An overview of the SSCLI Distribution

1
An overview of the SSCLI Distribution

• Mark Lewin
• Microsoft Research
• marklew_at_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

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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

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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

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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)

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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)

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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

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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

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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

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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

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Interesting C Features to Examine

• 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

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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

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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

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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

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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

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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