Mono Project ORG

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Mono is a software platform designed to allow developers to easily create cross platform applications. It is an open source implementation of Microsoft's .NET Framework based on the ECMA standards…

Mono is a software platform designed to allow developers to easily
create cross platform applications. It is an open source
implementation of Microsoft's .NET Framework based on the ECMA
standards for C# and the Common Language Runtime.

The Mono project is part of the .NET Foundation

> [!IMPORTANT]
> The [Mono Project (mono/mono)]( https://github.com/mono/mono) (‘original mono’) has been an important part of the .NET ecosystem since it was launched in 2001. Microsoft became the steward of the Mono Project when it acquired Xamarin in 2016.
>
> The last major release of the Mono Project was in July 2019, with minor patch releases since that time. The last patch release was February 2024.
>
> We are happy to announce that the WineHQ organization will be taking over as the stewards of the Mono Project upstream at wine-mono / Mono · GitLab (winehq.org). Source code in existing mono/mono and other repos will remain available, although repos may be archived. Binaries will remain available for up to four years.
>
> Microsoft maintains a modern fork of Mono runtime in the dotnet/runtime repo and has been progressively moving workloads to that fork. That work is now complete, and we recommend that active Mono users and maintainers of Mono-based app frameworks migrate to .NET which includes work from this fork.
>
> We want to recognize that the Mono Project was the first .NET implementation on Android, iOS, Linux, and other operating systems. The Mono Project was a trailblazer for the .NET platform across many operating systems. It helped make cross-platform .NET a reality and enabled .NET in many new places and we appreciate the work of those who came before us.
>
> Thank you to all the Mono developers!

Join us on Discord in the #monovm channel:

1. [Compilation and Installation](#compilation-and-installation)
2. [Using Mono](#using-mono)
3. [Directory Roadmap](#directory-roadmap)
4. [Contributing to Mono](#contributing-to-mono)
5. [Reporting bugs](#reporting-bugs)
6. [Configuration Options](#configuration-options)
7. [Working with Submodules](#working-with-submodules)

Build Status

Public CI: ![Azure Pipelines](https://dev.azure.com/dnceng/public/_build/latest?definitionId=952&branchName=main)

Legacy Jenkins CI (no longer available publicly):

| OS | Architecture | Status |
|--------------|--------------------|------------------------------|
| Debian 9 | amd64 | [![debian-9-amd64][1]][2] |
| Debian 9 | i386 | [![debian-9-i386][3]][4] |
| Debian 9 | armel | [![debian-9-armel][5]][6] |
| Debian 9 | armhf | [![debian-9-armhf][7]][8] |
| Debian 9 | arm64 | [![debian-9-arm64][9]][10] |
| OS X | amd64 | [![osx-amd64][11]][12] |
| OS X | i386 | [![osx-i386][13]][14] |
| Windows | amd64 | [![windows-amd64][15]][16] |
| Windows | i386 | [![windows-i386][17]][18] |
| CentOS | s390x (cs) | [![centos-s390x][19]][20] |
| Debian 9 | ppc64el (cs) | [![debian-9-ppc64el][21]][22]|
| AIX 6.1 | ppc64 (cs) | [![aix-ppc64][23]][24] |
| FreeBSD 12 | amd64 (cs) | [![freebsd-amd64][25]][26] |

_(cs) = community supported architecture_

Compilation and Installation
============================

Building the Software
---------------------

Please see our guides for building Mono on
Mac OS X,
Linux and
Windows.

Note that building from Git assumes that you already have Mono installed,
so please download and install the latest Mono release
before trying to build from Git. This is required because the Mono build
relies on a working Mono C# compiler to compile itself
(also known as bootstrapping)).

If you don't have a working Mono installation
---------------------------------------------

If you don't have a working Mono installation, you can try a slightly
more risky approach: getting the latest version of the 'monolite' distribution,
which contains just enough to run the 'mcs' compiler. You do this with:

# Run the following line after ./autogen.sh
make get-monolite-latest

This will download and place the files appropriately so that you can then
just run:

make

The build will then use the files downloaded by make get-monolite-latest.

Testing and Installation
------------------------

You can run the mono and mcs test suites with the command: make check.

Expect to find a few test suite failures. As a sanity check, you
can compare the failures you got with https://jenkins.mono-project.com/.

You can now install mono with: make install

You can verify your installation by using the mono-test-install
script, it can diagnose some common problems with Mono's install.
Failure to follow these steps may result in a broken installation.

Using Mono
==========

Once you have installed the software, you can run a few programs:

mono program.exe runtime engine

mcs program.cs C# compiler

monodis program.exe CIL Disassembler

See the man pages for mono(1), mcs(1) and monodis(1) for further details.

Directory Roadmap
=================

acceptance-tests/ - Optional third party test suites used to validate Mono against a wider range of test cases.

data/ - Configuration files installed as part of the Mono runtime.

docs/ - Technical documents about the Mono runtime.

external/ - Git submodules for external libraries (Newtonsoft.Json, ikvm, etc).

ikvm-native/ - Glue code for ikvm.

libgc/ - The (deprecated) Boehm GC implementation.

llvm/ - Utility Makefiles for integrating the Mono LLVM fork.

m4/ - General utility Makefiles.

man/ - Manual pages for the various Mono commands and programs.

mcs/ - The class libraries, compiler and tools

* class/ - The class libraries (like System.*, Microsoft.Build, etc.)

* mcs/ - The Mono C# compiler written in C#

* tools/ - Tools like gacutil, ikdasm, mdoc, etc.

mono/ - The core of the Mono Runtime.

