Basics
The Ximian Role in the Mono project
Mono and GNOME
Building GUI applications with Mono
Mono and Microsoft
Mono platforms
Mono and the Portable.NET Project
Web Services
Mono and ASP.NET
Mono and ADO.NET
MonoDoc
Development Tools and Issues
Mono and Java
Extending Mono
Portability
Reusing Existing Code
Mono and GCC
Performance
Licensing
Patents
Miscellaneous Questions
Mono Common Problems
A Spanish
translation is also available
** Basics
Q: What is Mono exactly?
A: The Mono Project is an open development initiative sponsored by
Ximian that is working to develop an open source, Unix
version of the Microsoft .NET development platform. Its objective
is to enable Unix developers to build and
deploy cross-platform .NET Applications. The project will
implement various technologies developed by Microsoft that have now
been submitted to the ECMA for standardization.
Q: What is the difference between Mono and the .NET Initiative?
A: The ".NET Initiative" is a somewhat nebulous company-wide effort by
Microsoft, one part of which is a cross-platform development
framework. Mono is an implementation of the development framework,
but not an implementation of anything else related to the .NET
Initiative, such as Passport, software-as-a-service, or
corporate re-branding.
Q: What technologies are included in Mono?
A: Mono contains a number of components useful for building new
software:
* A Common Language Infrastructure (CLI) virtual
machine that contains a class loader, Just-in-time
compiler, and a garbage collecting runtime.
* A class library that can work with any language
which works on the CLR.
* A compiler for the C# language. In the future we
might work on other compilers that target the Common
Language Runtime.
Windows has compilers that target the virtual machine from a
number of languages: Managed C++, Java Script, Eiffel,
Component Pascal, APL, Cobol, Perl, Python, Scheme,
Smalltalk, Standard ML, Haskell, Mercury and Oberon.
The CLR and the Common Type System (CTS) enables applications and
libraries to be written in a collection of different languages that
target the byte code
This means for example that if you define a class to do algebraic
manipulation in C#, that class can be reused from any other
language that supports the CLI. You could create a class in C#,
subclass it in C++ and instantiate it in an Eiffel program.
A single object system, threading system, class libraries, and
garbage collection system can be shared across all these languages.
Q: Where can I find the specification for these technologies?
A: You can find the information here:
C# http://www.ecma.ch/ecma1/STAND/ecma-334.htm
CLI http://www.ecma.ch/ecma1/STAND/ecma-335.htm
Q: Will you implement the .NET Framework SDK class libraries?
A: Yes, we will be implementing the APIs of the .NET Framework SDK
class libraries.
Q: Will you offer an ECMA-compliant set of class libraries?
A: Eventually we will. Our current focus is on inter-operating
with the Microsoft SDK, but we will also offer an ECMA compliant
set of libraries.
Q: What does the name "Mono" mean?
A: Mono is the word for `monkey' in Spanish. We like monkeys.
Q: Is Mono usable?
A: The JIT engine is usable on Intel x86 machines. An interpreter
can be used on other non-Intel x86 machines.
The class libraries are mature enough to run some real applications
(the compiler for instance, and every day more and more applications
are natively developed with Mono).
Q: When will you ship it?
A: Different parts of Mono will achieve usability at different stages,
once we are comfortable with the compiler, we will release "Mono Core",
which contains everything needed to develop applications with the base
class libraries, this will happen soon and in the meantime you can
download daily snapshots of our work. Also the full ASP.NET support is
close to completion.
Other higher level class libraries (ASP.NET, ADO.NET, WinForms) will
be released when they become stable.
Q: What major components will you include in Mono?
A: Hopefully everything that Microsoft ships on their Framework
(ADO.NET, ASP.NET, WinForms), and we encourage third party developers to
create reusable components that work on both Mono and Windows.
Q: How can I contribute?
A: Check the contributing section.
Q: Aren't you just copying someone else's work?
A: We are interested in providing the best tools for programmers to
develop applications for Free Operating Systems. We also want to help
provide the interoperability that will allow those systems to fit in
with other standards.
For more background, read the Mono
Project white paper.
the project.
Q: Miguel said once that Mono was being implemented in COBOL. Is that true?.
A: No. It was a joke.
** The Ximian Role in the Mono Project
Q: Why is Ximian working on .NET?
A: Ximian is interested in providing the best tools for programmers to
develop applications for Free Operating Systems.
For more information, read the project rationale page.
Q: Will Ximian be able to take on a project of this size?
A: Of course not. Ximian a supporter of the Mono project, but the only way
to implement something of this size is for the entire free software
community to get involved. Visit the contributing
page if you'd like to help out.
Q: What pieces will Ximian be working on?
A: We will devote most of our resources to work on the pieces which are
on the critical path to release a development and execution
environment. Once the project is at a stage where it is useful in
the real world, it will achieve a critical mass of developers to
improve it further.
Q: Will Ximian offer Mono commercially?
A: When Mono is ready to be shipped Ximian will offer a commercial
support and services for Mono.
Q: Does Ximian provide consulting services around Mono?
