and run the web 
+    installer from: 
+
+        https://www.visualstudio.com/
+
+*   Microsofts Windows SDK version 8.1 (corresponding to VC++ 12.0 and
+    Visual Studio 2013). You'll find it here:
+    
+    URL: <https://msdn.microsoft.com/en-us/windows/desktop/bg162891.aspx>
+
+*   To help setup the environment, there is a bat file, 
+    `%PROGRAMFILES%\Mirosoft Visual Studio 12.0\VC\vcvarsall.bat`, 
+    that set's the appropriate
+    environment for a Windows command prompt. This is not appropriate
+    for bash, so you'll need to convert it to bash-style environments
+    by editing your `.bash_profile`. In my case, where the SDK is
+    installed in the default directory and `%PROGRAMFILES%` is
+    `C:\Program Files`, the commands for setting up a 32bit build
+    environment (on a 64bit or 32bit machine) look like this (in Cygwin):
+
+        # Some common paths
+        C_DRV=/cygdrive/c
+        PRG_FLS=$C_DRV/Program\ Files
+
+        # nsis
+        NSIS_BIN=$PRG_FLS/NSIS
+        # java
+        JAVA_BIN=$PROGRAMFILES/Java/jdk1.7.0_02/bin
+
+        ##
+        ## MS SDK
+        ##
+
+        CYGWIN=nowinsymlinks 
+
+        VISUAL_STUDIO_ROOT=$PRG_FLS/Microsoft\ Visual\ Studio\ 12.0
+        WIN_VISUAL_STUDIO_ROOT="C:\\Program Files\\Microsoft Visual Studio 12.0"
+        SDK=$PRG_FLS/Windows\ Kits/8.1
+        WIN_SDK="C:\\Program Files\\Windows Kits\\8.1"
+
+        PATH="$NSIS_BIN:\
+        $VISUAL_STUDIO_ROOT/VC/bin:\
+        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
+        $VISUAL_STUDIO_ROOT/Common7/IDE:\
+        $VISUAL_STUDIO_ROOT/Common7/Tools:\
+        $SDK/bin/x86
+        /usr/local/bin:/usr/bin:/bin:\
+        /cygdrive/c/WINDOWS/system32:/cygdrive/c/WINDOWS:\
+        /cygdrive/c/WINDOWS/system32/Wbem:\
+        $JAVA_BIN"
+
+        LIBPATH="$WIN_VISUAL_STUDIO_ROOT\\VC\\lib"
+
+        LIB="$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\;$WIN_SDK\\lib\\winv6.3\\um\\x86"
+
+        INCLUDE="$WIN_VISUAL_STUDIO_ROOT\\VC\\include\\;$WIN_SDK\\include\\shared\\;\
+        $WIN_SDK\\include\\um;$WIN_SDK\\include\\winrt\\;$WIN_SDK\\include\\um\\gl"
+
+        export CYGWIN PATH LIBPATH LIB INCLUDE
+
+    If you're using MinGW's MSYS instead, you need to change the `C_DRV` setting, 
+    which would read:
+
+        C_DRV=/c
+
+    and you also need to change the PATH environment variable to: 
+
+        MINGW_BIN=/c/MinGW/bin
+
+
+        PATH="$NSIS_BIN:\
+        $VISUAL_STUDIO_ROOT/VC/bin:\
+        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
+        $VISUAL_STUDIO_ROOT/Common7/IDE:\
+        $VISUAL_STUDIO_ROOT/Common7/Tools:\
+        $SDK/bin/x86:/usr/local/bin:\
+        $MINGW_BIN:\
+        /bin:/c/Windows/system32:/c/Windows:\
+        /c/Windows/System32/Wbem:\
+        $JAVA_BIN"
+
+    For MSYS2 you use the same `C_DRV` and PATH as for MSYS, only update the `MINGW_BIN`:
+
+        MINGW_BIN=/mingw32/bin
+ 
+
+    If you are building a 64 bit version of Erlang, you should set up 
+    PATHs etc a little differently. We have two templates to make things 
+    work in both Cygwin and MSYS but needs editing to work with MSYS2 (see the 
+    comments in the script). 
+    The following one is for 32 bits:
+ 
+        make_winpath()
+        { 
+            P=$1
+            if [ "$IN_CYGWIN" = "true" ]; then
+                cygpath -d "$P"
+            else
+                (cd "$P" && /bin/cmd //C "for %i in (".") do @echo %~fsi")
+            fi
+        }
+
+        make_upath()
+        {
+            P=$1
+            if [ "$IN_CYGWIN" = "true" ]; then
+                cygpath "$P"
+            else
+                echo "$P" | /bin/sed 's,^\([a-zA-Z]\):\\,/\L\1/,;s,\\,/,g'
+            fi
+        }
+
+        # Some common paths
+        if [ -x /usr/bin/msys-?.0.dll ]; then
+          # Without this the path conversion won't work
+          COMSPEC='C:\Windows\System32\cmd.exe'
+          MSYSTEM=MINGW32  # Comment out this line if in MSYS2
+          export MSYSTEM COMSPEC
+          # For MSYS2: Change /mingw/bin to the msys bin dir on the line below
+          PATH=/usr/local/bin:/mingw/bin:/bin:/c/Windows/system32:\
+          /c/Windows:/c/Windows/System32/Wbem
+          C_DRV=/c
+          IN_CYGWIN=false
+        else
+          PATH=/ldisk/overrides:/usr/local/bin:/usr/bin:/bin:\
+          /usr/X11R6/bin:/cygdrive/c/windows/system32:\
+          /cygdrive/c/windows:/cygdrive/c/windows/system32/Wbem
+          C_DRV=/cygdrive/c
+          IN_CYGWIN=true
+        fi
+
+        obe_otp_gcc_vsn_map="
+            .*=>default 
+        "   
+        obe_otp_64_gcc_vsn_map="
+            .*=>default
+        "
+        # Program Files 
+        PRG_FLS=$C_DRV/Program\ Files
+
+        # Visual Studio
+        VISUAL_STUDIO_ROOT=$PRG_FLS/Microsoft\ Visual\ Studio\ 12.0
+        WIN_VISUAL_STUDIO_ROOT="C:\\Program Files\\Microsoft Visual Studio 12.0"
+
+        # SDK
+        SDK=$PRG_FLS/Windows\ Kits/8.1
+        WIN_SDK="C:\\Program Files\\Windows Kits\\8.1"
+
+        # NSIS
+        NSIS_BIN=$PROGRAMFILES/NSIS
+
+        # Java 
+        JAVA_BIN=$PROGRAMFILES/Java/jdk1.7.0_02/bin
+
+        ## The PATH variable should be Cygwin'ish
+        VCPATH=
+        $VISUAL_STUDIO_ROOT/VC/bin:\
+        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
+        $VISUAL_STUDIO_ROOT/Common7/IDE:\
+        $VISUAL_STUDIO_ROOT/Common7/Tools:\
+        $SDK/bin/x86
+
+        ## Microsoft SDK libs
+        LIBPATH=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib
+
+        LIB=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\;$WIN_KITS\\lib\\winv6.3\\um\\x86
+
+        INCLUDE=$WIN_VISUAL_STUDIO_ROOT\\VC\\include\\;\
+        $WIN_KITS\\include\\shared\\;$WIN_KITS\\include\\um;\
+        $WIN_KITS\\include\\winrt\\;$WIN_KITS\\include\\um\\gl
+
+        # Put nsis, c compiler and java in path
+        export PATH=$VCPATH:$PATH:$JAVA_BIN:$NSIS_BIN
+
+        # Make sure LIB and INCLUDE is available for others
+        export LIBPATH LIB INCLUDE
+
+
+
+    The first part of the 64 bit template is identical to the 32 bit one, 
+    but there are some environment variable differences: 
+
+        # Program Files
+        PRG_FLS64=$C_DRV/Program\ Files
+        PRG_FLS32=$C_DRV/Program\ Files\ \(x86\)
+
+        # Visual Studio
+        VISUAL_STUDIO_ROOT=$PRG_FLS32/Microsoft\ Visual\ Studio\ 12.0
+        WIN_VISUAL_STUDIO_ROOT="C:\\Program Files (x86)\\Microsoft Visual Studio 12.0"
+
+        # SDK
+        SDK=$PRG_FLS32/Windows\ Kits/8.1
+        WIN_SDK="C:\\Program Files (x86)\\Windows Kits\\8.1"
+
+        # NSIS
+        NSIS_BIN=$PROGRAMFILES/NSIS
+        # Java 
+        JAVA_BIN=$PROGRAMFILES/Java/jdk1.7.0_02/bin
+
+        ## The PATH variable should be Cygwin'ish
+        VCPATH=
+        $VISUAL_STUDIO_ROOT/VC/bin/amd64:\
+        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
+        $VISUAL_STUDIO_ROOT/Common7/IDE:\
+        $VISUAL_STUDIO_ROOT/Common7/Tools:\
+        $SDK/bin/x86
+
+        ## Microsoft SDK libs
+        LIBPATH=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\amd64
+
+        LIB=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\amd64\\;\
+        $WIN_KITS\\lib\\winv6.3\\um\\x64
+
+        INCLUDE=$WIN_VISUAL_STUDIO_ROOT\\VC\\include\\;\
+        $WIN_KITS\\include\\shared\\;$WIN_KITS\\include\\um;\
+        $WIN_KITS\\include\\winrt\\;$WIN_KITS\\include\\um\\gl
+
+        # Put nsis, c compiler and java in path
+        export PATH=$VCPATH:$PATH:$JAVA_BIN:$NSIS_BIN
+
+        # Make sure LIB and INCLUDE is available for others
+        export LIBPATH LIB INCLUDE
+
+
+    Make sure to set the PATH so that NSIS and Microsoft SDK is found 
+    before the MSYS/Cygwin tools and that Java is last in the PATH.
+
+    Make a simple hello world and try to compile it with the `cl` 
+    command from within bash. If that does not work, your environment 
+    needs fixing. Remember, there should be
+    no backslashes in your path environment variable in Cygwin bash,
+    but LIB and INCLUDE should contain Windows style paths with
+    semicolon, drive letters and backslashes.
+
+*   Sun's Java JDK 1.6.0 or later. Our Java code (jinterface, ic) is
+    written for JDK 1.6.0. Get it for Windows and install it, the JRE is
+    not enough. If you don't care about Java, you can skip this step. The
+    result will be that jinterface is not built.
+
+    URL: <http://java.sun.com>
+
+    Add javac *LAST* to your path environment in bash, in my case this means:
+
+        `PATH="$PATH:/cygdrive/c/Program Files/Java/jdk1.7.0_02/bin"`
+
+    No `CLASSPATH` or anything is needed. Type `javac` in the bash prompt
+    and you should get a list of available Java options. Make sure, e.g by
+    typing `type java`, that you use the Java you installed. Note however that
+    Cygwin's/MinGW's/MSYS2's `jar.exe` is used. That's why the JDK bin-directory should be
+    added last in the `PATH`.
+
+*   Nullsoft NSIS installer system. You need this to build the self
+    installing package. It's a free open source installer that's much
+    nicer to use than the commercial Wise and Install shield
+    installers. This is the installer we use for commercial releases as
+    well.
+
+    URL: <http://nsis.sourceforge.net/download>
+
+    Install the lot, especially the modern user interface components, as
+    it's definitely needed. Put `makensis` in your path, in my case:
+
+        PATH=/cygdrive/c/Program\ Files/NSIS:$PATH
+
+    Type makensis at the bash prompt and you should get a list of options
+    if everything is OK.
+
+*   OpenSSL. This is if you want the SSL and crypto applications to
+    compile (and run). There are prebuilt binaries, which you can just 
+    download and install, available here:
+
+    URL: <http://openssl.org/community/binaries.html>
+
+    We would recommend using 1.0.2d. 
+
+*   Building with wxWidgets. Download wxWidgets-3.0.3 or higher.
+
+    Install or unpack it to the pgm folder:
+    Cygwin: 
+        `DRIVE:/PATH/cygwin/opt/local/pgm`
+    MSYS:
+        `DRIVE:/PATH/MinGW/msys/1.0/opt/local/pgm`
+    MSYS2:
+        `DRIVE:/PATH/msys<32/64>/opt/local/pgm`
+
+    If the `wxUSE_POSTSCRIPT` isn't enabled in  `<path\to\pgm>\wxMSW-3.0.3\include\wx\msw\setup.h`,
+    enable it.
+
+    build: From a command prompt with the VC tools available (See the
+    instructions for OpenSSL build above for help on starting the
+    proper command prompt in RELEASE mode):
+	   
+        C:\...\> cd <path\to\pgm>\wxMSW-3.0.3\build\msw
+        C:\...\> nmake BUILD=release SHARED=0 DIR_SUFFIX_CPU= -f makefile.vc
+    
+    Or - if building a 64bit version:
+