* arch/ - Architecture specific portions.

* benchmark/ - A collection of benchmarks.

* btls/ - Build files for the BTLS library which incorporates BoringSSL.

* cil/ - Common Intermediate Representation, XML
definition of the CIL bytecodes.

* dis/ - CIL executable Disassembler.

* eglib/ - Independent implementation of the glib API.

* metadata/ - The object system and metadata reader.

* mini/ - The Just in Time Compiler.

* profiler/ - The profiler implementation.

* sgen/ - The SGen Garbage Collector implementation.

* tests/ - The main runtime tests.

* unit-tests/ - Additional runtime unit tests.

* utils/ - Utility functions used across the runtime codebase.

msvc/ - Logic for the MSVC / Visual Studio based runtime and BCL build system.

The latter is experimental at the moment.

packaging/ - Packaging logic for the OS X and Windows Mono packages.

po/ - Translation files.

runtime/ - A directory that contains the Makefiles that link the

mono/ and mcs/ build systems.

samples/ - Some simple sample programs on uses of the Mono

runtime as an embedded library.

scripts/ - Scripts used to invoke Mono and the corresponding program.

support/ - Various support libraries.

tools/ - A collection of tools, mostly used during Mono development.

Contributing to Mono ====================

Before submitting changes to Mono, please review the contribution
guidelines.
Please pay particular attention to the Important
Rules
section.

Reporting bugs
==============

To submit bug reports, please open an issue on the mono GitHub repo.

Please use the search facility to ensure the same bug hasn't already
been submitted and follow our
guidelines
on how to make a good bug report.

Configuration Options
=====================

The following are the configuration options that someone building Mono
might want to use:

--with-sgen=yes,no - Generational GC support: Used to enable or

disable the compilation of a Mono runtime with the SGen garbage collector.

* On platforms that support it, after building Mono, you will have
both a mono-boehm binary and a mono-sgen binary. mono-boehm uses Boehm,
while mono-sgen uses the Simple Generational GC.

--with-libgc=[included, none] - Selects the default Boehm

garbage collector engine to use.

* *included*: (*slightly modified Boehm GC*) This is the default
value for the Boehm GC, and it's the most feature complete, it will
allow Mono to use typed allocations and support the debugger.

* *none*:
Disables the inclusion of a Boehm garbage collector.

* This defaults to included.

--enable-cooperative-suspend

* If you pass this flag the Mono runtime is configured to only use the cooperative mode of the garbage collector. If you do not pass this flag, then you can control at runtime the use of the cooperative GC mode by setting the MONO_ENABLE_COOP_SUSPEND flag.

--with-tls=__thread,pthread

* Controls how Mono should access thread local storage, pthread forces Mono to use the pthread APIs, while __thread uses compiler-optimized access to it.

* Although __thread is faster, it requires support from
the compiler, kernel and libc. Old Linux systems do
not support with __thread.

* This value is typically pre-configured and there is no
need to set it, unless you are trying to debug a problem.

--with-sigaltstack=yes,no

* Experimental: Use at your own risk, it is known to cause problems with garbage collection and is hard to reproduce those bugs.

* This controls whether Mono will install a special
signal handler to handle stack overflows. If set to
yes, it will turn stack overflows into the
StackOverflowException. Otherwise when a stack
overflow happens, your program will receive a
segmentation fault.

* The configure script will try to detect if your
operating system supports this. Some older Linux
systems do not support this feature, or you might want
to override the auto-detection.

--with-static_mono=yes,no

* This controls whether mono should link against a static library (libmono.a) or a shared library (libmono.so).

* This defaults to yes, and will improve the performance
of the mono program.

* This only affects the mono' binary, the shared library libmono.so will always be produced for developers that want to embed the runtime in their application.

--with-xen-opt=yes,no - Optimize code for Xen virtualization.


  * It makes Mono generate code which might be slightly
slower on average systems, but the resulting executable will run
faster under the Xen virtualization system.

* This defaults to yes.

--with-large-heap=yes,no - Enable support for GC heaps larger than 3GB.


  * This only applies only to the Boehm garbage collector, the SGen garbage
collector does not use this configuration option.

* This defaults to no.

--enable-small-config=yes,no - Enable some tweaks to reduce memory usage

and disk footprint at the expense of some capabilities.
* Typically this means that the number of threads that can be created
is limited (256), that the maximum heap size is also reduced (256 MB)
and other such limitations that still make mono useful, but more suitable
to embedded devices (like mobile phones).

* This defaults to no.

--with-ikvm-native=yes,no - Controls whether the IKVM JNI interface library is

built or not.
* This is used if you are planning on
using the IKVM Java Virtual machine with Mono.

* This defaults to yes.

--with-profile4=yes,no - Whether you want to build the 4.x profile libraries

and runtime.

* This defaults to yes.

--with-libgdiplus=installed,sibling, - Configure where Mono

searches for libgdiplus when running System.Drawing tests.

* It defaults to installed, which means that the library is available to Mono through the regular system setup.

* siblingcan be used to specify that a libgdiplus that resides as a sibling of this directory (mono) should be used.


* Or you can specify a path to a libgdiplus.

--enable-minimal=LIST


  * Use this feature to specify optional runtime
components that you might not want to include.  This
is only useful for developers embedding Mono that
require a subset of Mono functionality.
  * The list is a comma-separated list of components that
should be removed, these are:

* aot: Disables support for the Ahead of Time compilation.

* attach`:
Support for the Mono.Manag

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