A: Yes, Ximian does provide consulting services around Mono to
make it suitable to your needs. Porting the runtime engine,
customizing it, working on specific classes or tuning the code
for your particular needs.
Q: Will you wait until Mono is finished?
A: Mono will ship on various stages as they mature. Some people
require only a subset of the technologies, those will ship first.
More advanced features will take more time to develop. A support
time line will be available in June 2002.
** Mono and GNOME
Q: How is Mono related to GNOME?
A: In a number of ways. This project was born out of the need of
providing improved tools for the GNOME community, and will use
existing components that have been developed for GNOME when they
are available. For example, we plan to use Gtk+ and Libart to
implement Winforms and the Drawing2D API and are considering
GObject support.
Q: Has the GNOME Foundation or the GNOME team adopted Mono?
A: Mono is too new to be adopted by those groups. We hope that the
tools that we will provide will be adopted by free software
programmers including the GNOME Foundation members and the GNOME
project generally.
Q: Should GNOME programmers switch over to Mono now?
A: It is still far to early for discussions of "switching over." No
pieces of Mono will be ready within the next six months, and a
complete implementation is roughly one year away.
We encourage GNOME developers to continue using the existing tools,
libraries and components. Improvements made to GNOME will have an
impact on Mono, as they would be the "back-end" for various classes.
Q: Will Mono include compatibility with Bonobo components? What is the
relationship between Mono and Bonobo?
A: Yes, we will provide a set of classes for implementing and using
Bonobo components from within Mono. Mono should allow you to write
Bonobo components more easily, just like .NET on Windows allows you
to export .NET components to COM.
Q: Does Mono depend on GNOME?
A: No, Mono does not depend on GNOME. We use a few packages produced by
the GNOME team like the `glib' library.
Q: But will I be able to build GNOME applications?
A: Yes, we will enable people to write GNOME applications using Mono.
Q: Do you have C# bindings for GNOME?.
A: Yes, we currently bind libgnome, libgnomecanvas, and libgnomeui --
although I dare say I have no idea how functional the bindings are
outside of what I tested in the sample app. I imagine other libraries
under the GNOME framework will be added on an as-needed (and as-requested)
basis...although a truly good bonobo binding will have to wait on the CORBA
remoting support which has been started recently.
** GUI applications
Q: Will Mono enable GUI applications to be authored?
A: Yes, you will be able to build GUI applications. Indeed, that is our
main focus. We will provide both the Windows.Forms API and the Gtk# API.
Q: What is the difference between Gtk# and System.Windows.Forms?
A: Gtk# is a set of bindings for the Gtk+ toolkit for C# (and other
CIL-enabled languages). System.Windows.Forms is an API defined
by Microsoft to build GUI applications.
Q: Why not implement System.Windows.Forms on top of Gtk# or Qt#?
A: There are several reasons for this.
First of all, Gtk+ and Qt are standard toolkits on Linux, and their
proponents want to use their favorite toolkits when writing
applications.
Related to this is the idea that System.Windows.Forms is
brain-dead in certain areas, such as internationalization.
System.Windows.Forms uses explicit sizes for all controls, as opposed
to Gtk+ and Qt which use a box/packing model, which can better deal with
the different string lengths different languages will have.
Next is compatibility. It is not possible to implement
System.Windows.Forms on top of Gtk+/Qt and have 100% compatibility,
because System.Windows.Forms exposes lots of Win32-isms, such as the
Win32 message loop. In order to maintain compatibility, Wine must be used,
and this is being done; see the
System.Windows.Forms effort page.
Additionally, Wine apps don't currently fit in -- visually -- with
Gtk+ or Qt apps.
Q: Will I be able to run my smart clients on systems powered by Mono?
A: As long as your applications are 100% .NET and do not make use
of P/Invoke to call Win32 functions, your smart client applications
will run on Mono platforms.
Q: Where can I learn more about Gtk#?
A: The following
** Mono and Microsoft
Q: Is Microsoft helping Ximian with this project?
A: There is no high level communication between Ximian and Microsoft
at this point, but engineers who work on .NET or the ECMA groups
have been very friendly, and very nice to answer our questions, or
clarify part of the specification for us.
Microsoft is interested in other implementations of .NET and are
willing to help make the ECMA spec more accurate for this purpose.
Ximian was also invited to participate in the ECMA committee
meetings for C# and the CLI.
Q: Is Microsoft or Corel paying Ximian to do this?
A: No.
Q: Do you fear that Microsoft will change the spec and render Mono
useless?
A: No. Microsoft proved with the CLI and the C# language that it was
possible to create a powerful foundation for many languages to
inter-operate. We will always have that.
Even if changes happened in the platform which were undocumented,
the existing platform would a value on its own.
Q: Are you writing Mono from the ECMA specs?
A: Yes, we are writing them from the ECMA specs and the published
materials in print about .NET.
Q: If my applications use Mono, will I have to pay a service fee?
A: No. Mono is not related to Microsoft's initiative of
software-as-a-service.
Q: Is the Mono Project is related to the Microsoft Hailstorm effort? Is
Ximian endorsing Hailstorm?