+        C:\...\> cd <path\to\pgm>\wxMSW-3.0.3\build\msw
+        C:\...\> nmake TARGET_CPU=amd64 BUILD=release SHARED=0 DIR_SUFFIX_CPU= -f makefile.vc
+    	   
+*   Get the Erlang source distribution (from <http://www.erlang.org/download.html>).
+    The same as for Unix platforms. Preferably use tar from within Cygwin, MSYS or MSYS2 to
+    unpack the source tar.gz (`tar zxf otp_src_%OTP-REL%.tar.gz`).
+
+    Set the environment `ERL_TOP` to point to the root directory of the
+    source distribution. Let's say I stood in `$HOME/src` and unpacked
+    `otp_src_%OTP-REL%.tar.gz`, I then add the following to `.profile`:
+
+        ERL_TOP=$HOME/src/otp_src_%OTP-REL%
+        export $ERL_TOP
+
+
+The Shell Environment
+---------------------
+
+So, if you have followed the instructions above, when you start a bash
+shell, you should have an INCLUDE environment with a Windows style
+path, a LIB environment variable also in Windows style, and finally a
+PATH that let's you reach cl, makensis, javac etc from the
+command prompt (use `which cl` etc to verify from bash).
+
+You should also have an `ERL_TOP` environment variable that is *Cygwin
+style*, and points to a directory containing, among other files, the
+script `otp_build`.
+
+A final massage of the environment is needed, and that is done by
+the script `$ERL_TOP/otp_build`. Start bash and do the following, note
+the "back-ticks" (\`), can be quite hard to get on some keyboards, but
+pressing the back-tick key followed by the space bar might do it...
+
+    $ cd $ERL_TOP
+    $ eval `./otp_build env_win32`
+
+If you're unable to produce back-ticks on your keyboard, you can use
+the ksh variant:
+
+    $ cd $ERL_TOP
+    $ eval $(./otp_build env_win32)
+
+If you are building a 64 bit version, you supply `otp_build` with an architecture parameter:
+
+    $ cd $ERL_TOP
+    $ eval `./otp_build env_win32 x64`
+     
+
+This should do the final touch to the environment and building should
+be easy after this. You could run `./otp_build env_win32` without
+`eval` just to see what it does, and to see that the environment it
+sets seems OK. The path is cleaned of spaces if possible (using DOS
+style short names instead), the variables `OVERRIDE_TARGET`, `CC`, `CXX`,
+`AR` and `RANLIB` are set to their respective wrappers and the directories
+`$ERL_TOP/erts/etc/win32/<cygwin/msys>_tools/vc` and
+`$ERL_TOP/erts/etc/win32/<cygwin/msys>_tool` are added first in the PATH.
+
+Now you can check which erlc you have by writing `type erlc` in your shell. 
+It should reside in `$ERL_TOP/erts/etc/win32/cygwin_tools`
+or `$ERL_TOP/erts/etc/win32/msys_tools`.
+
+
+Building and Installing
+-----------------------
+
+Building is easiest using the `otp_build` script: 
+
+    $ ./otp_build autoconf # Ignore the warning blob about versions of autoconf
+    $ ./otp_build configure <optional configure options>
+    $ ./otp_build boot -a
+    $ ./otp_build release -a <installation directory>
+    $ ./otp_build installer_win32 <installation directory> # optional
+
+Now you will have a file called `otp_win32_%OTP-REL%.exe` or `otp_win64_%OTP-REL%.exe` 
+in the `<installation directory>`, i.e. `$ERL_TOP/release/win32`.
+
+Lets get into more detail:
+
+1.  `$ ./otp_build autoconf` - This step rebuilds the configure scripts
+    to work correctly in your environment. In an ideal world, this
+    would not be needed, but alas, we have encountered several
+    incompatibilities between our distributed configure scripts (generated
+    on a Linux platform) and the Cygwin/MSYS/MSYS2 environment over the
+    years. Running autoconf in Cygwin/MSYS/MSYS2 ensures that the configure 
+    scripts are generated in a compatible way and that they will work well
+    in the next step.
+
+2.  `$ ./otp_build configure` - This runs the newly generated configure
+    scripts with options making configure behave nicely. The target machine
+    type is plainly `win32`, so a lot of the configure-scripts recognize
+    this awkward target name and behave accordingly. The CC variable also
+    makes the compiler be `cc.sh`, which wraps MSVC++, so all configure
+    tests regarding the C compiler gets to run the right compiler. A lot of
+    the tests are not needed on Windows, but we thought it best to run the
+    whole configure anyway.
+
+3.  `$ ./otp_build boot -a` - This uses the bootstrap directory (shipped
+    with the source, `$ERL_TOP/bootstrap`) to build a complete OTP
+    system. When this is done you can run erl from within the source tree; 
+    just type `$ERL_TOP/bin/erl` and you whould have the prompt. 
+
+4.  `$ ./otp_build release -a` - Builds a commercial release tree from the
+    source tree. The default is to put it in `$ERL_TOP/release/win32`. You can
+    give any directory as parameter (Cygwin style), but it doesn't really
+    matter if you're going to build a self extracting installer too. 
+
+5.  `$ ./otp_build installer_win32` - Creates the self extracting installer executable. 
+    The executable `otp_win32_%OTP-REL%.exe` or `otp_win64_%OTP-REL%.exe` will be placed
+    in the top directory of the release created in the previous step. If
+    no release directory is specified, the release is expected to have
+    been built to `$ERL_TOP/release/win32`, which also will be the place
+    where the installer executable will be placed. If you specified some
+    other directory for the release (i.e. `./otp_build release -a
+    /tmp/erl_release`), you're expected to give the same parameter here,
+    (i.e. `./otp_build installer_win32 /tmp/erl_release`). You need to have
+    a full NSIS installation and `makensis.exe` in your path for this to
+    work. Once you have created the installer, you can run it to
+    install Erlang/OTP in the regular way, just run the executable and
+    follow the steps in the installation wizard. To get all default settings
+    in the installation without any questions asked, you run the executable
+    with the parameter `/S` (capital S) like in:
+
+        $ cd $ERL_TOP
+        $ release/win32/otp_win32_%OTP-REL% /S
+        ...
+
+    or
+
+        $ cd $ERL_TOP
+        $ release/win32/otp_win64_%OTP-REL% /S
+        ...
+    
+
+    and after a while Erlang/OTP-%OTP-REL% will have been installed in
+    `C:\Program Files\erl%ERTS-VSN%\`, with shortcuts in the menu etc.
+
+
+Development
+-----------
+
+Once the system is built, you might want to change it. Having a test
+release in some nice directory might be useful, but you can also run
+Erlang from within the source tree. The target `local_setup`, makes
+the program `$ERL_TOP/bin/erl.exe` usable and it also uses all the OTP
+libraries in the source tree.
+
+If you hack the emulator, you can build the emulator executable
+by standing in `$ERL_TOP/erts/emulator` and do a simple
+
+    $ make opt
+
+Note that you need to have run ``(cd $ERL_TOP && eval `./otp_build env_win32`)``
+in the particular shell before building anything on Windows. After
+doing a make opt you can test your result by running `$ERL_TOP/bin/erl`.
+If you want to copy the result to a release directory (say
+`/tmp/erl_release`), you do this (still in  `$ERL_TOP/erts/emulator`)
+
+    $ make TESTROOT=/tmp/erl_release release
+
+That will copy the emulator executables.
+
+To make a debug build of the emulator, you need to recompile both
+`beam.dll` (the actual runtime system) and `erlexec.dll`. Do like this
+
+    $ cd $ERL_TOP
+    $ rm bin/win32/erlexec.dll
+    $ cd erts/emulator
+    $ make debug
+    $ cd ../etc
+    $ make debug
+
+and sometimes
+
+    $ cd $ERL_TOP
+    $ make local_setup
+
+So now when you run `$ERL_TOP/erl.exe`, you should have a debug compiled
+emulator, which you will see if you do a:
+
+    1> erlang:system_info(system_version).
+
+in the erlang shell. If the returned string contains `[debug]`, you
+got a debug compiled emulator.
+
+To hack the erlang libraries, you simply do a `make opt` in the
+specific "applications" directory, like:
+
+    $ cd $ERL_TOP/lib/stdlib
+    $ make opt
+
+or even in the source directory...
+
+    $ cd $ERL_TOP/lib/stdlib/src
+    $ make opt
+
+Note that you're expected to have a fresh Erlang in your path when
+doing this, preferably the plain %OTP-REL% you have built in the previous
+steps. You could also add `$ERL_TOP/bootstrap/bin` to your `PATH` before
+rebuilding specific libraries. That would give you a good enough
+Erlang system to compile any OTP erlang code.  Setting up the path
+correctly is a little bit tricky. You still need to have
+`$ERL_TOP/erts/etc/win32/cygwin_tools/vc` and
+`$ERL_TOP/erts/etc/win32/cygwin_tools` *before* the actual emulator
+in the path. A typical setting of the path for using the bootstrap
+compiler would be:
+
+    $ export PATH=$ERL_TOP/erts/etc/win32/cygwin_tools/vc\
+    :$ERL_TOP/erts/etc/win32/cygwin_tools:$ERL_TOP/bootstrap/bin:$PATH
+
+That should make it possible to rebuild any library without hassle...
+
+If you want to copy a library (an application) newly built, to a
+release area, you do like with the emulator:
+
+    $ cd $ERL_TOP/lib/stdlib
+    $ make TESTROOT=/tmp/erlang_release release
+
+Remember that:
+
+*   Windows specific C-code goes in the `$ERL_TOP/erts/emulator/sys/win32`,
+    `$ERL_TOP/erts/emulator/drivers/win32` or `$ERL_TOP/erts/etc/win32`.
+
+*   Windows specific erlang code should be used conditionally and the
+    host OS tested in *runtime*, the exactly same beam files should be
+    distributed for every platform! So write code like:
+
+        case os:type() of
+            {win32,_} ->
+                do_windows_specific();
+            Other ->
+                do_fallback_or_exit()
+        end,
+
+That's basically all you need to get going.
+
+
+Using GIT
+---------
+
+You might want to check out versions of the source code from GitHUB. That is possible directly in Cygwin, but not in MSYS. There is a project MsysGIT:
+
+URL:<http://code.google.com/p/msysgit/>
+
+that makes a nice Git port. The msys prompt you get from MsysGIT is
+however not compatible with the full version from MinGW, so you will
+need to check out files using MsysGIT's command prompt and then switch
+to a common MSYS command prompt for building. Also all test suites
+cannot be built as MsysGIT/MSYS does not handle symbolic links. 
+
+
+   [1]: http://www.erlang.org/static/doc/mailinglist.html
+   [2]: http://bugs.erlang.org
+   [3]: https://github.com/erlang/otp
+
+   [?TOC]: true
diff --git a/HOWTO/INSTALL-WIN32.md b/HOWTO/INSTALL-WIN32.md
index 98c608060d..aeb5cfa1cb 100644
--- a/HOWTO/INSTALL-WIN32.md
+++ b/HOWTO/INSTALL-WIN32.md
@@ -4,40 +4,31 @@ How to Build Erlang/OTP on Windows
 Introduction
 ------------
 
