Changelog

Release history and notable changes in Shed Skin

All notable changes to Shed Skin are documented here. The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

Unreleased

Upcoming changes that will be in the next release.

Fixed

• Fixed dict comprehension code generation crash (TypeError: 'Tuple' object is not subscriptable) in cpp.py by accessing node.elt.elts[0]/node.elt.elts[1] instead of node.elt[0]/node.elt[1]
• Fixed dict comprehension type inference in graph.py: isinstance(node.elt, tuple) was always False for ast.Tuple nodes, so key/value type constraints were never set up. Changed to node in self.gx.dictcomp_to_lc.values()
• Fixed runtests --run executing unbuilt ext tests by aligning ctest regex with the build target suffix in cmake.py
• Added missing WORKING_DIRECTORY for non-Windows ext tests in CMake configuration

Changed

• Converted build system to uv, replacing pip/setuptools workflow with uv commands in Makefile
• Applied mypy strict mode fixes across core modules (__init__, cmake, config, cpp, graph, infer, makefile, stats)
• Converted documentation from Sphinx/RST to MkDocs with Markdown
  • Replaced README.rst with README.md
  • Removed generated Sphinx HTML/JS/CSS assets from docs/
  • Added mkdocs.yml configuration
• Updated Makefile test target to fix test invocation
• Refactored graph.py and infer.py to resolve type issues

Removed

• Removed requirements.txt (dependencies now managed via pyproject.toml and uv)

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[0.9.12] - 2024

Major release introducing local dependency management and significant internal refactoring.

Added

Local Dependency Management

Starting with 0.9.12, --local-deps is now the default dependency manager, eliminating the need for external package managers.

• Local dependency management (--local-deps flag) with bundled zip archives:
  • Builds bdwgc and pcre2 from compressed sources in shedskin/ext/
  • Extracts to platform-specific cache on first use:
    • macOS: ~/Library/Caches/shedskin/
    • Linux: ~/.cache/shedskin/
    • Windows: %LOCALAPPDATA%/shedskin/Cache/
  • Caches built static libraries for subsequent compilations
  • Works completely offline (no network required)
  • Cross-platform support (Linux, macOS, Windows)
• LocalDependencyManager class in cmake.py for zip-based dependency building
• CLI option --local-deps for both translate (Makefile) and build (CMake) commands

Testing

• Unit tests for core modules (tests/unit/, 74 tests total):
  • test_config.py: Tests for GlobalInfo and state objects
  • test_graph.py: Tests for constraint graph building
  • test_infer.py: Tests for type inference
  • test_cpp.py: Tests for C++ code generation config

Changed

Dependency Management

• Made --local-deps the default dependency manager for build, run, and runtests subcommands
  • Dependencies are now automatically built from bundled ext/ sources
  • No external package manager required out of the box
• Bundled bdwgc (v8.2.10) and pcre2 (pcre2-10.47) sources as compressed zip archives in ext/:
  • Reduced from 25MB (full sources) to 1.2MB (trimmed and compressed)
  • Removed documentation, tests, CI/CD files, autotools, legacy platform support
  • Removed SLJIT (JIT compiler) from pcre2 as Shed Skin doesn’t use JIT features
• Simplified CMake output directories to ${CMAKE_BINARY_DIR} (executables in build/)

Architecture Refactoring

• Refactored GlobalInfo class into focused state objects for better code organization:
  • FileSystemPaths: Immutable paths for shedskin installation, resources, and libraries
  • BuildConfiguration: Build flags (bounds_checking, int32/64, nogc, etc.)
  • NamingContext: C++ keywords, prefix, and builtin type names
  • EntityRegistry: Functions, classes, variables, modules, and inheritance tracking
  • GraphBuildingContext: Temporary graph building state (loops, comprehensions, etc.)
  • TypeInferenceState: Core type inference data (cnode, types, constraints, etc.)
• Created new shedskin/state/ package containing the focused state dataclasses
• Maintained 100% backwards compatibility via property delegation in GlobalInfo

CLI Improvements

• Consolidated CLI argument definitions using argparse parent parsers:
  • Created _create_shared_parsers() method with reusable argument groups
  • Shared parsers: stats, types, disable, compiler, cmake
  • Reduced code duplication across translate, build, run, runtests subcommands

Security

• Replaced os.system() with subprocess.run() across all modules:
  • cmake.py: shellcmd, cmake config/build/test, pytest
  • makefile.py: Command execution in _execute()
  • __init__.py: Executable running and Windows color output hack

Documentation

• Documented type inference tuning constants in infer.py:
  • INCREMENTAL: Enable incremental analysis mode
  • INCREMENTAL_FUNCS: Functions to add per round (default: 5)
  • INCREMENTAL_DATA: Enable incremental allocation tracking
  • INCREMENTAL_ALLOCS: Allocations before restart (default: 1)
  • MAXITERS: Maximum iterations per round (default: 30)
  • CPA_LIMIT: Initial cartesian product limit (default: 10)
• Added MAX_TYPE_DEPTH constant in typestr.py for recursion limit (default: 10)

Fixed

• Fixed CMake build failure when source file path is absolute (e.g., building from a different directory with ../examples/foo.py). The issue occurred because absolute parent paths were being concatenated with build directories, creating invalid paths like build/exe/C:/Users/.../file.cpp
• Resource leaks: Added context manager support to MakefileWriter class
• File handling: Use context managers for file operations in config.py

Removed

• Removed Conan dependency manager support:
  • Removed --conan CLI option
  • Removed ConanBDWGC, ConanPCRE, and ConanDependencyManager classes
  • Removed ENABLE_CONAN CMake option
  • Removed shedskin/resources/conan/ directory
  • Removed conan from requirements.txt

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Version History

Shed Skin has been in development since 2005. Version 0.9.12 represents a significant milestone in maturity and usability.

Key Milestones

• 2005: Initial release by Mark Dufour
• Various versions: Gradual improvements in type inference, optimization, and library support
• 0.9.x series: Focus on stability, usability, and modern Python 3 support
• 0.9.12 (2024): Major architectural improvements and simplified dependency management

Performance Evolution

Shed Skin has consistently improved performance over the years:

Sieve benchmark (n=100000000):

CPython 3.10.6:     13.4 seconds
CPython 3.11.0:     11.4 seconds
Nuitka 0.6.16:      11.4 seconds
PyPy 3.9.12:         5.8 seconds
Numba 0.56.4:        2.5 seconds
Shed Skin 0.9.9:     1.9 seconds
Shed Skin 0.9.9:     1.8 seconds (with --nowrap --nobounds)

Note: Numba defaults to int64 as integer type, while Shed Skin defaults to int32. Performance is practically equal when using shedskin --int64.

Example Programs

Shed Skin successfully compiles over 80 non-trivial programs (at over 25,000 lines in total), including:

• Games: DOOM, Othello, Quake, C64 emulator
• Graphics: Ray tracer, Voronoi diagrams, 3D rendering
• Algorithms: A*, neural networks, genetic algorithms
• Utilities: rsync-like tool, SHA implementations

See the Examples section for more details.

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Contributing

Shed Skin is open source and welcomes contributions! See Contributing for how to get involved.

Reporting Issues

Found a bug or have a feature request? Open an issue on GitHub.

Source Code

View the source code and full commit history on GitHub.