A: No. The Mono Project is focused on providing a compatible set of
tools for the Microsoft .NET development platform. It does not
address, require, or otherwise endorse the MS Passport-based
Hailstorm single sign-on system that is part of Windows XP and
other services.
Q: Will Mono or .NET applications depend on Microsoft Passport?
A: No. MS Passport is unrelated to running .NET compatible applications
produced with the Mono tools. The only thing you will need is a
just-in-time compiler (JIT).
Q: What is a 100% .NET application?
A: A `100% .NET application' is one that only uses the APIs defined
under the System namespace and does not use PInvoke. These
applications would in theory run unmodified on Windows, Linux,
HP-UX, Solaris, MacOS X and others.
Q: If Microsoft will release a port of their .NET platform under the
`Shared Source' license, why should I bother with anything else?
A: The Shared Source implementation will be expensive and its uses
will be tightly restricted, especially for commercial use. We are
working towards an implementation that will grant a number of
important rights to recipients: use for any purpose,
redistribution, modification, and redistribution of modifications.
This is what we call Free Software
Q: Is Mono a free implementation of Passport?
A: No. Mono is just a runtime, a compiler and a set of class
libraries.
Q: Will the System.Web.Security.PassportIdentity class mean
that my software will depend on Passport?
A: No. Applications may use that API to contact a Passport site, but
are not required to do so.
As long as your application does not use Passport, you will not
need Passport.
Q: Will Mono running on Linux make Passport available for Linux?
A: No. However, the Passport toolkit for Linux-based web servers is
available from Microsoft.
Q: Will Mono allow me to run Microsoft Office on Linux?
A: No, it will not. Microsoft Office is a Windows application. To
learn more about running Windows applications on Intel Unix systems
refer to the Wine Project.
Q: Will I be able to compile a Microsoft VB.NET application and execute
the resultant MSIL file under MONO on Linux without converting to C#
and recompiling?
A: Once we have a complete VisualBasic runtime, yes.
Q: Can mono run the WebMatrix?
A: No. That requires System.Windows.Forms support which is not
currently implemented.
Q: Does mono have something like Passport?
Will mono have a server side Passport/Similar framework for XSP as well as client classes?
A: Not yet, but the client side API for authentication is not the problem.
We will likely have a lot of other authentication APIs, like the Liberty
Alliance APIs. The problem is people on the web provider end that might use
this for authentication.
** Mono Platforms
Q: What operating systems does Mono run on?
A: Mono is known to run on Linux, Unix and Windows systems.
Q: What architectures does Mono support?
A: Mono today ships with a Just-in-Time compiler for x86-based
systems. It is tested regularly on Linux, FreeBSD and Windows
(with the XP/NT core).
There is also an interpreter, which is slower that runs on the
s390, SPARC and PowerPC architectures.
Q: Can Mono run on Windows 9x, or ME editions?
A: Mono requires Unicode versions of Win32 APIs to run,
and only a handful of *W functions is supported under Win9x.
There is Microsoft Layer for Unicode that provides implementation
of these APIs on 9x systems.
Unfortunately it uses linker trick for delayed load that is not
supported by ld, so some sort of adapter is necessary.
You will need MSLU and one of the following libs to link Mono to
unicows.dll http://mono.eurosoft.od.ua/files/unimono.zip
or alternatively search the net for "libunicows".
No changes to Mono source code required, the only thing is to make
sure that linker will resolve imports to adapter library instead of
Win32 libs. This is achieved by inserting -lunimono before
-lkerner32/user32 in the linker's specs file.
** Mono and Portable.NET
Q: What are the differences between Mono and Portable.NET?
A: Most of Mono is being written using C#, with only
a few parts written in C (The JIT engine, the runtime, the
interfaces to the garbage collection system).
It is easier to describe what is unique about Mono:
- An advanced native-code compilation engine: Both
just-in-time compilation (JIT) and pre-compilation of CIL
bytecodes into native code are supported.
- A foundation for code optimization: The new code generator in
Mono builds on the experience of our first JIT engine, and enables
us to implement various advanced compiler optimization
tricks. With an SSA-framework, plenty of new optimizations are possible.
The current list of optimizations are: Peephole postpass,
Branch optimizations, Inline method calls, Constant folding, Constant
propagation, Copy propagation, Dead code elimination, Linear scan
global reg allocation, Conditional moves, Emit per-domain code,
Instruction scheduling, Intrinsic method implementations, Tail
recursion and tail calls, Loop related optimizations, Fast x86 FP
compares, Leaf procedures optimizations
- A self-hosting C# compiler written in C#, which is clean, easy
to maintain.
- Focus on the .NET Framework: we are tracking down the .NET
Framework API definition, as we believe it is the API people
will be most familiar with.
- A multi-platform runtime engine: both a JIT engine and an
interpreter exist. The JIT engine runs currently on x86
systems, while the interpreter works on SPARC, StrongARM,
s390 and PowerPC systems.
Our new compilation engine is being ported to the PowerPC.
- Supports Linux, BSD, Windows and Solaris at this point.
