Compiling with Mono

Requirements

• Mono 5.12.0 or greater
• MSBuild
• NuGet
• On Linux/macOS only: pkg-config

You may need to import necessary certificates for NuGet to perform HTTPS requests.

The recommended method is to use curl‘s CA (Certificate Autorities) certificate bundle.

Run the following commands to download and import it. On Windows, you can run it from the Mono command line prompt (or the regular prompt if you added Mono’s bin directory to your PATH environment variable):

# If using PowerShell, replace `curl` with `curl.exe` below.
curl -LO https://curl.haxx.se/ca/cacert.pem
cert-sync --user cacert.pem

Alternatively, you can use the following command, though it’s deprecated and may not work correctly:

mozroots --import --sync

Environment variables

By default, SCons will try to find Mono in the Windows Registry on Windows or via pkg-config on other platforms. You can specify a different installation directory by passing the mono_prefix command-line option to SCons; e.g. scons [...] mono_prefix=%ProgramFiles%/Mono.

This is the directory that contains the subdirectories include and lib.

Enable the Mono module

By default, the Mono module is disabled when building. To enable it, add the option module_mono_enabled=yes to the SCons command line.

Generate the glue

Glue sources are the wrapper functions that will be called by managed methods. These source files must be generated before building your final binaries. In order to generate them, first, you must build a temporary Godot binary with the options tools=yes and mono_glue=no:

scons p=<platform> tools=yes module_mono_enabled=yes mono_glue=no

After the build finishes, you need to run the compiled executable with the parameter --generate-mono-glue followed by the path to an output directory. This path must be modules/mono/glue in the Godot directory:

<godot_binary> --generate-mono-glue modules/mono/glue

This command will tell Godot to generate the file modules/mono/glue/mono_glue.gen.cpp and the C# solution for the Godot API at modules/mono/glue/Managed/Generated. Once these files are generated, you can build Godot for all the desired targets without having to repeat this process.

<godot_binary> refers to the tools binary you compiled above with the Mono module enabled. Its exact name will differ based on your system and configuration, but should be of the form bin/godot.<platform>.tools.<bits>.mono, e.g. bin/godot.x11.tools.64.mono or bin/godot.windows.tools.64.mono.exe. Be especially aware of the .mono suffix! If you’ve previously compiled Godot without Mono support, you might have similarly named binaries without this suffix. These binaries can’t be used to generate the Mono glue.

Notes

• Do not build your final binaries with mono_glue=no. This disables C# scripting. This option must be used only for the temporary binary that will generate the glue. Godot will print a warning at startup if it was built without the glue sources.
• The glue sources must be regenerated every time the ClassDB-registered API changes. That is, for example, when a new method is registered to the scripting API or one of the parameters of such a method changes. Godot will print an error at startup if there is an API mismatch between ClassDB and the glue sources.

Rebuild with Mono glue

Once you have generated the Mono glue, you can build the final binary with mono_glue=yes. This is the default value for mono_glue, so you can also omit it. To build a Mono-enabled editor:

scons p=<platform> tools=yes module_mono_enabled=yes mono_glue=yes

And Mono-enabled export templates:

scons p=<platform> tools=no module_mono_enabled=yes mono_glue=yes

If everything went well, apart from the normal output, SCons should have created the following files in the bin directory:

• If you’re not linking the Mono runtime statically, the build script will place the Mono runtime shared library (monosgen-2.0) next to the Godot binary in the output directory. Make sure to include this library when distributing Godot. When targeting Android, no extra steps are required as this library is automatically copied to #platform/android/java/libs and Gradle takes care of the rest.
• Unlike “classical” Godot builds, when building with the Mono module enabled (and depending on the target platform), a data directory may be created both for the editor and for export templates. This directory is important for proper functioning and must be distributed together with Godot. More details about this directory in Data directory.

