An overview of the SSCLI Distribution

1. An overview of the SSCLI Distribution Mark Lewin Microsoft Research marklew@microsoft.com

2. Stats for SSCLI Archive(approximate as of 27 March 2002) • Packaged as single compressed file archive • 1.9 million lines of code • 1.15M of C and C++ • 625K of C# • 125K of CIL (intermediate language) • Smattering of assembly code • 5900 source files (9700 total) • 2900 tests • Build output • 1200 defined types • About 20 dynamically loadable libraries • About 22 executable programs

3. The Lay of the Land • Four major areas in source code • Runtime “execution engine” • Frameworks • Compilers and tools • Portability layer, tests, and build infrastructure • Other important points of interest • License • Documentation • Samples

4. Root Directory: License & Doc • Shared source license • Allows for non-commercial redistribution of both binary and source, including modified versions • Simple restrictions (primarily non-commercial use) • READFIRST.html • Points to relnotes.html with late breaking items • Points to docs/index.html • Also important, but not included: • ECMA specifications • Microsoft .NET Frameworks SDK

5. Area #1: Execution Engine • Heart of component-oriented infrastructure • Converts metadata, resources, and CIL (on disk as PE/COFF image) into running code • Great interoperability with “unmanaged code” • JIT compilation and IL verification • Cross-language exception handling • Language-agnostic, object-capable, type system • Automatic heap and stack management • Dynamic code loading • Evidence-based security (code access security)

6. Look For: PE Reading/Writing • “Portable Executable” format • Based on PE/COFF (see ceefilegen for details) • Uses existing extension mechanism • Three kinds of CLI data: metadata, CIL instructions, resources • Persistent packaging for types • Methods include stack frame size, types of local variables and parameters, pinned variable info, and exception handler table • Powerful metadata extensibility • Logical components as “assemblies” • Enforced security boundary, see fusion for binding logic • Also contains refs to other assemblies and version info • Cryptographic “strong names” an option (required for sharing)

7. Look For: Metadata Facilities • Metadata is heart of CLI execution model • Metadata interwoven with instruction set • Read-only PE pages shared between processes • Tokens used for addressing metadata • Data stored in tables (heaps when variable length) • Tokens are concatenated table + record number • Optimized for load time at expense of generation complexity/speed; compact within these parameters • Three levels of API • Reflection for managed code • Both internal and external API for C/C++, see md

8. Look For: CIL • Basis for most managed code execution in the CLI • Simple stack machine model – see vm directory • Typeless opcodes defined in opcodes.def • Verifiable subset – see fjit directory for verification • Signed and unsigned via opcode, not type • CIL code is JIT compiled to run under CLI management • Type layout, control, and dispatching • Typed variable argument lists, dynamically typed pointers • Tail calls, virtual dispatch, call via function pointer • Rich set of conversion operations, calling conventions, interop • Exception handling (two-pass) • Garbage collection

9. Area #2: Frameworks • A “minimal toolkit” for the 21st century programmer • Base class library • Collections, arrays, strings, and other compound datatypes • Globalization and formatting • System services (threads, I/O, synchronization, etc.) • Security • Floating point and extended arrays libraries • Networking, regular expressions, and XML libraries • Includes access to runtime infrastructure • Reflection and custom attributes • Remoting, unmanaged interop, serialization, and marshaling • AppDomains, Assemblies, GC, other execution engine features

10. Area #3: Compilers and Tools • Full-featured C# compiler (also used in build) • JScript compiler written entirely in C# • Additional developer tools • clix, the shared source CLI program launcher • Assembly tools: resource compiler, assembly linker, metainfo metadata viewer, assembler, disassembler • Debuggers: cordbg managed debugger, plus a debug extension for working on managed code from C/C++

11. Unified type system (boxing) Extensible attributes Properties Events Indexers struct types Enumeration types Delegate types override Unsafe code Conditional methods Interop (parameter marshaling) Multi-dimensional arrays Operator overloading User-defined conversions Variable parameter lists ref and out parameters Unsigned types Decimal type Conditional compilation foreach statement Overflow checking Explicit interface implementations Interesting C# Features to Examine

12. Area #4: Build, Port, & Test • Platform Adaptation Layer (PAL) in pal directory • System resources all consumed via PAL • Less than 250 partially complete Win32 APIs • Missing system features layered into PAL on any given platform • “PAL runtime” contains shared code for upper level tools • Good specification can be found in pal_guide.html • Loading and teardown of context • Threading model, scheduling, and timers • Synchronous file I/O, asynchronous network I/O • Synchronization (critsec, mutex, semaphore, events) • Debugging and tool support • Additional work for port: • JIT (very portable 3 layer macro emitter design) • Small amount of assembly code in execution engine

13. Build Infrastructure and Utilities • Build scripts and programs • Scripts for environment setup and build • build, binplace, nmake, and resource compiler utilities • Utility configuration programs • gacutil – manage the “global assembly cache” • sn – manage assembly signing • peverify – verify CIL in an assembly • caspol – modify policy for “code access security” • storeadm – manage “isolated storage”

14. Build Bootstrap Process • Initial phase • Build PAL using native toolchain • Build build tools against PAL • Complete by building resource compiler and PAL runtime using newly compiled build tools • Main phase has complex interdependencies • Unmanaged frameworks, compilers, and tools, are built • Managed portions of runtime and frameworks are built • Assemblies and runtime are configured • Finally, when managed portions are used at runtime, they are, of course, JIT compiled

15. Tests • Incredibly handy when modifying code! • Two major areas: managed code and PAL • PAL suites • Test driver script is pvtun.pl • Can be used on new PAL implementations • Quality suites • Test driver script is rrun.pl • Three primary areas in this release • IL verification • “BVT” smoke tests – many small programs • Tests for the BCL

16. Additional Resources • ECMA specs: http://msdn.microsoft.com/net/ecma • Microsoft commercial C# and CLR SDK http://msdn.microsoft.com/downloads • Shared source info: http://www.microsoft.com/sharedsource