- The JIT engine is written using a portable instruction
selector which not only generates good code but
is also the foundation to re-target the JIT engine to other
systems.
- Full support for remoting in the runtime.
- The C# compiler, the JIT engine and the class libraries are
mature enough that the whole system has been self-hosting
since April 2002. This means that we develop Mono
completely with itself at this point.
By forcing ourselves to use our own code to develop our
tools, we bug fix problems rapidly, and the system is
overall more robust and tested than if we did not.
- We have a great community of developers, without which Mono
would not be possible.
** Web Services
Q: How is Mono related to Web Services?
A: Mono is only related to Web Services in that it will implement the
same set of classes that have been authored in the .NET Framework
to simplify and streamline the process of building Web Services.
But most importantly, Mono is an Open Source implementation of the
.NET Framework.
Q: Can I author Web Services with Mono?
A: You will be able to write Web Services on .NET that run on Mono and
vice-versa.
Q: If Mono implements the SDK classes, will I be able to write and
execute .NET Web Services with it?
A: Yes. When the project is finished, you will be able to use the
same technologies that are available through the .NET Framework SDK
on Windows to write Web Services.
Q: What about Soup? Can I use Soup without Mono?
A: Soup is a library for GNOME applications to create SOAP servers and
SOAP clients, and can be used without Mono. You can browse the
source code for soup using GNOME's Bonsai.
Q: Can I use CORBA?
A: Yes. The CLI contains enough information about a class that
exposing it to other RPC systems (like CORBA) is really simple, and
does not even require support from an object.
Remoting.CORBA is
a CORBA implementation that is gaining momentum.
Building an implementation of the Bonobo interfaces once this is ready
should be relatively simple.
Q: Can I serialize my objects to other things other than XML?
A: Yes, although the serializing tools have not yet been planned, and
you would probably have to implement them yourself.
Q: Will Mono use ORBit?
A: There are a few advantages in using ORBit, like reusing existing code
and leveraging all the work done on it. Michael Meeks has posted
a few reasons,
as well as some ideas
that could be used to reuse ORBit.
Most users are likely to choose a native .NET solution, like Remoting.CORBA
** MonoDoc
Q: What is MonoDoc?
A: MonoDoc is a graphical documentation browser for the Mono class
libraries. Currently, monodoc consists of a Gtk# application and is
in heavy development.
** Development Tools and Issues
Q: I am having trouble compiling a new version of Mono from CVS, it
complains about my runtime being out of sync.
A: Jonathan Pryor has provided the following answer:
To upgrade your class libraries and compiler, see the See
README.building in the MCS directory.
The single biggest source of confusion seems to be the "Your
runtime is out of sync" messages. Realize that this is *normal*
while BUILDING. Think about it: you're building a new class
library with the old runtime. If the new class library references
a function that the old runtime knows nothing about, the runtime
system issues this warning.
Basically what needs to happen is for a new mono runtime to be
compiled, then the corlib class library be compiled, and once this
is done, install the new runtime, followed by corlib.
Once this is done, you can continue building your entire
environment.
Q: Will it be possible to use the CLI features without using byte codes
or the JIT?
A: Yes. The CLI engine will be made available as a shared library.
The garbage collection engine, the threading abstraction, the
object system, the dynamic type code system and the JIT will be
available for C developers to integrate with their applications if
they wish to do so.
Q: Will you have new development tools?
A: With any luck, Free Software enthusiasts will contribute tools to
improve the developer environment. These tools could be developed
initially using the Microsoft implementation of the CLI and then
executed later with Mono.
Q: What kind of rules make the Common Intermediate Language useful for
JITers?
A: The main rule is that the stack in the CLI is not a general purpose
stack. You are not allowed to use it for other purposes than
computing values and passing arguments to functions or return
values.
At any given call or return instruction, the types on the stack
have to be the same independently of the flow of execution of your
code.
Q: Is it true that the CIL is ideal for JITing and not efficient for
interpreters?
A: The CIL is better suited to be JITed than JVM byte codes, but you
can interpret them as trivially as you can interpret JVM byte
codes.
Q: Isn't it a little bit confusing to have the name of "XSP" (the same
as in the Apache Project) for the ASP.NET support in Mono?.
A: In Mono, xsp is just the name of the C# code generator for ASP.NET
pages. In the Apache Project, it is a term for the "eXtensible Server
Pages" technology so as they are very different things, they don't
conflict.
Q: What about using something like Jabber instead of the System.Messaging
namespace?.
A: In short, MSMQ is not something like Jabber, but asynchronous messaging
through queues. Useful queues do more than serialize messages, they are
also platform bridges.
Q: Are you supporting XMLDocument and relatives?.
A: Currently, we aren't implementing them yet. It would require updates to
most of the XmlNode derivatives so it's not a trivial task. We are
currently focusing on getting XPath support working.
Q: Is there any plan to develop an aspx server for Mono?.
A: The web server turned out to be very simple compared to the rest of the
work. Gonzalo has got the page generator mostly done (a module called
xsp, who has nothing to do with the XSP term used in the Apache Project).
Patrik has done a lot of the work to get the ProcessRequest to work.
