README.cmake.md: Add new documentation for CMake buildsystem

While here, adapt and update some of the Windows-build
references in the other README files.

Change-Id: Id067774bde7511a736e156fc599b07837242336c
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230707150523.385264-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/search?l=mid&q=20230707150523.385264-1-frank@lichtenheld.com
Signed-off-by: Gert Doering <gert@greenie.muc.de>

1 files changed, 137 insertions, 0 deletions

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+OpenVPN Builds with CMake
+=========================
+
+For Windows builds we do not use the autotools-based buildsystem that we use
+for our Unix-like (Linux, BSDs, macOS, etc.) builds. Instead we added a
+separate (CMake)[https://cmake.org/]-based buildsystem.
+
+This buildsystem supports building for Windows both with MSVC (i.e. Visual
+Studio) and MinGW. MinGW builds are also supported as cross-compile
+from Linux.
+
+The official builds, which are also available as CMake presets (see
+`cmake --list-presets` and `CMakePresets.json`) all use
+(VCPKG)[https://github.com/microsoft/vcpkg/#vcpkg-overview] for dependency
+management. This allows us to do proper supply-chain management and
+also makes cross-building with MinGW on Linux much simpler. However,
+builds are also possible by providing the build dependencies manually,
+but that might require specifying more information to CMake.
+
+If you're looking to build the full Windows installer MSI, take a look
+at https://github.com/OpenVPN/openvpn-build.git .
+
+MSVC builds
+-----------
+
+The following tools are expected to be present on the system, you
+can them install with a package manager of your choice (e.g.
+chocolatey, winget) or manually:
+
+* CMake
+* Git
+* Python (3.x), plus the Python module `docutils`
+* Visual Studion 17 (2022), C/C++ Enviroment
+
+For example, to prepare the required tools with chocolatey, you
+can use the following commands (Powershell):
+
+    # Installing Chocolatey
+    Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1'))
+    & choco.exe install -y git --params "/GitAndUnixToolsOnPath"
+    & choco.exe install -y python
+    & python.exe -m ensurepip
+    & python.exe -m pip install --upgrade pip
+    & python.exe -m pip install docutils
+    & choco.exe install -y cmake --installargs 'ADD_CMAKE_TO_PATH=System'
+    & choco.exe install -y "visualstudio2022buildtools"
+    & choco.exe install -y "visualstudio2022-workload-vctools" --params "--add Microsoft.VisualStudio.Component.UWP.VC.ARM64 --add Microsoft.VisualStudio.Component.VC.Tools.ARM64 --add Microsoft.VisualStudio.Component.VC.ATL.Spectre --add Microsoft.VisualStudio.Component.VC.ATLMFC.Spectre --add Microsoft.VisualStudio.Component.VC.ATL.ARM64.Spectre --add Microsoft.VisualStudio.Component.VC.MFC.ARM64.Spectre --add Microsoft.VisualStudio.Component.VC.Runtimes.ARM64.Spectre --add Microsoft.VisualStudio.Component.VC.Runtimes.x86.x64.Spectre --quiet"
+    & choco.exe install -y windows-sdk-10-version-2004-windbg
+
+One or more restarts of Powershell might be required to pick up new additions
+to `PATH` between steps. A Windows restart is probably required after
+installing Visual Studio before being able to use it.
+You can find the exact commands we use to set up the community build machines
+at https://github.com/OpenVPN/openvpn-buildbot/blob/master/jenkins/windows-server/msibuild.pkr.hcl
+
+To do a default build, assuming you are in a MSVC 17 2022 environment:
+
+    mkdir C:\OpenVPN
+    cd C:\OpenVPN
+    git clone https://github.com/microsoft/vcpkg.git
+    git clone https://github.com/OpenVPN/openvpn.git
+    set VCPKG_ROOT=C:\OpenVPN\vcpkg
+    cd openvpn
+    cmake --preset win-amd64-release
+    cmake --build --preset win-amd64-release
+    ctest --preset win-amd64-release
+
+When using the presets, the build directory is
+`out/build/<preset-name>/`, you can find the output files there.
+No install support is provided directly in OpenVPN build, take a look
+at https://github.com/OpenVPN/openvpn-build.git instead.
+
+MinGW builds (cross-compile on Linux)
+-------------------------------------
+
+To build the Windows executables on a Linux system:
+
+    # install mingw with the package manager of your choice, e.g.
+    sudo apt-get install -y mingw-w64
+    # in addition to mingw we also need a toolchain for host builds, e.g.
+    sudo apt-get install -y build-essential
+    # minimum required tools for vcpkg bootstrap: curl, zip, unzip, tar, e.g.
+    sudo apt-get install -y curl zip unzip tar
+    # additionally vcpkg requires powershell when building Windows binaries.
+    # See https://learn.microsoft.com/en-us/powershell/scripting/install/installing-powershell-on-linux
+    # e.g.
+    sudo apt-get install -y wget apt-transport-https software-properties-common
+    wget -q "https://packages.microsoft.com/config/ubuntu/$(lsb_release -rs)/packages-microsoft-prod.deb"
+    sudo dpkg -i packages-microsoft-prod.deb
+    sudo apt-get update
+    sudo apt-get install -y powershell
+    # minimum required tools for build: cmake, docutils, git, ninja,
+    # pkg-config, python e.g.
+    sudo apt-get install -y cmake git ninja-build pkg-config python3 python3-docutils
+    # additionally required to build pkcs11-helper: automake, autoconf,
+    # man2html, e.g.
+    sudo apt-get install -y automake autoconf man2html-base
+    mkdir mingw
+    cd mingw
+    git clone https://github.com/microsoft/vcpkg.git
+    git clone https://github.com/OpenVPN/openvpn.git
+    export VCPKG_ROOT=$PWD/vcpkg
+    cd openvpn
+    cmake --preset mingw-x64
+    cmake --build --preset mingw-x64
+    # unit tests are built, but no testPreset is provided. You need to copy
+    # them to a Windows system manually
+
+The instructions have been verified on a Ubuntu 22.04 LTS system in a
+bash shell, and might need adaptions to other Linux distributions/versions.
+
+Note that the MinGW preset builds use the `Ninja multi-config` generator, so
+if you want to build the Debug binaries, use
+
+    cmake --build --preset mingw-x64 --config Debug
+
+The default build is equivalent to specifying `--config Release`.
+
+When using the presets, the build directory is
+`out/build/mingw/<arch>`, you can find the actual output files in
+sub-directories called `<buildtype>`.
+No install support is provided directly in OpenVPN build, take a look
+at https://github.com/OpenVPN/openvpn-build.git instead.
+
+Unsupported builds
+------------------
+
+The CMake buildsystem also supports builds on Unix-like platforms. These builds
+are sometimes useful for OpenVPN developers (e.g. when they use IDEs with
+integrated CMake support). However, they are not officially supported, do not
+include any install support and should not be used to distribute/package
+OpenVPN. To emphasize this fact, you need to specify `-DUNSUPPORTED_BUILDS=ON`
+to cmake to be able to use these builds.
+
+The `unix-native` CMake preset is available for these builds. This preset does
+not require VCPKG and instead assumes all build-dependencies are provided by
+the system natively.