godot-docs/contributing/development/compiling/compiling_with_mono.rst

.. _doc_compiling_with_mono:

Compiling with Mono
===================

.. highlight:: shell

Requirements
------------

- Mono 6.12.0 or greater (generally 64 bit)
- MSBuild
- NuGet
- **On Linux/macOS only:** pkg-config

You can use ``mono -V`` to check your Mono version.
A build error like the one below may indicate your Mono version is too old:

    'mono_runtime_set_pending_exception': identifier not found

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

The recommended method is to use **curl**'s CA (Certificate Authorities) 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``.
Note that as usual, paths including spaces must be wrapped in double quotes.

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 ``target=editor``::

    scons p=<platform> target=editor module_mono_enabled=yes

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

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

This command will tell Godot to generate the file ``modules/mono/glue/mono_glue.gen.cpp``,
the C# solution for the Godot API at ``modules/mono/glue/GodotSharp/GodotSharp/Generated``,
and the C# solution for the editor tools at ``modules/mono/glue/GodotSharp/GodotSharpEditor/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 editor 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>.editor.<arch>.mono``, e.g. ``bin/godot.linuxbsd.editor.x86_64.mono``
or ``bin/godot.windows.editor.x86_32.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
^^^^^

- 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 generate the final binary with
the ``build_assemblies.py`` script.::

    ./modules/mono/build_scripts/build_assemblies.py --godot-output-dir=./bin --godot-platform={PLATFORM_NAME}

And Mono-enabled export templates::

    scons p=<platform> target=template_release module_mono_enabled=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 the Godot editor or export templates.**
  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
  :ref:`Data directory<compiling_with_mono_data_directory>`.

Examples
--------

Example (Windows)
^^^^^^^^^^^^^^^^^

::

    # Build editor binary
    scons p=windows target=editor module_mono_enabled=yes
    # Generate glue sources
    bin\godot.windows.editor.x86_64.mono --generate-mono-glue modules/mono/glue
    # Build .NET assemblies
    ./modules/mono/build_scripts/build_assemblies.py --godot-output-dir=./bin --godot-platform=windows

    ### Build binaries normally
    # Editor
    scons p=windows target=editor module_mono_enabled=yes
    # Export templates
    scons p=windows target=template_debug module_mono_enabled=yes
    scons p=windows target=template_release module_mono_enabled=yes

Example (Linux, \*BSD)
^^^^^^^^^^^^^^^^^^^^^^

::

    # Build temporary binary
    scons p=linuxbsd target=editor module_mono_enabled=yes
    # Generate glue sources
    bin/godot.linuxbsd.editor.x86_64.mono --generate-mono-glue modules/mono/glue
    # Generate binaries
    ./modules/mono/build_scripts/build_assemblies.py --godot-output-dir=./bin --godot-platform=linuxbsd

    ### Build binaries normally
    # Editor
    scons p=linuxbsd target=editor module_mono_enabled=yes
    # Export templates
    scons p=linuxbsd target=template_debug module_mono_enabled=yes
    scons p=linuxbsd target=template_release module_mono_enabled=yes

.. _compiling_with_mono_data_directory:

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>.<arch>.<target>``, e.g. ``data.mono.linuxbsd.x86_32.release_debug`` or
``data.mono.windows.x86_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:

+-------------------------------------------------------+---------------------------------------------------------------+
| ``bin/data.mono.<platform>.<arch>.<target>/Mono/lib`` | ``/osx_template.app/Contents/Frameworks/GodotSharp/Mono/lib`` |
+-------------------------------------------------------+---------------------------------------------------------------+
| ``bin/data.mono.<platform>.<arch>.<target>/Mono/etc`` | ``/osx_template.app/Contents/Resources/GodotSharp/Mono/etc``  |
+-------------------------------------------------------+---------------------------------------------------------------+

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:

+-------------------------------------------------------+---------------------------------------------------------------+
| ``bin/data.mono.<platform>.<arch>.<target>/Api``      | ``<bundle_name>.app/Contents/Frameworks/GodotSharp/Api``      |
+-------------------------------------------------------+---------------------------------------------------------------+
| ``bin/data.mono.<platform>.<arch>.<target>/Mono/lib`` | ``<bundle_name>.app/Contents/Frameworks/GodotSharp/Mono/lib`` |
+-------------------------------------------------------+---------------------------------------------------------------+
| ``bin/data.mono.<platform>.<arch>.<target>/Mono/etc`` | ``<bundle_name>.app/Contents/Resources/GodotSharp/Mono/etc``  |
+-------------------------------------------------------+---------------------------------------------------------------+
| ``bin/data.mono.<platform>.<arch>.<target>/Tools``    | ``<bundle_name>.app/Contents/Frameworks/GodotSharp/Tools``    |
+-------------------------------------------------------+---------------------------------------------------------------+

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 <https://github.com/godotengine/godot-mono-builds>`_.
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
:ref:`Compiling for Android<doc_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
:ref:`Compiling for iOS<doc_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
:ref:`Compiling for the Web<doc_compiling_for_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:

+-------------------+---------------------------------+
|      Android      |  ``<templates>/bcl/monodroid``  |
+-------------------+---------------------------------+
|        iOS        |  ``<templates>/bcl/monotouch``  |
+-------------------+---------------------------------+
|    WebAssembly    |    ``<templates>/bcl/wasm``     |
+-------------------+---------------------------------+
|  Linux and macOS  |   ``<templates>/bcl/net_4_x``   |
+-------------------+---------------------------------+
|      Windows      | ``<templates>/bcl/net_4_x_win`` |
+-------------------+---------------------------------+

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 <https://github.com/godotengine/godot-mono-builds>`_.

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_prefix**\ =path

  - Path to the Mono installation directory for the target platform and architecture.

- **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.