You can try to help in the final touches to the System.Web classes and
writing regression tests for the widgets we have.
Q: Is there any way I can develop the class libraries using Linux yet?
A: Yes. Some class libraries can be developed on Linux. Search for
Paolo's post (he lists which classes can be compiled fine now).
Q: Is there any way I can install a known working copy of mono in /usr,
and an experimental copy somewhere else, and have both copies use
their own libraries? (I'm still not very good at library paths in
Linux)
A: Yes. Just use two installation prefixes.
Q: How should I write tests or a tests suite?
A: If you do a test suite for C#, you might want to keep it
independent of the Mono C# compiler, so that other compiler
implementations can later use it.
Q: Would it be too terrible to have another corlib signed as mscorlib?
A: We rename corlib to mscorlib also when saving the PE files, in fact,
the runtime can execute program created by mono just fine.
Q: Is there a relatively straightforward way to repeat the steps taken
by Paolo to get Mono completely self-hosted on Linux?
A: To build the compiler and class libraries in Linux, run:
- make -f makefile.gnu. To install them, run:
- make -f makefile.gnu install prefix=/opt/mono
If you want to produce and distribute a monocharge tarball, run:
make -f makefile.gnu dist
Of course you have to run these in the top level mcs directory.
Q: Is it possible to build a C# file to some sort of intermediate format which
can linked into a final module, like the traditional .c -> .o -> .so path?
A: You could do: mcs /target:module file1.cs, mcs /target:module file2.cs,
mcs /target:exe file1.dll file2.dll /out:mybin.exe
Q: Is there any plans for implementing remoting in the near future?, When will
work in System.Runtime.Remoting.dll start?
A: The remoting infrastructure is in place. Some of the channels and
formatters are not.
Q: I'm wondering if there are any plans to start using nant to build the
class lib + test lib. i think that every project need/should use an
automated build process and nant + a couple of tools enables this. is
the problem that the compiler can't run nant yet?
A: Maybe well be doing some sort of automated build process + testing when
the summer finish.
Q: My C code uses the __stdcall which is not availble on Linux, how can I
make the code portable Windows/Unix across platforms?
A: Replace the __stdcall attribute with the STDCALL macro, and include this
in your C code for newer gcc versions:
#ifndef STDCALL
#define STDCALL __attribute__((stdcall))
#endif
** Mono and ASP.NET
Q: Does Mono support ASP.NET?
A: Yes.
Mono supports ASP.NET, we have shown an unmodified IBuySpy
installation running on Mono as well as various other programs. You can
try it yourself downloading the XSP server.
Q: Do I need install cygwin to work on ASP.NET in mono or Linux is enough since
it is self host right now.
A: Linux is enough.
Q: How can I run ASP.NET-based applications with Mono?
A: You need the Mono runtime and a hosting web server. Currently we distribute a
small web server called `xsp' which is used to debug applications, or you can choose
to use Daniel's Apache 2 module.
Q: Any plan to make ASP.NET in mono works with Apache in Linux?.
A: Daniel has authored an Apache2 Module for Mono that hosts the ASP.NET runtime
and is available here: http://apacheworld.org/modmono/
Q: Will you support Apache 1?
A: Modules developed for Apache 2 are not compatible with Apache 1.3
Daniel plans to support Apache 1.3 in the future but the current focus is on
Apache 2, because of the better support for threading and Windows.
Q: Can I run Apache 1 and Apache 2 on the same machine?
You can always keep a copy of Apache 2 running in paralell with your Apache
1.3 (either different port or using a reverse proxy).
You can also bind the two servers to different IP addresses on the
same physical machine.
** Mono and ADO.NET
Q: What is the status of ADO.NET support?. Could I start migrating
applications from MS.NET to Mono?.
A: You could start right now using the ADO.NET support in mono, of course,
if you want to help filling the missing gaps while you develop your app
:-) Well, what I mean is that we're not that far to having full ADO.NET
support in Mono, and we've got a lot of working things, so if we could
get more help, we'd finish it really soon :-)
Q: In developing the data architecture for the application are there and
objects I should stay away from in order to insure the smoothest possible
transition (minimum code rewrite) to Mono's ADO.NET implementation? (For
example, strongly typed datasets versus untyped datasets, etc...)
A: We are implementing all the classes in Microsoft .NET's System.Data, so
you can be sure that things will work the same in Mono as with the Microsoft
implementation.
Q: Does Mono can to connect to Sybase by using Mono.Data.*?
A: Yes. use Mono.Data.SybaseClient. First of all you have to create a
SybaseConnection, and then, from it, use it as any other
IDbConnection-based class.
** Mono and Java
Q: Why don't you use Java? After all, there are many languages that
target the Java VM.
A: You can get very good tools for doing Java development on free
systems right now. Red Hat has
contributed a GCC front-end for Java that can take
Java sources or Java byte codes and generate native executables; Transvirtual has implemented
Kaffe a JIT engine for Java;
Intel also has a Java VM called ORP.
The JVM is not designed to be a general purpose virtual machine.
