Erlang -- How to Build Erlang/OTP on Windows

Installation Guide

User's Guide

Version 9.0

- User's Guide
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### Chapters

- Installing the Binary Release
  - Top of chapter
  - Windows
- Building and Installing Erlang/OTP
  - Top of chapter
  - Introduction
  - Required Utilities
  - Optional Utilities
  - How to Build and Install Erlang/OTP
  - Advanced configuration and build of Erlang/OTP
- Cross Compiling Erlang/OTP
  - Top of chapter
  - Introduction
  - Build and Install Procedure
  - Building and Installing the Documentation
  - Testing the cross compiled system
  - Currently Used Configuration Variables
- How to Build Erlang/OTP on Windows
  - Top of chapter
  - Introduction
  - Short Version
  - Frequently Asked Questions
  - Tools you Need and Their Environment
  - The Shell Environment
  - Building and Installing
  - Development
  - Using GIT
- Patching OTP Applications
  - Top of chapter
  - Introduction
  - Prerequisites
  - Using otp_patch_apply
  - Sanity check

# 4 How to Build Erlang/OTP on Windows

Table of Contents

- Introduction
- Short Version
- Frequently Asked Questions
- Tools you Need and Their Environment
- The Shell Environment
- Building and Installing
- Development
- Using GIT

### 4.1 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_20.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 and patches to our git project 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 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.

### 4.2 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_20 to otp_win32_20 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_20 /S

  Voila! Start->Programs->Erlang OTP 20->Erlang starts the Erlang Windows shell.

### 4.3 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 20 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.

### 4.4 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_20.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_20.tar.gz, I then add the following to .profile:

      ERL_TOP=$HOME/src/otp_src_20
      export $ERL_TOP

### 4.5 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.

### 4.6 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_20.exe or otp_win64_20.exe in the <installation directory>, i.e. $ERL_TOP/release/win32.

Lets get into more detail:

- $ ./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.

- $ ./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.

- $ ./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.

- $ ./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.

- $ ./otp_build installer_win32 - Creates the self extracting installer executable. The executable otp_win32_20.exe or otp_win64_20.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_20 /S
      ...

  or

      $ cd $ERL_TOP
      $ release/win32/otp_win64_20 /S
      ...

  and after a while Erlang/OTP-20 will have been installed in C:\Program Files\erl9.0\, with shortcuts in the menu etc.

### 4.7 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 20 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.

### 4.8 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.