-This section describes how to build the Erlang emulator and the OTP 
-libraries on Windows. Note that the Windows binary releases are still 
-a preferred alternative if one does not have Microsoft’s development 
-tools and/or don’t want to install Cygwin, MSYS or MSYS2.
-
-The instructions apply to versions of Windows supporting the Cygwin 
-emulated gnuish environment or the MSYS or MSYS2 ditto. We’ve built on 
-the following platforms: Windows 2012, Windows 7, Windows 8 and Windows 10. 
-It’s probably possible to build on older platforms too, but you might 
-not be able to install the appropriate Microsoft SDK, Visual Studio or 
-OpenSSL, in which case you will need to go back to earlier compilers etc.  
-
-The procedure described uses either Cygwin, MSYS or MSYS2 as a build 
-environment. You run the bash shell in Cygwin/MSYS/MSYS2 and use the gnu 
-make/configure/autoconf etc to do the build. The emulator C-source code 
-is, however, mostly compiled with Microsoft Visual C++™, producing a 
-native Windows binary. This is the same procedure as we use to build the 
-pre-built binaries. Why we use VC++ and not gcc is explained further in 
-the FAQ section. 
-
-If you are not familiar with Cygwin, MSYS, MSYS2 or a Unix environment, 
-you’ll probably need to read up a bit on how that works. There are plenty of 
-documentation about this online.
-
-These instructions apply for both 32-bit and 64-bit Windows. Note that even 
-if you build a 64-bit version of Erlang, most of the directories and files 
-involved are still named win32. Some occurances of the name win64 are 
-however present. The installation file for a 64-bit Windows version of 
-Erlang, for example, is `otp_win64_%OTP-REL%.exe`.
+This section describes how to build the Erlang emulator and the OTP
+libraries on Windows. Note that the Windows binary releases are still
+a preferred alternative if one does not have Microsoft’s development
+tools and/or don’t want to install WSL.
+
+The instructions apply to Windows 10 (v.1809 and later) supporting the
+WSL.1 (Windows Subsystem for Linux v.1) and using Ubuntu 18.04 release.
+
+The procedure described uses WSL as a build environment.  You run the
+bash shell in WSL and use the gnu make/configure/autoconf etc to do
+the build. The emulator C-source code is, however, mostly compiled
+with Microsoft Visual C++™, producing a native Windows binary. This is
+the same procedure as we use to build the pre-built binaries. Why we
+use VC++ and not gcc is explained further in the FAQ section.
+
+These instructions apply for both 32-bit and 64-bit Windows. Note that
+even if you build a 64-bit version of Erlang, most of the directories
+and files involved are still named win32. Some occurrences of the name
+win64 are however present. The installation file for a 64-bit Windows
+version of Erlang, for example, is `otp_win64_%OTP-REL%.exe`.
 
