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https://github.com/mono/mono

Mono open source ECMA CLI, C# and .NET implementation.
https://github.com/mono/mono

android csharp dotnet garbage-collector ios jit runtime xamarin

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Mono open source ECMA CLI, C# and .NET implementation.

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README 

        
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](https://www.dotnetfoundation.org/)



> [!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)](https://gitlab.winehq.org/wine-mono/mono).  Source code in existing [mono/mono](https://github.com/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](https://github.com/dotnet/runtime/tree/main/src/mono) 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](https://github.com/dotnet/core) 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](https://aka.ms/dotnet-discord) in the `#monovm` channel:





  




### Contents



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/_apis/build/status/mono/mono-ci?branchName=main)](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_



[1]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-amd64/badge/icon

[2]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-amd64

[3]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-i386/badge/icon

[4]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-i386/

[5]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-armel/badge/icon

[6]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-armel/

[7]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-armhf/badge/icon

[8]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-armhf/

[9]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-arm64/badge/icon

[10]: https://jenkins.mono-project.com/job/test-mono-mainline-linux/label=debian-9-arm64/

[11]: https://jenkins.mono-project.com/job/test-mono-mainline/label=osx-amd64/badge/icon

[12]: https://jenkins.mono-project.com/job/test-mono-mainline/label=osx-amd64/

[13]: https://jenkins.mono-project.com/job/test-mono-mainline/label=osx-i386/badge/icon

[14]: https://jenkins.mono-project.com/job/test-mono-mainline/label=osx-i386/

[15]: https://jenkins.mono-project.com/job/z/label=w64/badge/icon

[16]: https://jenkins.mono-project.com/job/z/label=w64/

[17]: https://jenkins.mono-project.com/job/z/label=w32/badge/icon

[18]: https://jenkins.mono-project.com/job/z/label=w32/

[19]: https://jenkins.mono-project.com/job/test-mono-mainline-community/label=centos-s390x/badge/icon

[20]: https://jenkins.mono-project.com/job/test-mono-mainline-community/label=centos-s390x

[21]: https://jenkins.mono-project.com/job/test-mono-mainline-community-chroot/label=debian-9-ppc64el/badge/icon

[22]: https://jenkins.mono-project.com/job/test-mono-mainline-community-chroot/label=debian-9-ppc64el

[23]: https://jenkins.mono-project.com/job/test-mono-mainline-community/label=aix-ppc64/badge/icon

[24]: https://jenkins.mono-project.com/job/test-mono-mainline-community/label=aix-ppc64

[25]: https://jenkins.mono-project.com/job/test-mono-mainline-community/label=freebsd-12-amd64/badge/icon

[26]: https://jenkins.mono-project.com/job/test-mono-mainline-community/label=freebsd-12-amd64



Compilation and Installation

============================



Building the Software

---------------------



Please see our guides for building Mono on

[Mac OS X](https://www.mono-project.com/docs/compiling-mono/mac/),

[Linux](https://www.mono-project.com/docs/compiling-mono/linux/) and 

[Windows](https://www.mono-project.com/docs/compiling-mono/windows/).



Note that building from Git assumes that you already have Mono installed,

so please download and [install the latest Mono release](https://www.mono-project.com/download/)

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](https://en.wikipedia.org/wiki/Bootstrapping_(compilers))).



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/](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](https://www.mono-project.com/community/contributing/).

Please pay particular attention to the [Important

Rules](https://www.mono-project.com/community/contributing/#important-rules)

section.



Reporting bugs

==============



To submit bug reports, please [open an issue on the mono GitHub repo](https://github.com/mono/mono/issues/new).



Please use the search facility to ensure the same bug hasn't already

been submitted and follow our

[guidelines](https://www.mono-project.com/community/bugs/make-a-good-bug-report/)

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.



  * `sibling` can 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.Management assembly and the

VMAttach API (allowing code to be injected into

a target VM)



    * `com`:

Disables COM support.



    * `debug`:

Drop debugging support.



    * `decimal`:

Disables support for System.Decimal.



    * `full_messages`:

By default Mono comes with a full table

of messages for error codes. This feature

turns off uncommon error messages and reduces

the runtime size.



    * `generics`:

Generics support.  Disabling this will not

allow Mono to run any 2.0 libraries or

code that contains generics.



    * `jit`:

Removes the JIT engine from the build, this reduces

the executable size, and requires that all code

executed by the virtual machine be compiled with

Full AOT before execution.



    * `large_code`:

Disables support for large assemblies.



    * `logging`:

Disables support for debug logging.



    * `pinvoke`:

Support for Platform Invocation services,

disabling this will drop support for any

libraries using DllImport.



    * `portability`:

Removes support for MONO_IOMAP, the environment

variables for simplifying porting applications that 

are case-insensitive and that mix the Unix and Windows path separators.