Examples

Example (Windows)

# Build temporary binary
scons p=windows tools=yes module_mono_enabled=yes mono_glue=no
# Generate glue sources
bin\godot.windows.tools.64.mono --generate-mono-glue modules/mono/glue
### Build binaries normally
# Editor
scons p=windows target=release_debug tools=yes module_mono_enabled=yes
# Export templates
scons p=windows target=release_debug tools=no module_mono_enabled=yes
scons p=windows target=release tools=no module_mono_enabled=yes

Example (X11)

# Build temporary binary
scons p=x11 tools=yes module_mono_enabled=yes mono_glue=no
# Generate glue sources
bin/godot.x11.tools.64.mono --generate-mono-glue modules/mono/glue
### Build binaries normally
# Editor
scons p=x11 target=release_debug tools=yes module_mono_enabled=yes
# Export templates
scons p=x11 target=release_debug tools=no module_mono_enabled=yes
scons p=x11 target=release tools=no module_mono_enabled=yes

Data directory

The data directory is a dependency for Godot binaries built with the Mono module enabled. It contains important files for the correct functioning of Godot. It must be distributed together with the Godot executable.

Note

The information below doesn’t apply for Android, iOS and WASM, as there is no data directory for these platforms.

Export templates

The name of the data directory for an export template differs based on the configuration it was built with. The format is data.mono.<platform>.<bits>.<target>, e.g. data.mono.x11.32.release_debug or data.mono.windows.64.release.

This directory must be placed with its original name next to the Godot export templates. When exporting a project, Godot will also copy this directory with the game executable but the name will be changed to data_<APPNAME>, where <APPNAME> is the application name as specified in the project setting application/config/name.

In the case of macOS, where the export template is compressed as a ZIP archive, the contents of the data directory can be placed in the following locations inside the ZIP archive:

Editor

The name of the data directory for the Godot editor will always be GodotSharp. The contents of this directory are the following:

• Api
• Mono (optional)
• Tools

The Api subdirectory contains the Godot API assemblies. On macOS, if the Godot editor is distributed as a bundle, the contents of the data directory may be placed in the following locations:

The Mono subdirectory is optional. It will be needed when distributing the editor, as issues can arise when the user-installed Mono version isn’t identical to the one the Godot editor was built with. Pass copy_mono_root=yes to SCons when building the editor in order to create this folder and its contents.

The Tools subdirectory contains tools required by the editor, like the GodotTools assemblies and its dependencies.

Building the Mono runtime

When building Godot for the desktop, you will likely use the pre-built Mono runtime that is installed on your system. This likely won’t be the case when targeting other platforms like Android, iOS and WebAssembly. You will have to build the Mono runtime yourself for those platforms.

We recommend using these build scripts. They simplify this process but also include some patches needed for proper functioning with Godot. See the README on the link above for instructions on how to use the scripts.

Targeting Android

Compiling the Android export templates with Mono is a bit simpler than it is for the desktop platforms, as there are no additional steps required after building. There is no need to worry about run-time dependencies like a data directory or the shared library (when dynamically linking) as those are automatically added to the Gradle project.

Once you’ve built Mono, you can proceed to build Godot with the instructions described in this page and the Compiling for Android page. Make sure to let SCons know about the location of the Mono runtime you’ve just built, e.g.: scons [...] mono_prefix="$HOME/mono-installs/android-armeabi-v7a-release" (This path may be different on your system).

Targeting iOS

Once you’ve built Mono, you can proceed to build Godot with the instructions described in this page and the Compiling for iOS page. Make sure to let SCons know about the location of the Mono runtime you’ve just built, e.g.: scons [...] mono_prefix="$HOME/mono-installs/ios-arm64-release" (This path may be different on your system).

After building Godot for each architecture, you will notice SCons has copied the Mono libraries for each of them to the output directory:

#bin/libmono-native.iphone.<arch>.a
#bin/libmonosgen-2.0.iphone.<arch>.a
#bin/libmonoprofiler-log.iphone.<arch>.a
#bin/libmono-ilgen.iphone.<arch>.a
#bin/libmono-ee-interp.iphone.<arch>.a
#bin/libmono-icall-table.iphone.<arch>.a

The last three are only for iOS devices and are not available for the iOS simulator.