 If you feel comfortable with the environment and build
 system, and have all the necessary tools, you have a great opportunity
 to make the Erlang/OTP distribution for Windows better. Please submit
-any suggestions to our [JIRA] [2] and patches to our [git project] [3] to let
+any suggestions to our [JIRA] [1] and patches to our [git project] [2] to let
 them find their way into the next version of Erlang. If making changes
 to the build system (like makefiles etc) please bear in mind that the
 same makefiles are used on Unix/VxWorks, so that your changes
@@ -46,56 +37,44 @@ specific code resides in the `$ERL_TOP/erts/emulator/sys/win32` and
 `$ERL_TOP/erts/etc/win32` directories mostly. The
 `$ERL_TOP/erts/emulator/beam` directory is for common code.
 
-We've used this build procedure for a couple of
-releases, and it has worked fine for us. Still, there might be all
-sorts of troubles on different machines and with different
-setups. We'll try to give hints wherever we've encountered difficulties,
-but please share your experiences by using the [erlang-questions] [1]
-mailing list. We cannot, of course, help everyone with all
-their issues, so please try to solve such issues and submit
-solutions/workarounds.
-
-Lets go then! We’ll start with a short version of the setup procedure, 
-followed by some FAQ, and then we’ll go into more details of the setup. 
-
 
 Short Version
 -------------
 
-In the following sections, we've described as much as we could about the 
-installation of the tools needed. Once the tools are installed, building 
-is quite easy. We have also tried to make these instructions understandable 
-for people with limited Unix experience. Cygwin/MSYS/MSYS2 is a whole new 
-environment to some Windows users, why careful explanation of environment 
-variables etc seemed to be in place. 
+In the following sections, we've described as much as we could about
+the installation of the tools needed. Once the tools are installed,
+building is quite easy. We have also tried to make these instructions
+understandable for people with limited Unix experience. WSL is a whole
+new environment to some Windows users, why careful explanation of
+environment variables etc seemed to be in place.
 
 This is the short story though, for the experienced and impatient:
 
-    *   Get and install complete Cygwin (latest), complete MinGW with MSYS or 
-        complete MSYS2
+    *   Get and install complete WSL environment
 
-    *   Install Visual Studio 12.0 (2013)
+    *   Install Visual Studio 2019
 
-    *   Install Microsofts Windows SDK 8.1 
+    *   Get and install windows JDK-8
 
-    *   Get and install Sun's JDK 1.6.0 or later
+    *   Get and install windows NSIS 3.05 or later (3.05 tried and working)
 
-    *   Get and install NSIS 2.01 or later (up to 2.46 tried and working)
+    *   Get, build and install OpenSSL v1.1.1d or later (up to 1.1.1d
+        tried & working) with static libs.
 
-    *   Get, build and install OpenSSL 0.9.8r or later (up to 1.0.2d
+    *   Get, build and install wxWidgets-3.1.3 or later (up to 3.1.3
         tried & working) with static libs.
 
     *   Get the Erlang source distribution (from
-        <http://www.erlang.org/download.html>) and unpack with 
-        Cygwin's/MSYS's/MSYS2's `tar`.
+        <http://www.erlang.org/download.html>) and unpack with `tar`
+        to the windows disk for example to: /mnt/c/src/
 
-    *   Set `ERL_TOP` to where you unpacked the source distribution
+    *   Install mingw-gcc: `sudo apt install gcc-mingw-w64`
 
-    *   `$ cd $ERL_TOP`
+    *   `$ cd UNPACK_DIR`
 
     *   Modify PATH and other environment variables so that all these tools
         are runnable from a bash shell. Still standing in `$ERL_TOP`, issue
-        the following commands (for 32-bit Windows, remove the x64 from the 
+        the following commands (for 32-bit Windows, remove the x64 from the
         first row and change `otp_win64_%OTP-REL%` to `otp_win32_%OTP-REL%` on
         the last row):
 
@@ -111,576 +90,110 @@ This is the short story though, for the experienced and impatient:
     Windows shell.
 
 
-Frequently Asked Questions
---------------------------
-
-*   Q: So, now I can build Erlang using GCC on Windows?
-
-    A: No, unfortunately not. You'll need Microsoft's Visual C++
-    still. A Bourne-shell script (cc.sh) wraps the Visual C++ compiler
-    and runs it from within the Cygwin environment. All other tools
-    needed to build Erlang are free-ware/open source, but not the C
-    compiler. The Windows SDK is however enough to build Erlang, you
-    do not need to buy Visual C++, just download the SDK (SDK version
-    8.1 == Visual studio 2013).
-
-*   Q: Why haven't you got rid of VC++ then, you \*\*\*\*\*\*?
-
-    A: Well, partly because it's a good compiler - really! Actually it's
-    been possible in late R11-releases to build using mingw instead of
-    visual C++ (you might see the remnants of that in some scripts and
-    directories). Unfortunately the development of the SMP version for
-    Windows broke the mingw build and we chose to focus on the VC++ build
-    as the performance has been much better in the VC++ versions. The
-    mingw build will possibly be back, but as long as VC++ gives better
-    performance, the commercial build will be a VC++ one.
-
-*   Q: OK, you need VC++, but now you've started to demand a quite recent
-    (and expensive) version of Visual Studio. Why?
-
-    A: Well, it's not expensive, it's free (as in free beer). Just
-    download and install the latest Windows SDK from Microsoft and all
-    the tools you need are there. The included debugger (WinDbg) is
-    also quite usable. That's what I used when porting Erlang to 64bit
-    Windows. Another reason to use later Microsoft compilers is 
-    DLL compatibility. DLL's using a new version of the standard
-    library might not load if the VM is compiled with an old VC++
-    version. So we should aim to use the latest freely available SDK
-    and compiler.
-
-*   Q: Can/will I build a Cygwin binary with the procedure you describe?
-
-    A: No, the result will be a pure Windows binary, and as far as I know,
-    it's not possible to make a Cygwin binary yet. That is of course
-    something desirable, but there are still some problems with the
-    dynamic linking (dynamic Erlang driver loading) as well as the TCP/IP
-    emulation in Cygwin, which, I'm sure of, will improve, but still has
-    some problems. Fixing those problems might be easy or might be hard.
-    I suggest you try yourself and share your experience. No one would be
-    happier if a simple `./configure && make` would produce a fully fledged
-    Cygwin binary. 
-
-*   Q: Hah, I saw you, you used GCC even though you said you didn't!
-
-    A: OK, I admit, one of the files is compiled using Cygwin's or
-    MinGW's GCC and the resulting object code is then converted to MS
-    VC++ compatible coff using a small C hack. It's because that
-    particular file, `beam_emu.c` benefits immensely from being able
-    to use the GCC labels-as-values extension, which boosts emulator
-    performance by up to 50%. That does unfortunately not (yet) mean
-    that all of OTP could be compiled using GCC. That particular
-    source code does not do anything system specific and actually is
-    adopted to the fact that GCC is used to compile it on Windows.
-
-*   Q: So now there's a MS VC++ project file somewhere and I can build OTP
-    using the nifty VC++ GUI?
-
-    A: No, never. The hassle of keeping the project files up to date and
-    do all the steps that constitute an OTP build from within the VC++ GUI
-    is simply not worth it, maybe even impossible. A VC++ project
-    file for Erlang/OTP will never happen.
-
-*   Q: So how does it all work then?
-
-    A: Cygwin, MSYS or MSYS2 is the environment, which closely resembles the
-    environment found on any Unix machine. It's almost like you had a
-    virtual Unix machine inside Windows. Configure, given certain
-    parameters, then creates makefiles that are used by the
-    environment's gnu-make to built the system. Most of the actual
-    compilers etc are not, however, Cygwin/MSYS/MSYS2 tools, so we've written
-    a couple of wrappers (Bourne-shell scripts), which reside in
-    `$ERL_TOP/etc/win32/cygwin_tools` and
-    `$ERL_TOP/etc/win32/msys_tools`. They all do conversion of
-    parameters and switches common in the Unix environment to fit the
-    native Windows tools. Most notable is of course the paths, which
-    in Cygwin/MSYS/MSYS2 are Unix-like paths with "forward slashes" (/) and
-    no drive letters. The Cygwin specific command `cygpath` is used
-    for most of the path conversions in a Cygwin environment. Other
-    tools are used (when needed) in the corresponding MSYS and MSYS2
-    environment. Luckily most compilers accept forward slashes instead
-    of backslashes as path separators, but one still have to get the drive
-    letters etc right, though. The wrapper scripts are not general in
-    the sense that, for example, cc.sh would understand and translate
-    every possible gcc option and pass correct options to
-    cl.exe. The principle is that the scripts are powerful enough to
-    allow building of Erlang/OTP, no more, no less. They might need
-    extensions to cope with changes during the development of Erlang, and
-    that's one of the reasons we made them into shell-scripts and not
-    Perl-scripts. We believe they are easier to understand and change
-    that way.
-
-    In `$ERL_TOP`, there is a script called `otp_build`. That script handles
-    the hassle of giving all the right parameters to `configure`/`make` and
-    also helps you set up the correct environment variables to work with
-    the Erlang source under Cygwin/MSYS/MSYS2.
-
-*   Q: You use and need Cygwin, but then you haven't taken the time to
-    port Erlang to the Cygwin environment but instead focus on your
-    commercial release, is that really ethical?
-
-    A: No, not really, but see this as a step in the right direction. 
-
-*   Q: Can I build something that looks exactly as the commercial release?
-
-    A: Yes, we use the exact same build procedure.
-
-*   Q: Which version of Cygwin/MSYS/MSYS2 and other tools do you use then?
-
-    A: For Cygwin, MSYS and MSYS2 alike, we try to use the latest releases
-    available when building. What versions you use shouldn't really
-    matter. We try to include workarounds for the bugs we've found in
-    different Cygwin/MSYS/MSYS2 releases. Please help us add workarounds
-    for new Cygwin/MSYS/MSYS2-related bugs as soon as you encounter
-    them. Also please do submit bug reports to the appropriate Cygwin, MSYS
-    and/or MSYS2 developers. The GCC we used for %OTP-REL% was version
-    4.8.1 (MinGW 32bit) and 4.8.5 (MSYS2 64bit). We used  VC++ 12.0 
-    (i.e. Visual studio 2013), Sun's JDK 1.6.0\_45 (32bit) and Sun's
-    JDK 1.7.0\_1 (64bit), NSIS 2.46, and Win32 OpenSSL 1.0.2d. Please
-    read the next section for details on what you need.
-
-*   Q: Can you help me setup X in Cygwin/MSYS/MSYS2?
-
-    A: No, unfortunately we haven't got time to help with Cygwin/MSYS/MSYS2 
-    related user problems, please read related websites, newsgroups and
-    mailing lists.
-
-
 Tools you Need and Their Environment
 ------------------------------------
 