    * `profiler`:

Disables support for the default profiler.



    * `reflection_emit`:

Drop System.Reflection.Emit support



    * `reflection_emit_save`:

Drop support for saving dynamically created

assemblies (AssemblyBuilderAccess.Save) in

System.Reflection.Emit.



    * `shadow_copy`:

Disables support for AppDomain's shadow copies

(you can disable this if you do not plan on 

using appdomains).



    * `simd`:

Disables support for the Mono.SIMD intrinsics

library.



    * `ssa`:

Disables compilation for the SSA optimization

framework, and the various SSA-based optimizations.



* `--enable-llvm`



  * This enables the use of LLVM as a code generation engine

for Mono.  The LLVM code generator and optimizer will be 

used instead of Mono's built-in code generator for both

Just in Time and Ahead of Time compilations.



  * See https://www.mono-project.com/docs/advanced/mono-llvm/ for the 

full details and up-to-date information on this feature.



  * You will need to have an LLVM built that Mono can link

against.



* `--enable-big-arrays` - Enable use of arrays with indexes larger

than Int32.MaxValue.



  * By default Mono has the same limitation as .NET on

Win32 and Win64 and limits array indexes to 32-bit

values (even on 64-bit systems).



  * In certain scenarios where large arrays are required,

you can pass this flag and Mono will be built to

support 64-bit arrays.



  * This is not the default as it breaks the C embedding

ABI that we have exposed through the Mono development

cycle.



* `--enable-parallel-mark`



  * Use this option to enable the garbage collector to use

multiple CPUs to do its work.  This helps performance

on multi-CPU machines as the work is divided across CPUS.



  * This option is not currently the default on OSX

as it runs into issues there.



  * This option only applies to the Boehm GC.



* `--enable-dtrace`



  * On Solaris and MacOS X builds a version of the Mono

runtime that contains DTrace probes and can

participate in the system profiling using DTrace.



* `--disable-dev-random`



  * Mono uses /dev/random to obtain good random data for

any source that requires random numbers.   If your

system does not support this, you might want to

disable it.



  * There are a number of runtime options to control this

also, see the man page.



* `--with-csc=roslyn,mcs,default`



  * Use this option to configure which C# compiler to use.  By default

    the configure script will pick Roslyn, except on platforms where

    Roslyn does not work (Big Endian systems) where it will pick mcs.



    If you specify "mcs", then Mono's C# compiler will be used.  This

    also allows for a complete bootstrap of Mono's core compiler and

    core libraries from source.



    If you specify "roslyn", then Roslyn's C# compiler will be used.

    This currently uses Roslyn binaries.

  

* `--enable-nacl`



  * This configures the Mono compiler to generate code

suitable to be used by Google's Native Client:

https://code.google.com/p/nativeclient/



  * Currently this is used with Mono's AOT engine as

Native Client does not support JIT engines yet.



* `--enable-wasm`



  * Use this option to configure mono to run on WebAssembly. It will

    set both host and target to the WebAssembly triplet. This overrides

    the values passed to `--host` or `--target` and ignored what config.sub guesses.



    This is a workaround to enable usage of old automake versions that don't

    recognize the wasm triplet.



Working With Submodules

=======================



Mono references several external git submodules, for example

a fork of Microsoft's reference source code that has been altered

to be suitable for use with the Mono runtime.



This section describes how to use it.



An initial clone should be done recursively so all submodules will also be

cloned in a single pass:



	$ git clone --recursive [email protected]:mono/mono



Once cloned, submodules can be updated to pull down the latest changes.

This can also be done after an initial non-recursive clone:



	$ git submodule update --init --recursive



To pull external changes into a submodule:



	$ cd 

	$ git pull origin 

	$ cd 

	$ git add 

	$ git commit



By default, submodules are detached because they point to a specific commit.

Use `git checkout` to move back to a branch before making changes:



	$ cd 

	$ git checkout 

	# work as normal; the submodule is a normal repo

	$ git commit/push new changes to the repo (submodule)



	$ cd 

	$ git add  # this will record the new commits to the submodule

	$ git commit



To switch the repo of a submodule (this should not be a common or normal thing

to do at all), first edit `.gitmodules` to point to the new location, then:



	$ git submodule sync -- 

	$ git submodule update --recursive

	$ git checkout 



The desired output diff is a change in `.gitmodules` to reflect the

change in the remote URL, and a change in / where you see

the desired change in the commit hash.



License

=======



See the LICENSE file for licensing information, and the PATENTS.TXT

file for information about Microsoft's patent grant.



Mono Trademark Use Policy

=========================



The use of trademarks and logos for Mono can be found [here](https://www.dotnetfoundation.org/legal/mono-tm).