* MCS: The Ximian C# compiler
- MCS began as an experiment to learn the features of C# by
- writing a large C# program. MCS is currently able to parse C#
- programs and create an internal tree representation of the
- program. MCS can parse itself.
+ The Mono C# compiler is considered feature complete at this
+ point and relatively mature. MCS is able to compile itself
+ and many more C# programs (there is a test suite included that
+ you can use). It is routinely used to compile Mono, roughly
+ half a million lines of C# code.
- Work is progressing quickly on various fronts in the C#
- compiler. Recently I started using the System.Reflection API
- to load system type definitions and avoid self-population of
- types in the compiler and dropped my internal Type
- representation in favor of using the CLI's System.Type.
+* Pending tasks
+
+ There are a few known bugs in the Mono C# compiler, but
+ they are very very few at this point,
+ you can also browse the MCS <a href="http://bugzilla.ximian.com/buglist.cgi?product=Mono%2FMCS&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&email1=&emailtype1=substring&emailassigned_to1=1&email2=&emailtype2=substring&emailreporter2=1&changedin=&chfieldfrom=&chfieldto=Now&chfieldvalue=&short_desc=&short_desc_type=substring&long_desc=&long_desc_type=substring&bug_file_loc=&bug_file_loc_type=substring&keywords=&keywords_type=anywords&op_sys_details=&op_sys_details_type=substring&version_details=&version_details_type=substring&cmdtype=doit&newqueryname=&order=Reuse+same+sort+as+last+time&form_name=query">bugs</a> from Bugzilla.
+
+ A test suite is maintained to track the progress of
+ the compiler and various programs are routinely compiled and
+ ran.
+
+** Slides
+
+ Slides for the Mono C# Compiler presentation at .NET ONE are
+ available <a
+ href="http://primates.ximian.com/~miguel/slides-europe-nov-2002/Mono_C_Sharp_Overview_1007.sxi">here</a>
+ in StarOffice format.
+
+** Obtaining MCS
+
+ The Mono C# compiler is part of the `mcs' module in the Mono CVS
+ you can get it from our <a href="anoncvs.html">Anonymous CVS</a> server,
+ or you can get nightly <a href="download.html">download page</a>.
+
+** Running MCS
+
+ MCS is written in C# and uses heavily the .NET APIs. MCS runs
+ on Linux with the Mono runtime and on Windows with both the
+ .NET runtime and the Mono runtime.
+
+** Reporting Bugs in MCS
+
+ When you report a bug, try to provide a small test case that would
+ show the error so we can include this as part of the Mono C# regression
+ test suite.
+
+ If the bug is an error or a warning that we do not flag, write
+ a sample program called `csXXXX.cs' where XXXX is the code number
+ that is used by the Microsoft C# compiler that illustrates the
+ problem. That way we can also do regression tests on the invalid
+ input.
** Phases of the compiler
have to postpone this decision until the above steps
are finished.
- * Code generation: nothing done so far, but I do not
- expect this to be hard, as I will just use
- System.Reflection.Emit to generate the code.
-
+ * Code generation: The code generation is done through
+ the System.Reflection.Emit API.
</ul>
-<a name="tasks">
-** Current pending tasks
+** CIL Optimizations.
- Simple tasks:
+ The compiler performs a number of simple optimizations on its input:
+ constant folding (this is required by the C# language spec) and
+ can perform dead code elimination.
- <ul>
- * Array declarations are currently being ignored,
+ Other more interesting optimizations like hoisting are not possible
+ at this point since the compiler output at this point does not
+ generate an intermediate representation that is suitable to
+ perform basic block computation.
- * PInvoke declarations are not supported.
+ Adding an intermediate layer to enable the basic block
+ computation to the compiler should be a simple task, but we
+ are considering having a generic CIL optimizer. Since all the
+ information that is required to perform basic block-based
+ optimizations is available at the CIL level, we might just skip
+ this step altogether and have just a generic IL optimizer that
+ would perform hoisting on arbitrary CIL programs, not only
+ those produced by MCS.
- * Pre-processing is not supported.
+ If this tool is further expanded to perform constant folding
+ (not needed for our C# compiler, as it is already in there)
+ and dead code elimination, other compiler authors might be
+ able to use this generic CIL optimizer in their projects
+ reducing their time to develop a production compiler.
- * Attribute declarations and passing currently ignored.
+** History
- * Compiler does not pass around line/col information from tokenizer for error reporting.
+ MCS was able to parse itself on April 2001, MCS compiled itself
+ for the first time on December 28 2001. MCS became self hosting
+ on January 3rd, 2002.
- * Jay does not work correctly with `error'
- productions, making parser errors hard to point. It
- would be best to port the Bison-To-Java compiler to
- become Bison-to-C# compiler (bjepson@oreilly.com
- might have more information)
- </ul>
-
- Interesting and Fun hacks to the compiler:
-
- <ul>
- * Finishing the JB port from Java to C#. If you are
- interested in working on this, please contact Brian
- Jepson (bjepson at oreilly d-o-t com).
-
- More on JB at: <a href="http://www.cs.colorado.edu/~dennis/software/jb.html">
- http://www.cs.colorado.edu/~dennis/software/jb.html</a>
-
- JB will allow us to move from the Berkeley Yacc
- based Jay to a Bison-based compiler (better error
- reporting and recovery).
-
- * Semantic Analysis: Return path coverage and
- initialization before use coverage are two great
- features of C# that help reduce the number of bugs
- in applications. It is one interesting hack.
-
- * TypeRefManager. This exists currently in its infancy only.
-
- * Enum resolutions: it is another fun hack, as enums can be defined
- in terms of themselves (<tt>enum X { a = b + 1, b = 5 }</tt>).
-
- </ul>
+ The Mono Runtime and the Mono execution engine were able to make
+ our compiler self hosting on March 12, 2002.
** Questions and Answers
We will do this through an implementation of the CLI Virtual
Execution System for Unix (our JIT engine).
+ Our JIT engine is working for the purposes of using the compiler.
+ The supporting class libraries are being worked on to fully support
+ the compiler.
+
Q: Do you use Bison?
A: No, currently I am using Jay which is a port of Berkeley Yacc to
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