 You need some tools to be able to build Erlang/OTP on Windows. Most
-notably you'll need Cygwin, MSYS or MSYS2, Visual Studio and Microsofts 
-Windows SDK, but you might also want a Java compiler, the NSIS install 
-system and OpenSSL. Well, here's some information about the different 
-tools:
-
-*   Cygwin, the very latest is usually best. Get all the development
-    tools and of course all the basic ditto. Make sure to get jar and 
-    also make sure *not* to install a Cygwin'ish Java, since the Cygwin 
-    jar command is used but Sun's Java compiler and virtual machine.
-
-    If you are going to build a 64bit Windows version, you should make
-    sure to get MinGW's 64bit gcc installed with Cygwin. It's in one of
-    the development packages.
-
-    URL: <http://www.cygwin.com>
-
-    Get the installer from the website and use it to install
-    Cygwin. Be sure to have fair privileges. If you're on an NT domain you
-    should consider running `mkpasswd -d` and `mkgroup -d` after the
-    installation to get the user databases correct. See their respective
-    manual pages.
-
-    When you start your first bash shell, you will get an awful prompt. You
-    might also have a `PATH` environment variable that contains backslashes
-    and such. Edit `$HOME/.profile` and `$HOME/.bashrc` to set fair prompts
-    and a correct PATH. Also do an `export SHELL` in `.profile`. For some
-    non-obvious reason the environment variable `$SHELL` is not exported in
-    bash. Also note that `.profile` is run at login time and `.bashrc` when
-    sub shells are created. You'll need to explicitly source `.bashrc` from
-    `.profile` if you want the commands there to be run at login time (like
-    setting up aliases, shell functions and the like). You can for example 
-    do like this at the end of `.profile`:
-
-        ENV=$HOME/.bashrc
-        export ENV
-        . $ENV
-
-    You might also want to setup X-windows (XFree86). That might be as easy 
-    as running startx from the command prompt and it might be much harder. 
-    Use Google to find help.
-
-    If you don't use X-windows, you might want to setup the Windows
-    console window by selecting properties in the console system menu
-    (upper left corner of the window, the Cygwin icon in the title
-    bar). Especially setting a larger screen buffer size (lines) is useful
-    as it gets you a scrollbar so you can see whatever error messages
-    that might appear.
-
-    There are a few other shells available, but in all examples below we assume
-    that you use bash.
-
-*   Alternatively you download MinGW and MSYS. You'll find the latest
-    installer at:
-
-    URL: <http://sourceforge.net/projects/mingw/files/Installer/mingw-get-inst/>
-
-    Make sure to install the basic dev tools, but avoid the MinGW autoconf and
-    install the msys one instead.  
-
-    To be able to build the 64bit VM, you will also need the 64bit
-    MinGW compiler from:
-
-    URL: <http://sourceforge.net/projects/mingw-w64/files/latest/download?source=files>
-
-    We've tried up to 1.0, but the latest version should do. Make sure you 
-    download the `mingw-w64-bin_i686-mingw_<something>.zip`, not a linux
-    version. You unzip the package on top of your MinGW installation
-    (`c:\MinGW`) and that's it.
-
-*   A third alternative is to download and install MSYS2 from:
+notably you'll need WSL (with ubuntu), Visual Studio and
+Microsofts Windows SDK, but you might also want a Java compiler, the
+NSIS install system, OpenSSL and wxWidgets. Well, here's some information about
+the different tools:
 
-    URL: <https://msys2.github.io/>
+*   WSL: Install WSL and Ubuntu in Windows 10
+    <https://docs.microsoft.com/en-us/windows/wsl/install-win10>
 
-    When you've followed the instructions there, you also need to install 
-    these packages: autoconf, make, perl, and tar. You do so by running 
-    the following in the msys console:
+    We have used and tested with WSL-1, WSL-2 was not available and may
+    not be prefered when building Erlang/OTP since access to the windows
+    disk is (currently) slower WSL-2.
 
-        pacman -S msys/autoconf msys/make msys/perl msys/tar 
+*   Visual Studio 2019
+    Download and run the installer from:
+      <http://visualstudio.microsoft.com/downloads>
+    Install C++ and SDK packages to the default installation directory.
 