The Common Intermediate Language (CIL), on the other hand, is
designed to be a target for a
wide variety of programming languages, and has a set of rules
designed to be optimal for JITers.
Q: Could Java target the CLI?
A: Yes, Java could target the CLI, Microsoft's J# compiler does that.
The IKVM project builds a
Java runtime that works on top of .NET and on top of Mono. IKVM is
essentially a JIT compiler that translates from JVM bytecodes into
CIL instructions, and then lets the native JIT engine take over.
Q: Is it possible to write a JVM byte code to CIL converter?
A: Yes, it is possible. Here are a few starting point:
* A byte code representation is really a flattened forest of
trees. Look at the Mono JIT engine to see how we compute
the basic blocks (this is used to figure out the "trees").
The forest is just an array of trees.
Indeed, run the JIT engine with -d (mono -d prog.exe) and
you will see how these trees look like.
You will have to do something similar for Java.
* Each "forest of trees" has a meaning. This meaning can now
be translated into the equivalent "meaning" in CLR-land.
See also the IKVM project
Q: Could mono become a hybrid CIL/java platform?
A: No. It is quite far from the philosophy of the project. The idea of Mono
is, to have only _one_ VM, on which all can run. And if there existing a
binary-converter from Java-.class to IL and if there existing something
like J-Sharp on Mono, you can write programs in Java, which than can run
on Mono. You do not need two bindings (like your example: GTK-Sharp _and_
Java-Gnome). You need only _one_ of it (GTK-Sharp). Thats the idea of Mono.
An other point is, that there are no people, who use Open Source-JVMs. They
all prefer Suns original. But for Unix there don't exist a .NET-Framework.
So it is possible, that in the future Mono is the standard .NET for Unixes.
Q: Do you plan to implement a Javascript compiler?
A: Yes. The beginnings of the JScript compiler can be found on CVS.
Cesar coordinates this effort.
Q: Can Mono or .NET share system classes (loaded from mscore.dll and other
libs) or will it behave like Sun's Java VM?
A: What you can do with mono is to load different applications in their own
application domain: this is a feature of the CLR that allows sandboxing
applications inside a single process space. This is usualy exploited to
compartmentalize different parts of the same app, but it can also be
effectively used to reduce the startup and memory overhead.
Using different appdomains the runtime representation of types and
methods is shared across applications.
** Extending Mono
Q: Would you allow other classes other than those in the
specification?
A: Yes. The Microsoft class collection is very big, but it is by no
means complete. It would be nice to have a port of `Camel' (the
Mail API used by Evolution inspired by Java Mail) for Mono
applications.
You might also want to look into implementing CORBA for Mono. Not
only because it would be useful, but because it sounds like a fun
thing to do, given the fact that the CLI is such a type rich
system.
For more information on extending Mono, see our ideas page.
Q: Do you plan to Embrace and Extend .NET?
A: Embracing a good technology is good. Extending technologies in
incompatible ways is bad for the users, so we do not plan on
extending the technologies.
If you have innovative ideas, and want to create new classes, we
encourage you to make those classes operate correctly well in both
Mono and .NET.
Today Mono ships with a number of extra libraries that were
developed either by members of the Mono community, or other
groups.
Q: Is there any way I can develop the class libraries using Linux yet?
A: Yes. Mono has been selfhosting since March 2002.
Q: Is there any way I can install a known working copy of mono in /usr,
and an experimental copy somewhere else, and have both copies use
their own libraries? (I'm still not very good at library paths in
Linux)
A: Yes. Just use two installation prefixes.
** Portability
Q: Will Mono only work on Linux?
A: Currently, we are doing our work on Linux-based systems and
Windows. We do not expect many Linux-isms in the code, so it
should be easy to port Mono to other UNIX variants.
Q: What about Mono on non Linux-based systems?
A: Our main intention at Ximian is to be able to develop GNOME
applications with Mono, but if you are interested in providing a
port of the Winforms classes to other platforms (frame buffer or
MacOS X for example), we would gladly integrate them, as long
they are under an open source license.
Q: What operating systems/CPUs do you support
A: Mono currently runs on Linux, Windows, Solaris and FreeBSD.
There is a JIT engine available for x86 processors that can
generate code and optimizations tailored for a particular CPU.
Interpreters exist for the SPARC, PowerPC and StrongARM CPUs.
Q: Does Mono run on Windows?
A: Yes. You can get pre-compiled
binaries from http://www.go-mono.com/download.html
Q: Does Mono run on Linux?
A: Yes. You can get pre-compiled
binaries from http://www.go-mono.com/download.html
Q: Will I require Cygwin to run mono?
A: No. Cygwin is only required to build Mono.
Q: Will Mono depend on GNOME?
A: It will depend only if you are using a particular assembly (for
example, for doing GUI applications). If you are just interested
in Mono for implementing a `Hello World Enterprise P2P Web
Service', you will not need any GNOME components.
Q: Is anyone working on porting Mono to IA-64?
A: Nobody is working on such port.
Q: If I were about to start a Mono port to IA-64,would the same lburg code
generator work for IA-64 also? or anything else need to be used for code
generation(as the processor architecture is totally different from IA32)
A: The lburg approach can be use for any processor architecture. But you might
think in another better approach.