These libraries must be put in universal (multi-architecture) “fat” files to be distributed with the export templates.

The following bash script will create the “fat” libraries in the directory #bin/ios/iphone-mono-libs:

mkdir -p bin/ios
mkdir -p bin/ios/iphone-mono-libs
lipo -create bin/libmonosgen-2.0.iphone.arm64.a bin/libmonosgen-2.0.iphone.x86_64.a -output bin/ios/iphone-mono-libs/libmonosgen-2.0.iphone.fat.a
lipo -create bin/libmono-native.iphone.arm64.a bin/libmono-native.iphone.x86_64.a -output bin/ios/iphone-mono-libs/libmono-native.iphone.fat.a
lipo -create bin/libmono-profiler-log.iphone.arm64.a bin/libmono-profiler-log.iphone.x86_64.a -output bin/ios/iphone-mono-libs/libmono-profiler-log.iphone.fat.a
# The Mono libraries for the interpreter are not available for simulator builds
lipo -create bin/libmono-ee-interp.iphone.arm64.a -output bin/ios/iphone-mono-libs/libmono-ee-interp.iphone.fat.a
lipo -create bin/libmono-icall-table.iphone.arm64.a -output bin/ios/iphone-mono-libs/libmono-icall-table.iphone.fat.a
lipo -create bin/libmono-ilgen.iphone.arm64.a -output bin/ios/iphone-mono-libs/libmono-ilgen.iphone.fat.a

The iphone-mono-libs folder must be distributed with the export templates. The Godot editor will look for the libraries in <templates>/iphone-mono-libs/lib<name>.iphone.fat.a.

Targeting WebAssembly

Building for WebAssembly currently involves the same process regardless of whether the Mono module is enabled.

Once you’ve built Mono, you can proceed to build Godot with the instructions described in this page and the Compiling for the Web page. Make sure to let SCons know about the location of the Mono runtime you’ve just built, e.g.: scons [...] mono_prefix="$HOME/mono-installs/wasm-runtime-release" (This path may be different on your system).

Base Class Library

The export templates must also include the BCL (Base Class Library) for each target platform. Godot looks for the BCL folder at <templates>/bcl/<target_platform>, where <target_platform> is the same name passed to the SCons platform option, e.g.: <templates>/bcl/windows, <templates>/bcl/javascript.

Alternatively, Godot will look for them in the following locations:

As of now, we’re assuming the same BCL profile can be used for both Linux and macOS, but this may change in the future as they’re not guaranteed to be the same (as is the case with the Windows BCL).

If the target platform is the same as the platform of the Godot editor, then the editor will use the BCL it’s running on (<data_folder>/Mono/lib/mono/4.5) if it cannot find the BCL in the export templates.

AOT cross-compilers

To perform ahead-of-time (AOT) compilation for other platforms, Godot needs to have access to the Mono cross-compilers for that platform and architecture.

Godot will look for the cross-compiler executable in the AOT compilers folder. The location of this folder is <data_folder>/Tools/aot-compilers/.

In order to build the cross-compilers we recommend using these build scripts.

After building them, copy the executable to the Godot AOT compilers directory. The executable name is <triple>-mono-sgen, e.g.: aarch64-apple-darwin-mono-sgen.

Command-line options

The following is the list of command-line options available when building with the Mono module:

• module_mono_enabled\=yes | no
  • Build Godot with the Mono module enabled.
• mono_glue\=yes | no
  • Whether to include the glue source files in the build and define MONO_GLUE_DISABLED as a preprocessor macro.
• mono_prefix\=path
  • Path to the Mono installation directory for the target platform and architecture.
• xbuild_fallback\=yes | no
  • Whether to fallback to xbuild if MSBuild is not available.
• mono_static\=yes | no
  • Whether to link the Mono runtime statically.
  • The default is yes for iOS and WASM, and no for other platforms.
• copy_mono_root\=yes | no
  • Whether to copy the Mono framework assemblies and configuration files required by the Godot editor.