-    You also need a gcc. If you installed the 64 bit MSYS2 you run:
-
-        mingw64/mingw-w64-x86_64-gcc
-
-    And for 32 bit MSYS2:
-
-        pacman -S mingw32/mingw-w64-i686-gcc
-        pacman -S mingw-w64-i686-editrights
-
-*   Visual Studio 2013 (Visual Studio 12.0). Download and run the web 
-    installer from: 
-
-        https://www.visualstudio.com/
-
-*   Microsofts Windows SDK version 8.1 (corresponding to VC++ 12.0 and
-    Visual Studio 2013). You'll find it here:
-    
-    URL: <https://msdn.microsoft.com/en-us/windows/desktop/bg162891.aspx>
-
-*   To help setup the environment, there is a bat file, 
-    `%PROGRAMFILES%\Mirosoft Visual Studio 12.0\VC\vcvarsall.bat`, 
-    that set's the appropriate
-    environment for a Windows command prompt. This is not appropriate
-    for bash, so you'll need to convert it to bash-style environments
-    by editing your `.bash_profile`. In my case, where the SDK is
-    installed in the default directory and `%PROGRAMFILES%` is
-    `C:\Program Files`, the commands for setting up a 32bit build
-    environment (on a 64bit or 32bit machine) look like this (in Cygwin):
-
-        # Some common paths
-        C_DRV=/cygdrive/c
-        PRG_FLS=$C_DRV/Program\ Files
-
-        # nsis
-        NSIS_BIN=$PRG_FLS/NSIS
-        # java
-        JAVA_BIN=$PROGRAMFILES/Java/jdk1.7.0_02/bin
-
-        ##
-        ## MS SDK
-        ##
-
-        CYGWIN=nowinsymlinks 
-
-        VISUAL_STUDIO_ROOT=$PRG_FLS/Microsoft\ Visual\ Studio\ 12.0
-        WIN_VISUAL_STUDIO_ROOT="C:\\Program Files\\Microsoft Visual Studio 12.0"
-        SDK=$PRG_FLS/Windows\ Kits/8.1
-        WIN_SDK="C:\\Program Files\\Windows Kits\\8.1"
-
-        PATH="$NSIS_BIN:\
-        $VISUAL_STUDIO_ROOT/VC/bin:\
-        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
-        $VISUAL_STUDIO_ROOT/Common7/IDE:\
-        $VISUAL_STUDIO_ROOT/Common7/Tools:\
-        $SDK/bin/x86
-        /usr/local/bin:/usr/bin:/bin:\
-        /cygdrive/c/WINDOWS/system32:/cygdrive/c/WINDOWS:\
-        /cygdrive/c/WINDOWS/system32/Wbem:\
-        $JAVA_BIN"
-
-        LIBPATH="$WIN_VISUAL_STUDIO_ROOT\\VC\\lib"
-
-        LIB="$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\;$WIN_SDK\\lib\\winv6.3\\um\\x86"
-
-        INCLUDE="$WIN_VISUAL_STUDIO_ROOT\\VC\\include\\;$WIN_SDK\\include\\shared\\;\
-        $WIN_SDK\\include\\um;$WIN_SDK\\include\\winrt\\;$WIN_SDK\\include\\um\\gl"
-
-        export CYGWIN PATH LIBPATH LIB INCLUDE
-
-    If you're using MinGW's MSYS instead, you need to change the `C_DRV` setting, 
-    which would read:
-
-        C_DRV=/c
-
-    and you also need to change the PATH environment variable to: 
-
-        MINGW_BIN=/c/MinGW/bin
-
-
-        PATH="$NSIS_BIN:\
-        $VISUAL_STUDIO_ROOT/VC/bin:\
-        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
-        $VISUAL_STUDIO_ROOT/Common7/IDE:\
-        $VISUAL_STUDIO_ROOT/Common7/Tools:\
-        $SDK/bin/x86:/usr/local/bin:\
-        $MINGW_BIN:\
-        /bin:/c/Windows/system32:/c/Windows:\
-        /c/Windows/System32/Wbem:\
-        $JAVA_BIN"
-
-    For MSYS2 you use the same `C_DRV` and PATH as for MSYS, only update the `MINGW_BIN`:
-
-        MINGW_BIN=/mingw32/bin
- 
-
-    If you are building a 64 bit version of Erlang, you should set up 
-    PATHs etc a little differently. We have two templates to make things 
-    work in both Cygwin and MSYS but needs editing to work with MSYS2 (see the 
-    comments in the script). 
-    The following one is for 32 bits:
- 
-        make_winpath()
-        { 
-            P=$1
-            if [ "$IN_CYGWIN" = "true" ]; then
-                cygpath -d "$P"
-            else
-                (cd "$P" && /bin/cmd //C "for %i in (".") do @echo %~fsi")
-            fi
-        }
-
-        make_upath()
-        {
-            P=$1
-            if [ "$IN_CYGWIN" = "true" ]; then
-                cygpath "$P"
-            else
-                echo "$P" | /bin/sed 's,^\([a-zA-Z]\):\\,/\L\1/,;s,\\,/,g'
-            fi
-        }
-
-        # Some common paths
-        if [ -x /usr/bin/msys-?.0.dll ]; then
-          # Without this the path conversion won't work
-          COMSPEC='C:\Windows\System32\cmd.exe'
-          MSYSTEM=MINGW32  # Comment out this line if in MSYS2
-          export MSYSTEM COMSPEC
-          # For MSYS2: Change /mingw/bin to the msys bin dir on the line below
-          PATH=/usr/local/bin:/mingw/bin:/bin:/c/Windows/system32:\
-          /c/Windows:/c/Windows/System32/Wbem
-          C_DRV=/c
-          IN_CYGWIN=false
-        else
-          PATH=/ldisk/overrides:/usr/local/bin:/usr/bin:/bin:\
-          /usr/X11R6/bin:/cygdrive/c/windows/system32:\
-          /cygdrive/c/windows:/cygdrive/c/windows/system32/Wbem
-          C_DRV=/cygdrive/c
-          IN_CYGWIN=true
-        fi
-
-        obe_otp_gcc_vsn_map="
-            .*=>default 
-        "   
-        obe_otp_64_gcc_vsn_map="
-            .*=>default
-        "
-        # Program Files 
-        PRG_FLS=$C_DRV/Program\ Files
-
-        # Visual Studio
-        VISUAL_STUDIO_ROOT=$PRG_FLS/Microsoft\ Visual\ Studio\ 12.0
-        WIN_VISUAL_STUDIO_ROOT="C:\\Program Files\\Microsoft Visual Studio 12.0"
-
-        # SDK
-        SDK=$PRG_FLS/Windows\ Kits/8.1
-        WIN_SDK="C:\\Program Files\\Windows Kits\\8.1"
-
-        # NSIS
-        NSIS_BIN=$PROGRAMFILES/NSIS
-
-        # Java 
-        JAVA_BIN=$PROGRAMFILES/Java/jdk1.7.0_02/bin
-
-        ## The PATH variable should be Cygwin'ish
-        VCPATH=
-        $VISUAL_STUDIO_ROOT/VC/bin:\
-        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
-        $VISUAL_STUDIO_ROOT/Common7/IDE:\
-        $VISUAL_STUDIO_ROOT/Common7/Tools:\
-        $SDK/bin/x86
-
-        ## Microsoft SDK libs
-        LIBPATH=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib
-
-        LIB=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\;$WIN_KITS\\lib\\winv6.3\\um\\x86
-
-        INCLUDE=$WIN_VISUAL_STUDIO_ROOT\\VC\\include\\;\
-        $WIN_KITS\\include\\shared\\;$WIN_KITS\\include\\um;\
-        $WIN_KITS\\include\\winrt\\;$WIN_KITS\\include\\um\\gl
-
-        # Put nsis, c compiler and java in path
-        export PATH=$VCPATH:$PATH:$JAVA_BIN:$NSIS_BIN
-
-        # Make sure LIB and INCLUDE is available for others
-        export LIBPATH LIB INCLUDE
-
-
-
-    The first part of the 64 bit template is identical to the 32 bit one, 
-    but there are some environment variable differences: 
-
-        # Program Files
-        PRG_FLS64=$C_DRV/Program\ Files
-        PRG_FLS32=$C_DRV/Program\ Files\ \(x86\)
-
-        # Visual Studio
-        VISUAL_STUDIO_ROOT=$PRG_FLS32/Microsoft\ Visual\ Studio\ 12.0
-        WIN_VISUAL_STUDIO_ROOT="C:\\Program Files (x86)\\Microsoft Visual Studio 12.0"
-
-        # SDK
-        SDK=$PRG_FLS32/Windows\ Kits/8.1
-        WIN_SDK="C:\\Program Files (x86)\\Windows Kits\\8.1"
-
-        # NSIS
-        NSIS_BIN=$PROGRAMFILES/NSIS
-        # Java 
-        JAVA_BIN=$PROGRAMFILES/Java/jdk1.7.0_02/bin
-
-        ## The PATH variable should be Cygwin'ish
-        VCPATH=
-        $VISUAL_STUDIO_ROOT/VC/bin/amd64:\
-        $VISUAL_STUDIO_ROOT/VC/vcpackages:\
-        $VISUAL_STUDIO_ROOT/Common7/IDE:\
-        $VISUAL_STUDIO_ROOT/Common7/Tools:\
-        $SDK/bin/x86
-
-        ## Microsoft SDK libs
-        LIBPATH=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\amd64
-
-        LIB=$WIN_VISUAL_STUDIO_ROOT\\VC\\lib\\amd64\\;\
-        $WIN_KITS\\lib\\winv6.3\\um\\x64
-
-        INCLUDE=$WIN_VISUAL_STUDIO_ROOT\\VC\\include\\;\
-        $WIN_KITS\\include\\shared\\;$WIN_KITS\\include\\um;\
-        $WIN_KITS\\include\\winrt\\;$WIN_KITS\\include\\um\\gl
-
-        # Put nsis, c compiler and java in path
-        export PATH=$VCPATH:$PATH:$JAVA_BIN:$NSIS_BIN
-
-        # Make sure LIB and INCLUDE is available for others
-        export LIBPATH LIB INCLUDE
-
-
-    Make sure to set the PATH so that NSIS and Microsoft SDK is found 
-    before the MSYS/Cygwin tools and that Java is last in the PATH.
-
-    Make a simple hello world and try to compile it with the `cl` 
-    command from within bash. If that does not work, your environment 
-    needs fixing. Remember, there should be
-    no backslashes in your path environment variable in Cygwin bash,
-    but LIB and INCLUDE should contain Windows style paths with
-    semicolon, drive letters and backslashes.
-
-*   Sun's Java JDK 1.6.0 or later. Our Java code (jinterface, ic) is
-    written for JDK 1.6.0. Get it for Windows and install it, the JRE is
-    not enough. If you don't care about Java, you can skip this step. The
+*   Java JDK 8 or later  (optional)
+    If you don't care about Java, you can skip this step. The
     result will be that jinterface is not built.
 