Q: Do you plan to port Rhino to C#?.
A: Eto Demerzal has started a Rhino port to C#.
Q: Has anyone succeeded in building a Mac version of the C# environment.
If so can you explain how?
A: You could try to check with the Darwin people, or the Fink people.
Mono/C# is self hosting on Linux/PPC which is the hard part, so it
should be relatively simple to get it to work on MacOS
** Reusing Existing Code
Q: What projects will you reuse or build upon?
A: We want to get Mono in the hands of programmers soon. We are
interested in reusing existing open source software.
Q: What about Intel's research JIT framework, ORP?
A: At this time, we are investigating whether we can use elements of
ORP for Mono. ORP is a research JIT engine that has a clearly
defined API that splits the JIT from the GC system and the actual
byte code implementation.
We are using some pieces of ORP (Their code generation interface)
and we use it as a source of inspiration for optimizations. Paolo
and Dietmar consider ORP as being one of the best JIT engines out
there (and their research work and papers are very useful if you are
interested in JIT technology).
Q: What about using GNU Lightning?
A: We are not using GNU Lightning. Our JIT is using an instruction
selector based on tree-pattern matching, and a code generation
interface that is very tied to the current architecture.
Q: Will I be able to use Microsoft SQL Server 2000 or will I need to switch
to a specific Open Source Database. Will I need to recode?
A: There should not be any need to recode.
Q: What do I need to watch out for when programming in VB.NET so that I'm
sure to be able to run those apps on Linux?
A: Not making any PInvoke or DLL calls should and not using anything in
the Microsoft.* namespaces should suffice. Also do not use any
Methods/Classes marked as "This type/method supports the .NET Framework
infrastructure and is not intended to be used directly from your code."
even if you know what these classes/methods do.
Q: Will built-in reporting be supported for crystal reports? This is a
heavily used part of our system.
A: Probably not. Crystal Reports are propriety. Someone may try to emulate
the behavior, but no-one has yet volunteered.
Q: Who about writing to the registry? As I understand it, Linux does not have
a counterpart to the registry. Should I avoid relying on that feature?
A: Try to avoid it. Although there would be a emulation for registry in
Mono too. GNOME does have a registry like mechanism for configuration. But
Even if gnome has a configuration system similar to the registry, the keys
will not be equal, so you will probably end up having to do some runtime
detection, and depending on this load an assembly that has your
platform-specific hacks.
Q: System.Data.SqlClient with FreeTDS, will you port parts of these to C# and
use them?
A: if their license is compatible with mono's, yes, we'd think about porting
them. If not, we'll continue with the plan of using FreeTDS.
** Mono and GCC
Q: Are you working on a GCC front-end to C#? A GCC back-end that will
generate CIL images? What about making a front-end to GCC that
takes CIL images and generates native code?
A: We are currently seeking volunteers for those projects.
Visit the contributing section if
you are interested.
Q: But would this work around the GPL in the GCC compiler and allow
people to work on non-free front-ends?
A: People can already do this by targeting the JVM byte codes (there
are about 130 compilers for various languages that target the JVM).
Q: Why are you writing a JIT engine instead of a front-end to GCC?
A: We want the JIT engine and runtime engine because they will be able
to execute CIL executables generated on Windows, and so no recompilation
will be necessary.
** Performance
Q: How fast will Mono be?
A: We can not predict the future, but a conservative estimate is that
it would be at least `as fast as other JIT engines'.
We would like to ship various JIT engines with Mono, just like
Microsoft has done with their .NET development platform. We could
provide a faster, JIT for fast load times but lower performance,
and an and an optimizing JIT that would be slower at generating
code but produce more optimal output.
The CIL has some advantages over the Java byte code: it is really
an intermediate representation and there are a number of
restrictions on how you can emit CIL code that simplify creating
better JIT engines.
For example, on the CIL, the stack is not really an abstraction
available for the code generator to use at will. Rather, it is a
way of creating a postfix representation of the parsed tree. At
any given call point or return point, the contents of the stack are
expected to contain the same object types independently of how the
instruction was reached.
** Licensing
Q: Will I be able to write proprietary applications that run with
Mono?
A: Yes. The licensing scheme is planned to allow proprietary
developers to write applications with Mono.
Q: What license or licenses are you using for the Mono Project?
A: The C# Compiler is released under the terms of the GNU GPL. The runtime
libraries are under the GNU
Library GPL. And the class libraries are released
under the terms of the MIT X11
license.
The Mono runtime and the Mono C# Compiler are also available under
a proprietary license for those who can not use the LGPL and the
GPL in their code.
For licensing details, contact mono-licensing@ximian.com
Q: I would like to contribute code to Mono under a particular
license. What licenses will you accept?
A: We will have to evaluate the licenses for compatibility first,
but as a general rule, we will accept the code under the same
terms of the "container" module.
** Patents
Q: Could patents be used to completely disable Mono (either submarine
patents filed now, or changes made by Microsoft specifically to
create patent problems)?
A: First some background information.