-    URL: <http://java.sun.com>
+    Our Java code (jinterface, ic) is tested on windows with JDK 8.
+    Get it for Windows and install it, the JRE is not enough.
+
+    URL: <http://www.oracle.com/java/technologies/javase-downloads.html>
 
-    Add javac *LAST* to your path environment in bash, in my case this means:
+    Add javac to your path environment, in my case this means:
 
-        `PATH="$PATH:/cygdrive/c/Program Files/Java/jdk1.7.0_02/bin"`
+        `PATH="/mnt/c/Program\ Files/Java/jdk1.8.0_241/bin:$PATH`
 
-    No `CLASSPATH` or anything is needed. Type `javac` in the bash prompt
-    and you should get a list of available Java options. Make sure, e.g by
-    typing `type java`, that you use the Java you installed. Note however that
-    Cygwin's/MinGW's/MSYS2's `jar.exe` is used. That's why the JDK bin-directory should be
-    added last in the `PATH`.
+    No `CLASSPATH` or anything is needed. Type `javac.exe` in the bash prompt
+    and you should get a list of available Java options.
 
-*   Nullsoft NSIS installer system. You need this to build the self
-    installing package. It's a free open source installer that's much
-    nicer to use than the commercial Wise and Install shield
-    installers. This is the installer we use for commercial releases as
-    well.
+*   Nullsoft NSIS installer system (optional)
+    You need this to build the self installing package.
 
+    Download and run the installer from:
     URL: <http://nsis.sourceforge.net/download>
 
-    Install the lot, especially the modern user interface components, as
-    it's definitely needed. Put `makensis` in your path, in my case:
+    Add 'makensis.exe' to your path environment:
 
-        PATH=/cygdrive/c/Program\ Files/NSIS:$PATH
+         `PATH="/mnt/c/Program\ Files/NSIS/Bin:$PATH`
 
-    Type makensis at the bash prompt and you should get a list of options
-    if everything is OK.
+    Type `which makensis.exe` in the bash prompt and you should get the
+    path to the program.
 
-*   OpenSSL. This is if you want the SSL and crypto applications to
-    compile (and run). There are prebuilt binaries, which you can just 
-    download and install, available here:
+*   OpenSSL (optional)
+    You need this to build crypto, ssh and ssl libs.
 
-    URL: <http://openssl.org/community/binaries.html>
+    We recommend v1.1.1d or later.
+    There are prebuilt avaiable binaries, which you can just
+    download and install, available here:
+    URL: <http://wiki.openssl.org/index.php/Binaries>
 
-    We would recommend using 1.0.2d. 
+    Install into `C:/OpenSSL-Win64` (or `C:/OpenSSL-Win32`)
 
-*   Building with wxWidgets. Download wxWidgets-3.0.3 or higher.
+*   wxWidgets (optional)
+    You need this to build wx and use gui's in debugger and observer.
 
-    Install or unpack it to the pgm folder:
-    Cygwin: 
-        `DRIVE:/PATH/cygwin/opt/local/pgm`
-    MSYS:
-        `DRIVE:/PATH/MinGW/msys/1.0/opt/local/pgm`
-    MSYS2:
-        `DRIVE:/PATH/msys<32/64>/opt/local/pgm`
+    We recommend v3.1.3 or later.
+    Unpack into `c:/opt/local64/pgm/wxWidgets-3.1.3`
 
-    If the `wxUSE_POSTSCRIPT` isn't enabled in  `<path\to\pgm>\wxMSW-3.0.3\include\wx\msw\setup.h`,
+    If the `wxUSE_POSTSCRIPT` isn't enabled in  `c:/opt/local64/pgm/wxWidgets-3.1.3/include/wx/msw/setup.h`,
     enable it.
 
-    build: From a command prompt with the VC tools available (See the
-    instructions for OpenSSL build above for help on starting the
-    proper command prompt in RELEASE mode):
-	   
-        C:\...\> cd <path\to\pgm>\wxMSW-3.0.3\build\msw
-        C:\...\> nmake BUILD=release SHARED=0 DIR_SUFFIX_CPU= -f makefile.vc
-    
-    Or - if building a 64bit version:
+    Build with:
 
-        C:\...\> cd <path\to\pgm>\wxMSW-3.0.3\build\msw
+        C:\...\> cd c:\opt\local64\pgm\wxWidgets-3.1.3\build\msw
         C:\...\> nmake TARGET_CPU=amd64 BUILD=release SHARED=0 DIR_SUFFIX_CPU= -f makefile.vc
-    	   
+
+    Remove the `TARGET_CPU=amd64` for 32bit build.
+
 *   Get the Erlang source distribution (from <http://www.erlang.org/download.html>).
-    The same as for Unix platforms. Preferably use tar from within Cygwin, MSYS or MSYS2 to
-    unpack the source tar.gz (`tar zxf otp_src_%OTP-REL%.tar.gz`).
+    The same as for Unix platforms. Preferably use tar to
+    unpack the source tar.gz (`tar zxf otp_src_%OTP-REL%.tar.gz`) to somewhere
+    on the windows disk, `/mnt/c/path/to/otp_src`
+
+    NOTE: It is important that source on the windows disk.
 
     Set the environment `ERL_TOP` to point to the root directory of the
-    source distribution. Let's say I stood in `$HOME/src` and unpacked
+    source distribution. Let's say I stood in `/mnt/c/src` and unpacked
     `otp_src_%OTP-REL%.tar.gz`, I then add the following to `.profile`:
 
-        ERL_TOP=$HOME/src/otp_src_%OTP-REL%
-        export $ERL_TOP
+        ERL_TOP=/mnt/c/src/otp_src_%OTP-REL%
+        export ERL_TOP
+
 
 
 The Shell Environment
 ---------------------
 
-So, if you have followed the instructions above, when you start a bash
-shell, you should have an INCLUDE environment with a Windows style
-path, a LIB environment variable also in Windows style, and finally a
-PATH that let's you reach cl, makensis, javac etc from the
-command prompt (use `which cl` etc to verify from bash).
+The path variable should now contain the windows paths to javac.exe and makensis.exe.
 
-You should also have an `ERL_TOP` environment variable that is *Cygwin
-style*, and points to a directory containing, among other files, the
-script `otp_build`.
+Setup the environment with:
 
-A final massage of the environment is needed, and that is done by
-the script `$ERL_TOP/otp_build`. Start bash and do the following, note
-the "back-ticks" (\`), can be quite hard to get on some keyboards, but
-pressing the back-tick key followed by the space bar might do it...
-
-    $ cd $ERL_TOP
-    $ eval `./otp_build env_win32`
-
-If you're unable to produce back-ticks on your keyboard, you can use
-the ksh variant:
-
-    $ cd $ERL_TOP
-    $ eval $(./otp_build env_win32)
-
-If you are building a 64 bit version, you supply `otp_build` with an architecture parameter:
-
-    $ cd $ERL_TOP
+    $ export PATH
+    $ cd /mnt/c/path/to/otp_src/
     $ eval `./otp_build env_win32 x64`
-     
+
+This should setup the additional environment variables.
 
 This should do the final touch to the environment and building should
 be easy after this. You could run `./otp_build env_win32` without
@@ -688,18 +201,24 @@ be easy after this. You could run `./otp_build env_win32` without
 sets seems OK. The path is cleaned of spaces if possible (using DOS
 style short names instead), the variables `OVERRIDE_TARGET`, `CC`, `CXX`,
 `AR` and `RANLIB` are set to their respective wrappers and the directories
-`$ERL_TOP/erts/etc/win32/<cygwin/msys>_tools/vc` and
-`$ERL_TOP/erts/etc/win32/<cygwin/msys>_tool` are added first in the PATH.
+`$ERL_TOP/erts/etc/win32/wsl_tools/vc` and
+`$ERL_TOP/erts/etc/win32/wsl_tools` are added first in the PATH.
+
+Now you can check which erlc you have by writing `type erlc` in your shell.
+It should reside in `$ERL_TOP/erts/etc/win32/wsl_tools`.
+
+And running `cl.exe` should print the Microsoft compiler usage message.
 
-Now you can check which erlc you have by writing `type erlc` in your shell. 
-It should reside in `$ERL_TOP/erts/etc/win32/cygwin_tools`
-or `$ERL_TOP/erts/etc/win32/msys_tools`.
+The needed compiler environment variables are setup inside `otp_build`
+via `erts/etc/win32/wsl_tools/SetupWSLcross.bat`. It contains some
+hardcoded paths, if your installation path is different it can be added
+to that file.
 
 
 Building and Installing
 -----------------------
 
-Building is easiest using the `otp_build` script: 
+Building is easiest using the `otp_build` script:
 
     $ ./otp_build autoconf # Ignore the warning blob about versions of autoconf
     $ ./otp_build configure <optional configure options>
@@ -707,7 +226,7 @@ Building is easiest using the `otp_build` script:
     $ ./otp_build release -a <installation directory>
     $ ./otp_build installer_win32 <installation directory> # optional
 
-Now you will have a file called `otp_win32_%OTP-REL%.exe` or `otp_win64_%OTP-REL%.exe` 
+Now you will have a file called `otp_win32_%OTP-REL%.exe` or `otp_win64_%OTP-REL%.exe`
 in the `<installation directory>`, i.e. `$ERL_TOP/release/win32`.
 
 Lets get into more detail:
@@ -716,8 +235,8 @@ Lets get into more detail:
     to work correctly in your environment. In an ideal world, this
     would not be needed, but alas, we have encountered several
     incompatibilities between our distributed configure scripts (generated
-    on a Linux platform) and the Cygwin/MSYS/MSYS2 environment over the
-    years. Running autoconf in Cygwin/MSYS/MSYS2 ensures that the configure 
+    on a Linux platform) and the Cygwin/MSYS/MSYS2/WSL environment over the
+    years. Running autoconf in WSL ensures that the configure
     scripts are generated in a compatible way and that they will work well
     in the next step.
 
@@ -732,15 +251,15 @@ Lets get into more detail:
 
 3.  `$ ./otp_build boot -a` - This uses the bootstrap directory (shipped
     with the source, `$ERL_TOP/bootstrap`) to build a complete OTP
-    system. When this is done you can run erl from within the source tree; 
-    just type `$ERL_TOP/bin/erl` and you whould have the prompt. 
+    system. When this is done you can run erl from within the source tree;
+    just type `$ERL_TOP/bin/erl` and you should have the prompt.
 
 4.  `$ ./otp_build release -a` - Builds a commercial release tree from the
     source tree. The default is to put it in `$ERL_TOP/release/win32`. You can
-    give any directory as parameter (Cygwin style), but it doesn't really
-    matter if you're going to build a self extracting installer too. 
+    give any directory as parameter, but it doesn't really
+    matter if you're going to build a self extracting installer too.
 
-5.  `$ ./otp_build installer_win32` - Creates the self extracting installer executable. 
+5.  `$ ./otp_build installer_win32` - Creates the self extracting installer executable.
     The executable `otp_win32_%OTP-REL%.exe` or `otp_win64_%OTP-REL%.exe` will be placed
     in the top directory of the release created in the previous step. If
     no release directory is specified, the release is expected to have
@@ -765,7 +284,7 @@ Lets get into more detail:
         $ cd $ERL_TOP
         $ release/win32/otp_win64_%OTP-REL% /S
         ...
-    
+
 
     and after a while Erlang/OTP-%OTP-REL% will have been installed in
     `C:\Program Files\erl%ERTS-VSN%\`, with shortcuts in the menu etc.
@@ -835,13 +354,13 @@ steps. You could also add `$ERL_TOP/bootstrap/bin` to your `PATH` before
 rebuilding specific libraries. That would give you a good enough
 Erlang system to compile any OTP erlang code.  Setting up the path
 correctly is a little bit tricky. You still need to have
-`$ERL_TOP/erts/etc/win32/cygwin_tools/vc` and
-`$ERL_TOP/erts/etc/win32/cygwin_tools` *before* the actual emulator
+`$ERL_TOP/erts/etc/win32/wsl_tools/vc` and
+`$ERL_TOP/erts/etc/win32/wsl_tools` *before* the actual emulator
 in the path. A typical setting of the path for using the bootstrap
 compiler would be:
 
-    $ export PATH=$ERL_TOP/erts/etc/win32/cygwin_tools/vc\
-    :$ERL_TOP/erts/etc/win32/cygwin_tools:$ERL_TOP/bootstrap/bin:$PATH
+    $ export PATH=$ERL_TOP/erts/etc/win32/wsl_tools/vc\
+    :$ERL_TOP/erts/etc/win32/wsl_tools:$ERL_TOP/bootstrap/bin:$PATH
 
 That should make it possible to rebuild any library without hassle...
 
@@ -870,22 +389,106 @@ Remember that:
 That's basically all you need to get going.
 
 
-Using GIT
----------
 
-You might want to check out versions of the source code from GitHUB. That is possible directly in Cygwin, but not in MSYS. There is a project MsysGIT:
+Frequently Asked Questions
+--------------------------
+
+*   Q: So, now I can build Erlang using GCC on Windows?
+
+    A: No, unfortunately not. You'll need Microsoft's Visual C++
+    still. A Bourne-shell script (cc.sh) wraps the Visual C++ compiler
+    and runs it from within the WSL environment. All other tools
+    needed to build Erlang are free-ware/open source, but not the C
+    compiler.
+
+*   Q: Why haven't you got rid of VC++ then, you \*\*\*\*\*\*?
+
+    A: Well, partly because it's a good compiler - really! Actually it's
+    been possible in late R11-releases to build using mingw instead of
+    visual C++ (you might see the remnants of that in some scripts and
+    directories). Unfortunately the development of the SMP version for
+    Windows broke the mingw build and we chose to focus on the VC++ build
+    as the performance has been much better in the VC++ versions. The
+    mingw build will possibly be back, but as long as VC++ gives better
+    performance, the commercial build will be a VC++ one.
+
+*   Q: OK, you need VC++, but now you've started to demand a quite recent
+    (and expensive) version of Visual Studio. Why?
+
+    A: Well, it's not expensive, it's free (as in free beer). Just
+    download and install the latest Windows SDK from Microsoft and all
+    the tools you need are there. The included debugger (WinDbg) is
+    also quite usable. That's what I used when porting Erlang to 64bit
+    Windows. Another reason to use later Microsoft compilers is
+    DLL compatibility. DLL's using a new version of the standard
+    library might not load if the VM is compiled with an old VC++
+    version. So we should aim to use the latest freely available SDK
+    and compiler.
+
+*   Q: Hah, I saw you, you used GCC even though you said you didn't!
+
+    A: OK, I admit, one of the files is compiled using
+    MinGW's GCC and the resulting object code is then converted to MS
+    VC++ compatible coff using a small C hack. It's because that
+    particular file, `beam_emu.c` benefits immensely from being able
+    to use the GCC labels-as-values extension, which boosts emulator
+    performance by up to 50%. That does unfortunately not (yet) mean
+    that all of OTP could be compiled using GCC. That particular
+    source code does not do anything system specific and actually is
+    adopted to the fact that GCC is used to compile it on Windows.
+
+*   Q: So now there's a MS VC++ project file somewhere and I can build OTP
+    using the nifty VC++ GUI?
+
+    A: No, never. The hassle of keeping the project files up to date and
+    do all the steps that constitute an OTP build from within the VC++ GUI
+    is simply not worth it, maybe even impossible. A VC++ project
+    file for Erlang/OTP will never happen.
+
+*   Q: So how does it all work then?
+
+    A: WSL/Ubuntu is the environment, it's almost like you had a
+    virtual Unix machine inside Windows. Configure, given certain
+    parameters, then creates makefiles that are used by the
+    environment's gnu-make to built the system. Most of the actual
+    compilers etc are not, however, WSL tools, so we've written
+    a couple of wrappers (Bourne-shell scripts), which reside in
+    `$ERL_TOP/etc/win32/wsl_tools`. They all do conversion of
+    parameters and switches common in the Unix environment to fit the
+    native Windows tools. Most notable is of course the paths, which
+    in WSL are Unix-like paths with "forward slashes" (/) and
+    no drive letters. The WSL specific command `wslpath` is used
+    for most of the path conversions in a WSL environment.
+    Luckily most compilers accept forward slashes instead
+    of backslashes as path separators, but one still have to get the drive
+    letters etc right, though. The wrapper scripts are not general in
+    the sense that, for example, cc.sh would understand and translate
+    every possible gcc option and pass correct options to
+    cl.exe. The principle is that the scripts are powerful enough to
+    allow building of Erlang/OTP, no more, no less. They might need
+    extensions to cope with changes during the development of Erlang, and
+    that's one of the reasons we made them into shell-scripts and not
+    Perl-scripts. We believe they are easier to understand and change
+    that way.
+
+    In `$ERL_TOP`, there is a script called `otp_build`. That script handles
+    the hassle of giving all the right parameters to `configure`/`make` and
+    also helps you set up the correct environment variables to work with
+    the Erlang source under WSL.
+
+*   Q: Can I build something that looks exactly as the commercial release?
+
+    A: Yes, we use the exact same build procedure.
 
-URL:<http://code.google.com/p/msysgit/>
+*   Q: Which version of WSL and other tools do you use then?
 
-that makes a nice Git port. The msys prompt you get from MsysGIT is
-however not compatible with the full version from MinGW, so you will
-need to check out files using MsysGIT's command prompt and then switch
-to a common MSYS command prompt for building. Also all test suites
-cannot be built as MsysGIT/MSYS does not handle symbolic links. 
+    A:  We use WSL 1 with Ubuntu 18.04.
+    The GCC we used for %OTP-REL% was version 7.3-win32.
+    We used Visual studio 2019, Sun's JDK 1.8.0\_241,
+    NSIS 3.05, Win32 OpenSSL 1.1.1d and wxWidgets-3.1.3.
 
 
-   [1]: http://www.erlang.org/static/doc/mailinglist.html
-   [2]: http://bugs.erlang.org
-   [3]: https://github.com/erlang/otp
+   [1]: http://bugs.erlang.org
+   [2]: https://github.com/erlang/otp
 
    [?TOC]: true