The .NET Framework is divided in two parts: the ECMA/ISO covered
technologies and the other technologies developed on top of it like
ADO.NET, ASP.NET and Windows.Forms.
Mono implements the ECMA/ISO covered parts, as well as being a
project that aims to implement the higher level blocks like
ASP.NET, ADO.NET and Windows.Forms.
The Mono project has gone beyond both of those components and has
developed and integrated third party class libraries, the most
important being: Debugging APIs, integration with the Gnome
platform (Accessibility, Pango rendering, Gdk/Gtk, Glade, GnomeUI),
Mozilla, OpenGL, extensive database support (Microsoft only
supports a couple of providers out of the box, while Mono has
support for 11 different providers), our POSIX integration
libraries and finally the embedded API (used to add scripting to
applications and host the CLI, or for example as an embedded
runtime in Apache).
The core of the .NET Framework, and what has been patented by
Microsoft falls under the ECMA/ISO submission. Jim Miller at
Microsoft has made a statement on the patents covering ISO/ECMA,
(he is one of the inventors listed in the patent): here.
Basically a grant is given to anyone who want to implement those
components for free and for any purpose.
The controversial elements are the ASP.NET, ADO.NET and
Windows.Forms subsets. Those are convenient for people who need
full compatibility with the Windows platform, but are not required
for the open source Mono platform, nor integration with today's
Mono's rich support of Linux.
The Mono strategy for dealing with these tehcnologies is as
follows: (1) work around the patent by using a different
implementation techinque that retains the API, but changes the
mechanism; if that is not possible, we would (2) remove the pieces
of code that were covered by those patents, and also (3) find prior
art that would render the patent useless.
Not providing a patented capability would weaken the
interoperability, but it would still provide the free software /
open source software community with good development tools, which
is the primary reason for developing Mono.
The patents do not apply in countries where software patents are
not allowed.
For Linux server and desktop development, we only need the ECMA
components, and things that we have developed (like Gtk#) or Apache
integration.
** Miscellaneous Questions
Q: You say that the CLI allows multiple languages to execute on the
same environment. Isn't this the purpose of CORBA?
A: The key difference between CORBA (and COM) and the CLI is that the
CLI allows "data-level interoperability" because every
language/component uses the same data layout and memory management.
This means you can operate directly upon the data types that someone
else provides, without having to go via their interfaces. It also
means you don't have to "marshal" (convert) parameters (data
layouts are the same, so you can just pass components directly) and
you don't have to worry about memory management, because all
languages/components share the same garbage collector and address
space. This means much less copying and no need for reference
counting.
Q: Will you support COM?
A: The runtime will support XPCOM on Unix systems and COM on Windows.
Most of the code for dynamic trampolines exists already.
Q: Will Ximian offer certifications on Mono or related technologies?.
A: It's possible. But there is no plan about this. So the short answer is no.
Q: Are there any Boehm's GC binaries?
A: Yes. You can find RPMs here, though
if your distribution provides the correct packages, you should use those.
The suggested version of the Boehm GC is 6.1.
Q: How can I report a bug?
A: The best thing is to track down the bug and provide a simple test to
reproduce the bug. You can then add the bug to the
bugtracking system.
Please provide information about what version of mono you're using
and any relevant details to be able to reproduce the bug. Note that
bugs reported on the mailing-list may be easily forgotten, so it's
better to file them in the bug tracking system.
Q: Does mcs support the same command line options as the MS C#
compiler?
A: The Mono C# compiler now supports the same command line
arguments as the Microsoft C# compiler does.
Q: How about getting searchable archives on lists.ximian.com?
A: You can perform a search on the mono-related mailing lists
here.
Q: When using mono from cvs or from a snapshot, I get an error messaage
saying that Mono and the runtime are out of sync. How do I fix that?
A: If you use mono from cvs, you need to be prepared for changes in the
runtime internals. This means that you should keep a working setup
before blindling updating (a working setup may just be the last released
tarball or a recent binary snapshot).
Usually, compiling corlib with mcs before recompiling the C runtime does
the right thing (but occasionally you may need to do it the other
way around).
Q: Why are you going for a GtkHtml implementation?
A: GtkHTML is just a lightweight HTML rendering engine that does not
support CSS, so we need it to look decent for those of us that will
be using the documentation in our day-to-day work on Linux. The
Web-based interfaces lack the agility that you get from a native GUI
tool to browse your documentation. Probably later on, we will write
scripts and generate a full documentation set that is web-browsable,
but we need a command-line and GUI tools that we can use natively on
Linux when disconnected from the Web (and that has better
interactions than a web page).
Q: Is there a command-line tool that allows me to access .NET interactively?
A: There are several but one that is free software and uses MCS is the one
Dennis Lu from Rice University is working on; a REPL C# interpreter.
Q: Is it possible to use Visual C++ with Mono?.
A: It's possible to run VC++ generated apps under Mono, but we do not
provide a Manager C++ compiler ourselves.
** Mono Common Problems
If you are having problems compiling or running Mono software
or if you think that you found a bug, etc. Please visit the
Mono Common Problems document and try there.